THE BEAMING SUN: 

 THE EFFECTIVENESS OF IMPERIAL JAPANESE RADAR  

AGAINST UNITED STATES AIRCRAFT 

DURING THE BATTLE FOR SAIPAN 

By 

Daniel J. Schaefer 

May 2024 

Director of Thesis: Dr. Jennifer McKinnon 

 

Major Department: Program in Maritime Studies, Department of History 

 

ABSTRACT 

This thesis endeavors to examine WWII-era Japanese radar emplacements and decipher 

the technology used during the battle for Saipan in 1944 in order to understand United States 

(US) aircraft losses. These Japanese search and fire-control radar emplacements allowed the 

detection and destruction of dozens of US aircraft through anti-aircraft fire on an unprecedented 

level. The thesis provides the first narrative of the US’s underestimation of the effectiveness of 

Japanese radar capabilities and how it relates to the location of submerged aircraft.  

This thesis primarily utilizes archival research, archaeological survey, geographic 

information system (GIS) analysis, and predictive modeling to locate Japanese radar 

emplacements and downed US aircraft. The archival research includes obtaining Japanese and 

US radar technology documentation, US Navy after-action reports, and US and Japanese maps 

and intelligence reports of Saipan’s defensive fortifications. An archaeological survey was 

conducted in Saipan at "Radar Hill," Naftan Peninsula, Mañagaha Island, and other potential 



 

 

  

locations of Japanese radar emplacements. Archeological data from the 2019-2023 East Carolina 

University/Defense POW/MIA Accounting Agency (DPAA) mission was utilized as a part of 

this research. The locations of lost US aircraft located in Tanapag Harbor and around Saipan 

were mapped, and a GIS model was created and analyzed to identify specific aircraft and any 

correlation they may have to the Japanese radar and anti-aircraft emplacements. Ultimately, this 

research attempts to predict the potential for aircraft losses in relation to radar location and range, 

thus contributing to site locations and individual site formation. Japanese radar technology is a 

severely neglected technological innovation in the historical record of the Pacific War, and 

Saipan and its archaeological signature provides a case study to examine its effectiveness. 

 

 

 

 

 

 

 

 

 

Key Words: radar, Japanese radar, WWII, anti-aircraft, aircraft, predictive modeling, GIS 



 

 

  

 

 

 

 

  



 

 

 

 

THE BEAMING SUN:  

THE EFFECTIVENESS OF IMPERIAL JAPANESE RADAR  

AGAINST UNITED STATES AIRCRAFT 

DURING THE BATTLE FOR SAIPAN 

A Thesis 

Presented to the Faculty of the Department of History  

East Carolina University 

 

In Partial Fulfillment of the Requirements of the Degree  

Master of the Arts in Maritime Studies 

By  

Daniel J. Schaefer 

May 2024 

 

Director of Thesis: Jennifer McKinnon, Ph.D. 

Thesis Committee Members: 

Nathan Richards, Ph.D. 

David Stewart, Ph.D. 

 



ii 

 

  

       

 

 

 

 

 

 

 

© Daniel J. Schaefer, 2024 

 

 

 

 

 

 

 

 

 



iii 

 

  

Dedication 

For the scouts of the 101st Airborne Division, 1st Battalion 506 Infantry Regiment, HHC, 

“Blacksheep” Reconnaissance Platoon. Their efforts sparked my interest in radio 

communications and enabled me to comprehend similar Imperial Japanese radar principles. Most 

importantly, they forged a brotherhood through sweat and fire. You guys taught me the 

importance of always being perceptive, giving it your all, and never leaving a comrade behind.  

Currahee! 

-Blacksheep-6R 

 

 

 

 

 

 

 

 

 

 

 



iv 

 

  

ACKNOWLEDGMENTS 

 

 This thesis began when I sought to uncover why there were so many US aircraft losses 

during the battle for Saipan, many of which remain submerged and unlocated around the island, 

when the mainstream historical narrative describes Japanese aircraft and anti-aircraft weaponry 

as being infamously antiquated throughout the Second World War. If this indeed was true, I 

wanted to know why so many US aircraft were lost in a supposed surprise attack during the 

battle for Saipan in 1944. I soon discovered the Imperial Japanese Navy had advanced radar 

capabilities during the Second World War and identified emplacement after emplacement on 

Saipan. So much so, that I uncovered that Saipan was the first time Imperial Japan operationally 

employed fire-control radar. This thesis is the first to examine the archaeological and historical 

evidence of the effectiveness of Japanese radar at Saipan and its relation to US aircraft wrecks. It 

is also one of the very few historical sources to analyze Imperial Japanese radar technology. 

These discoveries would not have been possible without the great assistance of many individuals. 

 Notably, these advances in adding to the historical narrative of the Second World War 

were only possible with the mentorship of my advisor, Dr. Jennifer McKinnon. Throughout this 

thesis, she provided vital guidance, support, and assistance throughout my edits, research, and 

fieldwork on Saipan. Also, many thanks to my committee members, Dr. Nathan Richards and 

Dr. David Stewart, who provided essential feedback and critiques that made this thesis possible. 

 Additional thanks to Trent Telenko, who had assisted with the technical capabilities of 

WWII radar, particularly those of the Japanese. His interest in Japanese radar and experience as 

the Quality Technical Lead in the Defense Contract Management Agency provided essential 

technical assistance for understanding Japanese radar capabilities. 



v 

 

  

 Finally, I want to give a special thanks to local guide and historian Fred Camacho, with 

whom I worked throughout this thesis. The present archeological locations of the radar 

emplacements could not have been determined without Fred’s expert navigational skills and 

local knowledge. We spent countless hours in the jungle, machete in hand, hacking away to 

locate the Japanese radar emplacements on the island. His local wartime knowledge of the island 

is unparalleled, and he is an all-around great guy and friend. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



vi 

 

  

TABLE OF CONTENTS 
 

Acknowledgments.......................................................................................................................... iv 

Table of Contents ........................................................................................................................... vi 

List of Figures ................................................................................................................................ ix 

Abbreviations .............................................................................................................................. xvii 

Chapter 1 Introduction .................................................................................................................... 1 

1.1. Brief Overview of Saipan ............................................................................................. 3 

1.3. Research Questions ....................................................................................................... 7 

1.4. Site Introduction............................................................................................................ 8 

1.5. Methodology ............................................................................................................... 11 

1.6. Justification ................................................................................................................. 13 

1.7. Limitations .................................................................................................................. 14 

Chapter 2 Background .................................................................................................................. 16 

2.1. How Does Radar Work? ............................................................................................. 16 

2.2. History of Early Radar ................................................................................................ 17 

2.3. Japanese Radar Development During WWII .............................................................. 18 

2.4. Operation Forager ....................................................................................................... 21 

Chapter 3 Methodology ................................................................................................................ 26 

3.1. Survey Methodology ................................................................................................... 26 

3.1.1. Site Survey ............................................................................................................... 26 

3.2. Archival and Historical Research ............................................................................... 29 

3.2.1. Historical Research .................................................................................................. 30 



vii 

 

  

3.2.2. Archival Research .................................................................................................... 32 

3.3. Analytical Methodology ............................................................................................. 35 

3.3.1. Japanese Radar Emplacements’ Detection Range GIS Model ................................ 35 

3.3.2. Japanese Anti-Aircraft Emplacements Fields of Fire Model ................................... 36 

3.4. Limitations .................................................................................................................. 36 

Chapter 4 History .......................................................................................................................... 40 

4.1. Japanese Radar ............................................................................................................ 40 

4.1.1. Japanese Mark 1 Model 1 Aerial Search Radar ....................................................... 40 

4.1.3. Japanese Mark 1 Model 2 Aerial Search Radar ....................................................... 42 

4.1.2. Japanese Mark 1 Model 3 Aerial and Surface-Search Radar .................................. 43 

4.1.4. Japanese Mark 4 Model 3 Fire-control Radar.......................................................... 45 

4.1.5. Japanese Mark 6 Model 4 Type 3 Airborne Search Radar ...................................... 49 

4.2. US Aircraft .................................................................................................................. 51 

4.2.1. US Grumman F6F-3 Hellcat .................................................................................... 51 

4.2.2. US Douglas SBD-5 Dauntless ................................................................................. 53 

4.2.3. US Grumman TBM and General Motors TBF Avenger ......................................... 54 

4.2.4. US Grumman FM-2 Wildcat ................................................................................... 55 

4.3. Japanese Anti-Aircraft Weaponry............................................................................... 56 

4.4. Japanese Radar at the Battle for Saipan ...................................................................... 63 

4.5. Post-Battle Japanese Radar Countermeasures ............................................................ 70 



viii 

 

  

Chapter 5 Archeological Data and Analysis ................................................................................. 78 

5.1. Radar Hill Survey ....................................................................................................... 78 

5.2. US Aircraft vs. Japanese Radar and AA ArcGIS Model ............................................ 98 

5.3. Naftan Peninsula Survey ........................................................................................... 110 

5.4. Dandan Village Survey ............................................................................................. 119 

5.5. Mañagaha Island Survey ........................................................................................... 122 

5.6. PACBAR III “Dummy” Site ..................................................................................... 127 

5.7. Tinian Radar Emplacements Surveys ....................................................................... 130 

Chapter 6 Conclusion .................................................................................................................. 137 

6.1. Historical Research Results ...................................................................................... 137 

6.2. Archaeological Research Results .............................................................................. 142 

6.3. Future Archaeological Projects ................................................................................. 144 

References ................................................................................................................................... 147 

Appendix A: US Aircraft Losses Over or Nearby Saipan .......................................................... 163 

Appendix B: Freedom of Information Act Request - DON-NAVY-2022-008745 .................... 187 

 

 

  

 

 

 

 

 



ix 

 

  

LIST OF FIGURES 

 

Figure 1. Location of Saipan and the Mariana Islands ....................................................... 5 

Figure 2. Overview 1944 map of Saipan ............................................................................ 6 

Figure 3. Radar fundamentals ........................................................................................... 17 

Figure 4. Bistatic radar fundamentals ............................................................................... 17 

Figure 5. Transmitted and received radar pulse on scope ................................................. 17 

Figure 6. Guadalcanal Mark 1 Model 1 search radar........................................................ 41 

Figure 7. Japanese Mark 1 Model 2 aerial search radar ................................................... 43 

Figure 8. Japanese Mark 1 Model 3 surface and aerial search radar ................................ 45 

Figure 9. Japanese Mark 4 Model 3 fire-control radar ..................................................... 46 

Figure 10. Japanese fire-control radar system fundamentals with AA guns .................... 47 

Figure 11. Mark 4 Model 3 fire-control Japanese radar, Nagasaki .................................. 49 

Figure 12. First captured B5N “Kate” equipped with H-6 airborne search radar off Aslito 

Airfield .............................................................................................................................. 50 

Figure 13. Captured B5N “Kate” equipped with H-6 airborne search radar painted in US 

colors for analysis ............................................................................................................. 51 

Figure 14. Airframe of F6F Hellcat (top, bottom, side).................................................... 53 

Figure 15. Airframe of Douglas SBD-5 Dauntless (bottom, front, side) .......................... 54 

Figure 16. Airframe of Grumman TBF Avenger (side, top, and front view) ................... 55 

Figure 17.  Airframe of Grumman FM-2 Wildcat (front and top view). .......................... 56 

Figure 18. Type 98 20 mm. AA gun captured on Saipan. ................................................ 57 

Figure 19. Type 96 25 mm. AA gun captured on Saipan ................................................. 58 

Figure 20. Type 88 75 mm. AA gun captured on Saipan. ................................................ 59 



x 

 

  

Figure 21. Type 10 120 mm. AA gun captured on Saipan ............................................... 60 

Figure 22. Type 2 Model 1 fire-control director or computer commonly used with medium 

and larger Japanese AA guns ............................................................................................ 61 

Figure 23. Type 3 80 mm. AA gun captured on Saipan ................................................... 62 

Figure 24. 127 mm. Type 89 dual-purpose AA and artillery gun..................................... 63 

Figure 25. Saipan Japanese Sectors of Defense ................................................................ 67 

Figure 26. Captured translated Japanese document: Radar warning regulations for air and 

surface search (5th Special Base Force), August 1943. .................................................... 68 

Figure 27. Radar operation hours and readiness levels for Naftan Peninsula and Radar 

Hill/Denshinyama emplacements ..................................................................................... 69 

Figure 28. Report stating Saipan Japanese search radar emissions from likely Naftan 

Peninsula or Radar Hill, given its operating frequency of 99.3 MHz., was detected by the 

USS Alabama on June 12-13, 1944 .................................................................................. 70 

Figure 29. Army-Navy Early Warning Radar System over mainland Japan .................... 74 

Figure 30. 1945 Japan early warning radar coverage, June 1945 ..................................... 75 

Figure 31. Japan's early warning radar coverage over the Philippines as of December 4, 

1944................................................................................................................................... 75 

Figure 32. All known Japanese early search warning search radar locations with 

georectified Section 22 Japanese radar map overlays ....................................................... 76 

Figure 33. Barrage jamming and spot jamming fundamentals diagram ........................... 76 

Figure 34. Radar Hill was the linchpin of defenses for Imperial Japan’s final line of 

resistance as of June 28, 1944 ........................................................................................... 79 



xi 

 

  

Figure 35. Radar Hill locations labeled as “strong points” in a post-battle intelligence 

report, June 28, 1944 ......................................................................................................... 80 

Figure 36. IJN compound structures noted by the author located on Radar Hill from 

intelligence report with searchlight and three heavy AA guns observed, February 1944  

........................................................................................................................................... 81 

Figure 37. Japanese radar emplacement field in relation to nearby IJN buildings ........... 81 

Figure 38. Mark 4 Model 3 fire-control radar emplacement field overlooking Tanapag 

Harbor filled with submerged downed US aircraft with local historian and guide Fred 

Camacho ........................................................................................................................... 82 

Figure 39. (Left): Potential vacuum tube located in Radar Hill field, 2015. (Right): 

Approximately 80 vacuum tubes are required for the Mark 1 Model 1 radar receiver and 

transmitter ......................................................................................................................... 83 

Figure 40. Suspected destroyed antenna, potentially Mark 1 Model 1 radar. Corroded metal 

bar approximately 30 ft. long found at the peak of Radar Hill ......................................... 83 

Figure 41. Radar Hill private property. Cemetery adjacent (circled) to Radar Hill field (red 

dot) .................................................................................................................................... 85 

Figure 42. Mark 4 Model 3 or Type 3 fire-control radar and AA battery functional diagram, 

see “Type 2 & 3 Fire Control” .......................................................................................... 85 

Figure 43. Takao City, Formosa Mark 4 Model 3 fire-control radar emplacement, believed 

to be of similar orientation to Saipan’s Radar Hill Mark 4 Model 3 fire-control radar .... 86 

Figure 44. Mark 4 Model 3 fire-control radar receiver captured on Saipan, front, July 1944

........................................................................................................................................... 87 



xii 

 

  

Figure 45. Mark 4 Model 3 fire-control radar receiver captured on Saipan, side, July 1944

........................................................................................................................................... 87 

Figure 46. Mark 4 Model 3 fire-control radar transmitter captured on Saipan, July 1944 ... 

........................................................................................................................................... 88 

Figure 47. Mark 4 Model 3 fire-control radar transmitter captured on Saipan, scope, July 

1944................................................................................................................................... 88 

Figure 48. US Marines on Radar Hill’s main road, 5 July 1944 ...................................... 89 

Figure 49. A concrete marker with an Imperial Japanese Navy anchor with a 

chrysanthemum in the center was found adjacent to the road near the radar emplacement 

location .............................................................................................................................. 89 

Figure 50. Potential Japanese Mark 4 Model 3 fire-control radar receiver module on Radar 

Hill shown on post-battle footage, 22 July 1944 .............................................................. 90 

Figure 51. Type 3 80 mm. AA gun on Radar Hill shown on post-battle footage, radar 

antenna shown in the upper right background, 22 July 1944 ........................................... 91 

Figure 52. Japanese Mark 1 Model 1 aerial search radar on Radar Hill shown on post-battle 

footage............................................................................................................................... 91 

Figure 53. Destroyed Japanese Mark 1 Model 1 aerial search radar on Radar Hill shown on 

post-battle footage, 22 July 1944. ..................................................................................... 92 

Figure 54. Destroyed Mark 1 Model 1 Japanese Search Radar ........................................ 92 

Figure 55. Wrecked Mark 1 Model 1 aerial search radar ................................................. 93 

Figure 56. Eastern entrance of “Radar Hill” command headquarters southern building .. 94 

Figure 57. Interior of “Radar Hill” command headquarters southern building, potentially 

housed IJN radar operators/technicians and IJN leadership ............................................. 94 



xiii 

 

  

Figure 58. Corner profile of Radar Hill command headquarters southern building ......... 95 

Figure 59. Japanese two-story Radar Hill headquarters, likely tank round (75 mm.) impact 

site ..................................................................................................................................... 96 

Figure 60. Japanese two-story “Radar Hill” headquarters, 2nd floor walkway ................ 97 

Figure 61. Japanese two-story “Radar Hill” headquarters maintenance room tool wall .. 97 

Figure 62. US Army occupation soldiers’ engravings inside IJN two-story headquarters ... 

........................................................................................................................................... 98 

Figure 63. Saipan Japanese radar emplacement range .................................................... 100 

Figure 64. Captured Japanese document on the principal sky watch areas or fields of fire 

for each AA unit at Saipan .............................................................................................. 101 

Figure 65. Saipan Japanese AA unit fields of fire fields ArcGIS model from captured 

Japanese AA principal sky watch areas document, highest concentration of fire shown in 

Tanapag Harbor .............................................................................................................. 102 

Figure 66. All located US aircraft are located adjacent to the highest concentration of 

Japanese AA. Shown east is the suspected Japanese Mark 4 Model 3 fire-control radar that 

enabled the destruction of those aircraft ......................................................................... 103 

Figure 67. Launch coordinates of aircraft carrier USS Lexington with fleet on 11 June 1944 

at 1300 after being compromised, noted with red rectangle ........................................... 104 

Figure 68. 11 June 1944 aircraft carrier approximate launch point at 13.7° latitude 148.2° 

longitude 305 km. from Saipan compared to Japanese Mark 1 Model 3 search radar that 

detected US Mark III IFF systems up to 300 km ............................................................ 104 

Figure 69. Archeological remains of TBM Avenger with landing gear up, located in 

Tanapag Harbor downed by Japanese AA in June 1944, July 2018 ............................... 105 



xiv 

 

  

Figure 70. Diagram of archeological remains of TBM Avenger located in Tanapag Harbor 

downed by Japanese AA in June 1944, July 2018 .......................................................... 106 

Figure 71. F6F-3 Hellcat downed by Japanese AA in Tanapag Harbor. Engine (indicated 

by red square), landing strut and tire (indicated by yellow square), and .50-caliber gun 

(indicated by white arrow); 30 cm. scale, view looking north........................................ 106 

Figure 72. Radar Hill Mark 4 Model 3 emplacement field from Tanapag Harbor nearby 

submerged F6F Hellcat site, circled by author ............................................................... 107 

Figure 73. Survey potential for MIA US aircraft in highest Japanese AA overlap and 

adjacent areas on and beyond coral reef ......................................................................... 108 

Figure 74. May 1944 Saipan US Intelligence map with Japanese radar emplacement plotted 

on Naftan Peninsula ........................................................................................................ 111 

Figure 75. Naftan Peninsula Japanese radar emplacement with key features and anti-

aircraft emplacements plotted ......................................................................................... 112 

Figure 76. HPO 1996 survey of Naftan Peninsula Japanese radar emplacement Plan, Site 

SP5-0639, Feature 4-6 .................................................................................................... 112 

Figure 77. Naftan Peninsula Japanese radar tower, May 2023 ....................................... 114 

Figure 78. Naftan Peninsula Japanese radar tower with Mark 1 Model 1 radar sketch, May 

2023................................................................................................................................. 114 

Figure 79. Naftan Peninsula Japanese radar tower antenna mount from top, May 2023 

......................................................................................................................................... 115 

Figure 80. Footage of destroyed Model 1 Mark 1 aerial search, Saipan 1944, Naftan 

Peninsula ......................................................................................................................... 115 

Figure 81. Empty 127 mm. AA gun emplacement in Naftan Peninsula radar footage .. 116 



xv 

 

  

Figure 82. Naftan Peninsula radar emplacement building underground cable port with 

wires ................................................................................................................................ 117 

Figure 83. White rubber insulation cable from power supply unit to a communications 

transmitter ....................................................................................................................... 117 

Figure 84. Three 127 mm. AA guns were observed near the Naftan Peninsula radar 

emplacement ................................................................................................................... 118 

Figure 85. Type Mark 1 Model 3 Japanese search radar, Saipan 1944, 1300 yds. north of 

the eastern end of Aslito Airfield 1945 ........................................................................... 120 

Figure 86. US Intelligence report on Mark 1 Model 3 Japanese search radar, Saipan 1944, 

1300 yds. north of the eastern end of Aslito Airfield ..................................................... 120 

Figure 87. Approximate location of Mark 1 Model 3 radar emplacement from US aerial 

reconnaissance photo, 22 February 1944 ........................................................................ 121 

Figure 88. Suspected present location of Mark 1 Model 3 Japanese search radar, Saipan 

1944, 1,300 yds. north of the eastern end of Aslito (now Isley) Airfield ....................... 122 

Figure 89. Intelligence report of Garapan Town and Tanapag Harbor, 15 May 1944 ... 123 

Figure 90. Japanese sound locator, predecessor of radar, reported located on eastern 

Mañagaha in intelligence report of Garapan Town and Tanapag Harbor ...................... 124 

Figure 91. Whale 1943 war patrol in Patrol Area 14 in the Marianas Islands ................ 125 

Figure 92. Four Type 96 AA guns and a suspected antenna mast are submerged in the 

eroded eastern half of Mañagaha Island ......................................................................... 126 

Figure 93. Submerged Type 96 AA located in the eroded eastern half of Mañagaha Island, 

May 2023 ........................................................................................................................ 127 



xvi 

 

  

Figure 94. Submerged suspected antenna mast located in the eroded eastern half of 

Mañagaha Island, May 2023 ........................................................................................... 127 

Figure 95. 1-24 Marines line of departure where they reported the “dummy” radar 

emplacement ................................................................................................................... 128 

Figure 96. Japanese “Dummy” radar emplacement, modeled after Mark 1 Model 1 search 

radar, located on Mt. Petosukura, located near the present PACBAR III radar installation

......................................................................................................................................... 129 

Figure 97. Present “dummy” Japanese radar emplacement location near PACBAR radar 

compound, concrete “antenna” base located by Fred Camacho ..................................... 130 

Figure 98. Two Japanese radar emplacements reported on Tinian in US intelligence report

......................................................................................................................................... 131 

Figure 99. Tinian Japanese radar emplacements ............................................................ 132 

Figure 100. Destroyed Mark 1 Model 2 aerial search radar located off the northern Tinian 

airfield from post-battle intelligence report .................................................................... 133 

Figure 101. Destroyed Mark 1 Model 1 radar on Tinian ................................................ 134 

Figure 102. Destroyed Mark 1 Model 1 radar on Tinian from post-battle intelligence report

......................................................................................................................................... 135 

Figure 103. Photographs of destroyed Mark 1 Model 1 radar on Tinian ....................... 136 

 

 

 

 

 

 



xvii 

 

  

ABBREVIATIONS 

 

AA Anti-Aircraft 

AAA Anti-Aircraft Artillery 

AAR After Action Report 

CIA Central Intelligence Agency 

CNMI Commonwealth of the Northern Mariana Islands 

DPAA Defense POW/MIA Accounting Agency 

FOIA Freedom of Information Act 

GIS Geographic Information System  

HPO Historic Preservation Office 

IFF Identify Friendly or Foe 

IJN Imperial Japanese Navy 

IJA Imperial Japanese Army 

MIA Missing in Action 

NARA National Archives and Records Administration 

NRL Naval Research Laboratory 

PACBAR Pacific Barrier Radar 

SBD Scout Bomber Douglas 

SCR Set, Complete, Radio 

SLC Search Light Control 

TBF Torpedo Bomber Grumman 

TBM Torpedo Bomber General Motors 

USS United States Ship 

VHF Very High Frequency 

UXO Unexploded Ordnance 

VP Patrol Squadron



 

163 

CHAPTER 1 INTRODUCTION 

The archeological analysis of Japanese radar capabilities and their effectiveness is an 

understudied topic. Historically, the effectiveness of Japanese radar is often ignored due to 

preconceived notions that the US had an overwhelming and complete industrial and intellectual 

monopoly over Japan before and during WWII (Macdonald 2021; Hallas 2019; Galati 2015; 

Peatie 2015). WWII studies and post-war battle narratives of the battle for Saipan have neglected 

to address and analyze Japanese radar technology development and effectiveness during the war. 

The small island of Saipan, along with the other Mariana Islands in the western Pacific, acted as 

the lynchpin of the defensive network that protected the mainland territory of Imperial Japan 

from US attack and invasion. Japanese radar technology was critical for the island’s defense. As 

such, the battle for Saipan provides an excellent case study for analyzing Japanese radar 

capabilities. It was the first island the US invasion force encountered with comprehensive radar 

coverage through multiple search radar and fire-control radar emplacements. From the initial 

moments of the battle, Japanese search radar detected the US invasion fleet on 11 June 1944 

(Stafford 1962:167). Additionally, an abnormally accurate and heavy anti-aircraft (AA) fire was 

reported in US aviators’ after-action reports (AARs) during the battle. Interestingly, a surviving 

Japanese Mark 4 Model 3 fire-control radar was captured during the battle and was shipped to 

the Naval Research Laboratory (NRL) in Washington, DC, to develop countermeasures and 

jamming capabilities, demonstrating the success of its capabilities (Bonham and Lonsdale 1945). 

Still, the cause of these Japanese radar successes was never explained, even though the Japanese 

anti-aircraft fire was infamous for its inaccuracies (USS Lexington 1944a).  

The chapters of this thesis on the effectiveness of Japanese radar during the battle for 

Saipan are organized, and Chapter 1 provides an introduction and overview of Saipan. This 

 



 

2 

 

chapter presents the thesis research questions on Japanese radar. Additionally, the chapter 

provides site introductions of the Japanese radar emplacements with the intended methods, 

justification for the research, and potential limitations. Chapter 2 provides further background 

knowledge on the specifics of radar and how it works. Special attention is given in this chapter to 

the history of the research and development of Imperial Japanese radar and a background on the 

battle for Saipan. Chapter 3 details the methods utilized in this thesis and details how survey 

fieldwork was conducted. This chapter further describes the extensive historical and archival 

research conducted. Lastly, the chapter describes the analytical methodology conducted, 

primarily through an ArcGIS fields of fire model relating Japanese radar emplacements to 

downed US aircraft locations. Chapter 4 describes the history and capabilities of Japanese radar 

and the types of search, fire-control, and airborne radar systems believed to have been used in the 

Saipan theater of operations. The history and capabilities of the types of US aircraft downed 

during the battle are also detailed. The history and capabilities of Japanese anti-aircraft weaponry 

utilized with radar to down these aircraft are also described, as well as the history of US military 

electromagnetic radar countermeasures and capabilities of Japanese radar. Chapter 5 analyzes the 

archaeological data collected from the survey site locations. Notably, it analyzes the data from 

the created ArcGIS fields of fire model representing Japanese AA's highest concentration fields 

of fire that partnered with radar and the concentration’s relationship to downed US aircraft 

locations. Lastly, Chapter 6 acts as the conclusion of the thesis, where the historical and 

archeological research results are discussed, as well as the potential for future research. 

This thesis proposes that the accuracy of Japanese radar enabled the downing of dozens 

of US aircraft, having precisely and quickly locked in on their location. It also proposes that the 

ranges of the radar emplacements and the related fields of fire of Japanese anti-aircraft 



 

3 

 

emplacements can be predictive in locating additional downed US aircraft from the battle. The 

thesis research contributes to understanding the overall usage of Japanese radar during the 

Second World War and specifically during the battle for Saipan. The intellectual depreciation of 

the US towards the Japanese and their technological capabilities in radar ultimately cost the lives 

of dozens of airmen at Saipan and thousands of airmen throughout the war. Japanese radar 

detected a US invasion fleet through search radars and often gave over an hour of warning to the 

defender’s aircraft and anti-aircraft emplacements. These search radars would lock in on US 

aircraft, knowing their numbers, azimuth, and altitude well before reaching an island from their 

aircraft carriers (Nakagawa 1997:44). Via radar, the Japanese could direct dozens of their anti-

aircraft emplacements through radio communication and fire-control directors to focus all fire 

accurately and heavily towards one specific aircraft or aircraft formation. Saipan was the first 

time these comprehensive layers of radar coverage were used in Japanese defenses. Thus, it acts 

as the perfect case study on its effectiveness. Through their industrial capabilities and widely 

published technological innovations, the superiority complex of the US victors obscured most of 

the propagated innovation of the Japanese during the Second World War. An example of this 

obscurity can be seen in Japanese radar technology being concealed by US military leadership to 

cover early significant inefficiencies in their own radar technology. 

1.1. BRIEF OVERVIEW OF SAIPAN 

           Saipan is an island in the western Pacific Ocean of the Mariana Islands chain (Figure 1). It 

is approximately 14 mi. long and 5 mi. wide, with approximately 45 sq. mi. in landmass (Figure 

2). Human settlement goes back 4,000 years, eventually becoming permanent with the native 

Chamorro population. The island was first encountered and recorded by Europeans in 1521 by 

Spanish explorer Ferdinand Magellan. The Spanish officially settled on the island in 1668, 



 

4 

 

adding the island to their imperial dominion. They occupied Saipan until 1898 when the island 

was sold to Germany following Spain’s defeat during the Spanish-American War. Following 

World War One and Germany’s defeat, the occupied land was ceded to Japan in 1919. The 

island’s infrastructure expanded exponentially through Japanese occupation to support the 

economically fruitful sugar cane industry. Throughout the 1930s, Imperial Japan also began 

building up the island’s defenses (Hoffman 1950:2-3). This construction effort led to Saipan 

becoming the lynchpin of Imperial Japan’s defenses during World War Two. Saipan’s defenses 

faced and eventually fell to a US amphibious invasion and battle lasting from 11 June 1944 to 9 

July 1944. Following the island’s capture, the US occupied Saipan, and it became a trust territory 

following the war. In 1978, the Northern Mariana Islands became a Commonwealth of the US, 

and Saipan became the capital of the Commonwealth of the Northern Mariana Islands along with 

the remainder of the island chain sans Guam. 



 

5 

 

 

Figure 1. Location of Saipan and the Mariana Islands (Hoffman 1950:3). 



 

6 

 

 

Figure 2. Overview 1944 map of Saipan (Hoffman 1950:5). 

 

  



 

7 

 

1.3. RESEARCH QUESTIONS 

The primary question explored in this research is “What was the effectiveness of 

Japanese radar technology and emplacements used at Saipan, and how did that impact the record 

of losses and locations of US aircraft?” The geographical terrain of the Japanese radar 

emplacements was analyzed to determine the tactical significance of the location. Additionally, 

considerations of elevation and line of sight were confirmed through archival sources and 

archaeological survey, as these are essential for precise radar detection and facilitation of radio 

wave communication between the radar emplacements and their command of anti-aircraft 

installations.  

The thesis plots all known US aircraft downed by Japanese anti-aircraft fire through 

Japanese radar emplacements using a geographic information systems (GIS) platform. This was 

conducted to determine if and how the Japanese radar emplacements on Saipan detected and 

destroyed US aircraft. Archaeological surveys were conducted on the Japanese radar 

emplacements, related Imperial Japanese Navy (IJN) structures, and specific US aircraft wrecks, 

particularly those downed in Tanapag Harbor. An attempt was made to determine the cause of 

the downed aircraft through anti-aircraft fire to confirm the US Naval after-action reports of 

unusually “heavy and accurate” fire from Japanese anti-aircraft emplacements on Saipan 

(USS Lexington 1944a).  

To accomplish these goals, the following questions were considered during research: 

 

1. Where are the Japanese search and fire-control radar emplacements located on Saipan, 

and why did the Japanese choose the locations? 



 

8 

 

2. How does the location of the Japanese radar emplacements relate to the location and site 

formation of downed US aircraft around Saipan?  

3. Why did US forces underestimate Japanese radar technology and were unaware of their 

fire-control radar use? 

4. Why did US aircraft attack Tanapag Harbor, given its heavy Japanese anti-aircraft 

emplacements rather than naval bombardment? 

5. How did the Japanese detect the US invasion fleet off Saipan? Why were the Japanese 

aircraft not scrambled at Aslito Airfield? 

6. Can a predictive model for Japanese anti-aircraft fields of fire determine where additional 

downed US aircraft are located? 

1.4. SITE INTRODUCTION 

Saipan was the site of Operation Forager from 11 June to 9 July 1944, where the US 

broke off Imperial Japan’s final defensive perimeter that protected its mainland islands. US 

aircraft victims of the Japanese radar emplacements located on Saipan have been identified since 

the initial fieldwork of the side scan sonar and magnetometer survey of Tanapag Harbor in 2008 

(Burns 2008). East Carolina University conducted fieldwork focusing specifically on target 

testing in the harbor in 2018, where a Grumman F6F-Hellcat was identified, and a 

Grumman TBM-Avenger was reassessed in 2018. The propeller of another Grumman F6F-

Hellcat was also believed to have been located (McKinnon 2019). The Japanese radar 

emplacement locations on Saipan were initially determined through recovered archival data and 

local oral histories, where further archeological survey could be conducted. This thesis examines 

four potential Japanese radar emplacements on the island of Saipan. Those radar emplacements 

were believed to have been located on “Radar Hill,” Naftan Peninsula, Dandan Village, Mount 



 

9 

 

Petosukara, and nearby Tinian if physically feasible. The Japanese radar emplacement locations 

had been forgotten since 1945 and had never been deliberately recorded before this thesis.  

The primary and heavily vegetated archaeological site goes by many names that still 

harken back to its past as a communications epicenter, such as “Radar Hill,” and today it is still 

known as Wireless Ridge. The Chamorro name for the site is Talofofo, or "between bubbling 

springs" (Fred Camacho March 2022 pers comm.). Local informants and historians were 

unaware of the significance of Japanese radar emplacements on Saipan. Local historian and 

expert guide Fred Camacho was also previously unaware of the several Japanese buildings 

located there, which are the most complete he had ever seen, particularly of structures located in 

the center of the island. 

On Radar Hill, these Japanese structures that likely were used as the IJN command 

apparatus for the defense and operation/maintenance of the area's many radar and 

communication apparatuses were examined. Captured Japanese radar documents confirm the 

existence of a Japanese radar emplacement having been located there. The peak of “Radar Hill,” 

with a clear line of sight of the west and east approaches of the island, was additionally examined 

as this location would have offered an optimal line of sight of the Mark 1 Model 1 search radar 

(Naval Research Laboratory 1943). 

Offshore of Saipan, Mañagaha Island was believed to be the location of a Japanese radar 

emplacement where US submarines scouted out Japanese radar in 1944 (Lotz 2018:128). The 

most notable archaeological remains reported on the island are located on the eastern face, where 

multiple Japanese anti-aircraft emplacements remain submerged as the island has heavily eroded 

in the decades following the battle. The site was repeatedly archivally observed as a Japanese 



 

10 

 

radar emplacement site and would have been ideal given Mañagaha Island’s guarding nature of 

the harbor.  

Naftan Peninsula is a densely forested jungle peninsula located on the southernmost 

portion of the island. Captured Japanese radar documents and intelligence gained from aerial 

reconnaissance confirm the existence of a Japanese search radar emplacement having been 

located there. The archeological remains along the Naftan Peninsula are substantial, and the area 

has remained relatively untouched since the battle. The jungle of the Naftan Peninsula is 

exceptionally dense, and wartime structures are obscured. It was believed that this would be true 

with the Japanese radar emplacement located there.  

Dandan Village is located on the eastern end of Aslito Airfield, where US intelligence 

recorded a Mark 1 Model 3 search radar emplacement. Through intelligence photographs, the 

emplacement appeared to have walls constructed of wood and a roof of tin with a camouflaged 

Mark 1 Model 3 antenna mast. The emplacement was recorded 1,300 yds. north of the eastern 

end of Aslito Airfield and presently would be located in the built-up area of Dandan Village.  

Notice was additionally given to a “dummy” radar emplacement, recorded in battle 

archival intelligence reports, located in the northern portion of the island on Mount Petosukura 

near the PACBAR (Pacific Barrier) III Cold War radar emplacement. Although not logistically 

physically possible for survey during this thesis research, Tinian Japanese radar emplacements 

were also located on Mount Lasso and off the northern Japanese airfield. Military intelligence 

reports reported an additional radar emplacement in the south of Tinian. Travel blogger Howard 

Cole had previously located the radar emplacement on Mount Lasso, but it has never been 

officially archaeologically surveyed (https://hiketinian.blogspot.com/2008/02/tinians-japanese-



 

11 

 

radar.html). There is much additional future survey potential for Japanese radar emplacements on 

the island of Tinian. 

1.5. METHODOLOGY 

The 2008 side scan sonar and magnetometer survey of Tanapag and Garapan Lagoons 

and the fieldwork since that time, specifically from 2018, have defined some US aircraft 

locations downed by anti-aircraft fire and enabled through Japanese radar (Burns 2008, 

McKinnon 2019). Some types of submerged US aircraft were established, and the potential 

identification of any possible recovered remains of the aviators flying the aircraft is underway 

through a partnership between ECU and the Defense POW/MIA Accounting Agency (DPAA). 

Attempts were made from collected data to confirm the cause of the aircraft downing using a 

GIS framework and show the relationship of the aircraft’s destruction to the location of the 

Japanese radar emplacements and their detection range. Additional attempts were made to 

establish through GIS that the invasion fleet was detected through Japanese radar on 11 June 

1944. 

Comparative analyses of US aircraft anti-aircraft fire losses were established to 

understand the efficiency of Japanese anti-aircraft fire at Saipan. All the downed aircraft were 

plotted through GIS modeling with their location (or approximate if MIA) and cause of 

destruction noted. The aircraft downing locations towards the Mark 4 Model 3 fire-control radar 

are expected to be higher the closer in distance they are to the radar emplacements. The location 

of Japanese radar sites and their efficiency at Saipan was attempted to be determined primarily 

through US intelligence reports at various archival sources and through Freedom of Information 

Act (FOIA) requests.  



 

12 

 

ArcGIS will be utilized to create predictive modeling for downed US aircraft around 

Saipan from the fields of fire of Japanese anti-aircraft guns and ranges of radar emplacements. 

Through the predictive modeling, it is expected where the fields of fire of the anti-aircraft guns 

overlap are the locations that would be likely sites of downed US aircraft, as Japanese flak was 

the heaviest in those locations. Remote sensing methodologies can then be used on those more 

site-specific locations to facilitate the attempt to locate some of the dozens of missing-in-action 

US aircraft. 

Archeological surveys were conducted on the believed Japanese radar emplacement 

locations at Radar Hill, Mañagaha Island, Naftan Peninsula, and Dandan Village. Additional 

survey potential exists for the Tinian radar emplacements, as they were within Saipan’s 

airspace's detection range.  

Before further fieldwork was established, comprehensive historical and archival research 

was conducted. This thesis extensively examined archival wartime maps and documents to locate 

the radar emplacements and their capabilities. Also examined were maps from Saipan's Historic 

Preservation Office, which contains a partial record of recorded concrete structures likely from 

the Japanese occupation and battle.  

The examination of technical reports of the captured Japanese radar sets from the Naval 

Research Laboratory in Washington, DC, were heavily considered. A research focus was also 

given to the captured translated Japanese radar documents from Kwajalein Atoll in January 1944 

(Price 1984:143). Japanese documentation related to their radar capabilities, particularly at 

Saipan, was analyzed through US Naval Intelligence technical reports. There was also attempted 

research cooperation with the Japanese Military Radio Museum in Yokohama, Japan, which 

contains an operational power supply and transmitter unit of the Mark 4 Model 3 fire-control 



 

13 

 

radar like the one likely captured on Radar Hill. The museum also has a Mark 1 Model 3 

transmitter and power supply units identical to those likely utilized in Mañagaha and Dandan 

Village. Technical assistance on the capabilities of Japanese radar was through discussions with 

retired Quality Technical Lead in the Defense Contract Management Agency, Trent Telenko. 

Archaeological evidence at the Japanese radar emplacement sites was photographed and 

mapped, with models created through ArcGIS. Further land surveys were established, focusing 

on Radar Hill and Naftan Peninsula, to locate the exact location of the Japanese radar 

emplacements in 1944. Special consideration was given to attempting to locate electrical 

component artifacts. There is likely not much of the radar components remaining unless they 

were severely damaged, as most components were scrapped or disassembled and sent to the 

Naval Research Laboratory in 1944. Further research needs to be established on what happened 

to the Mark 4 Model 3 fire-control radar following the war.  

1.6. JUSTIFICATION 

  The examination of Japanese radar capabilities through a historical lens has been 

analyzed from a minimal perspective. It has been neglected through US wartime biases against 

the industrial and intellectual capabilities of the Japanese Empire. All observed recently 

published narratives related to the battle for Saipan continue that bias and neglect that the 

Japanese defenders utilized radar technology on the island. Meanwhile, the effective use of 

Japanese radar at Saipan can be uncovered through analysis of US Naval after-action reports that 

reported "heavy and accurate" anti-aircraft fire when Japanese anti-aircraft fire was known for its 

inaccurate nature (USS Lexington 1944a). Saipan suddenly sustained one of the most significant 

US battle losses through Japanese anti-aircraft fire at this point in the war. Additionally, how the 

invasion fleet was compromised has never been explained in any narrative of the battle for 



 

14 

 

Saipan. This thesis attempts to prove that the Japanese radar detected the invasion fleet on 11 

June 1944. This will also assist in the location of additional downed US aircraft using 

overlapping fields of fire of Japanese anti-aircraft fire. It is suspected that additional aircraft will 

be located near the highest concentration of AA fire.  

1.7. LIMITATIONS 

Perhaps the most significant limitation of the research was the lack of comprehensive 

secondary publication on Japanese radar. The only exception is Japanese Radar and Related 

Weapons (1997) by Yasuzo Nakagawa, which is 82 pages long and focuses on the pre-war story 

of Japanese radar technology. As such, a focus on wartime after-action and US Naval 

Intelligence reports was undertaken. 

The most apparent limitations of this thesis were cost and time. Since the survey is not 

directly related to the government-funded work of DPAA and MIA (Missing in Action) 

recovery, various grants were thought to be required for further fieldwork. Costs would include 

flights, housing, permits, and additional personnel to survey the locations on “Radar Hill,” 

Mañagaha Island, and Naftan Peninsula. Due to the potential cost and limited time, surveying 

each Japanese radar emplacement was limited in duration. 

The issue of management and ownership plays heavily into this thesis. Through an initial 

survey of Saipan’s Radar Hill, command structures associated with the maintenance and 

operation of radar emplacements were believed to have been located there. It is believed these 

structures are some of the most complete standing Japanese buildings located in the center of the 

island (Fred Camacho March 2022, pers. comm.). These resources are currently on private 

property, with the owners previously unaware of their significance. The landowners have asked 

that the sites' specific coordinates not be brought to public knowledge. Yet, public knowledge of 



 

15 

 

these sites' importance would help further the cultural value for locals, tourists, and historians, 

helping completely change the standard narrative of the battle for Saipan and the significant role 

that Japanese radar played in it.  

  



 

16 

 

CHAPTER 2 BACKGROUND 

 

2.1. HOW DOES RADAR WORK? 

Radar comes from a 1940 US Navy acronym for the technology, which means Radio 

Detection and Ranging. Radar works through transmitted pulses of radio wave energy sent out to 

travel along a straight-line path or beam. When the pulse hits an object that radio waves cannot 

penetrate, the waves are reflected and bounced back to the receiving element of the radar module 

(Figure 3). Radar operates in a monostatic function where the transmitter and receiver are in one 

location or in a bistatic function where the transmitter and receiver are in separate locations 

(Figure 4). A monostatic radar has the benefits of simplified operation, with the transmitter and 

receiver being in the same location. In contrast, bistatic radar often overcomes geographical 

blind spots, interference, and jamming. A radar operator can then deduce the object's azimuth, 

distance, and speed through an oscilloscope (Figure 5). Distinct types of radar modules are 

enabled for various roles, but through a military lens, they are primarily utilized through three 

roles. The first role is an early warning aerial search radar to locate enemy aircraft for early 

detection. The second is a surface search radar, most commonly used to detect enemy forces 

where the radar transmitter and receiver are oriented to the earth's surface. It is most used in a 

maritime role as the sea is accessible from most foliage and terrain obstructions, and enemy ships 

and surfaced submarines can easily be detected. The third role of radar through a military lens 

would be fire-control, which radar can be enabled to automatically lock in and track enemy aerial 

targets and automatically relay this information to anti-aircraft gun emplacements to destroy the 

enemy aircraft.  

 

  

 



 

17 

 

 

Figure 3. Radar fundamentals (Skolnik 2023). 

 

Figure 4. Bistatic radar fundamentals (RF Wireless World 2012). 

 

Figure 5. Transmitted and received radar pulse on scope (Sub-Committee of the Joint Committee on New Weapons and 

Equipment 1943:109). 

 

2.2. HISTORY OF EARLY RADAR 



 

18 

 

Japanese radar usage during WWII is one of the most neglected technological subjects by 

historians of the Second World War (Nakagawa 1998). Most of the public and even many 

historians are unaware that the Japanese even had radar capabilities during the war, while the few 

that are aware typically view Japanese radar as being primitive and several years behind Allied 

radar technologies (Peattie and Evans 2015:411-413). The study of radar technology in the 

Pacific Theater is often an afterthought, if any at all. For the Second World War, historians 

generally focus on the early radar of Chain Home in 1940 during the Battle of Britain, which 

saved the island by detecting and warning of wave after wave of incoming German aircraft 

(Swords 1986:131-35). Meanwhile, the Japanese were developing their advances in radar 

technology, so much so that in 1939, Japan was considered by some the most advanced in radar 

technology research and development (Galati 2015:74-76). 

Throughout the 1930s, the Japanese Empire fully embraced technological innovation in a 

laboratory setting. Even in the early 1930s, Japan considered radar a viable technical prospect to 

further their war machine. The need for early detection of US aircraft and naval forces to defend 

the ever-growing Japanese colonial empire was what propagated innovation (Nakagawa 1997:6). 

In the 1930s, the Japanese were far more technically advanced beyond the radar capabilities of 

the US, Great Britain, and Germany in most theoretical approaches (Galati 2015:76). The 

Japanese name for radar was Denpa Tanshingi, which meant “Radio Wave Probe.” They were so 

advanced in radar that they were the first to develop the cavity magnetron in 1939 (Nakajima 

1992:12). The cavity magnetron operated by utilizing microwave technology in radar, allowing 

extraordinarily accurate and rapid detection rather than through the standard long-wave radio 

wavelengths that other nations had uniformly used during this time (Nakagawa 1997:15-17). 

2.3. JAPANESE RADAR DEVELOPMENT DURING WWII 



 

19 

 

As the war expanded against the US after the attack on Pearl Harbor on 7 December 

1941, most laboratory innovations related to the war effort were initially sidelined. Japan drafted 

most of its highly trained and specialized technicians into the military, halting their significant 

technological head start over the Allies (Nakagawa 1997:42-43). Additionally, there was little 

cooperation between the Imperial Japanese Navy (IJN) and the Imperial Japanese Army (IJA) in 

competing sectors of radar research and development (Nakagawa 1997:47-48). However, the IJN 

and IJA both fully understood the essential need for radar. The observed effectiveness of Allied 

radar modules of the Signal Corps Radio (SCR)-268 fire-control radar and the Signal Corps 

Radio (SCR)-270 search radar achieved this realization (Nakagawa 1997:34). Both modules 

were designed by the US in 1940 and captured by the Japanese in 1942 at Corregidor, 

Philippines. US research and development in land-based fire-control radar would stagnate, 

mainly through the SCR-268 radar, as it would only be replaced in late 1944 (Henney 1945:103). 

Meanwhile, its capture reinvigorated Japanese radar development, bringing it out of the labs and 

into mass production with a more advanced model of their own (Nakagawa 1997:34). 

In 1941, the Japanese rapidly brought their technology into total industrial production 

after discovering how effective radar technology was for the US (Nakagawa 1997:43). The 

Japanese radar technology found by US forces during their first significant land engagement 

came as a complete shock. US intelligence had yet to consider that the Japanese were utilizing 

radar technologies, vastly believing that the Japanese were not capable of practically fielding 

their own technological innovation through the industrial and intellectual superiority complex of 

the US at that time (Grunden 2005:272). At the Guadalcanal, Solomon Islands airfield, the US 

Marines captured a Mark 1 Model 1 IJN land-based detection radar (Naval Research Laboratory 

1943). Shocked intelligence analysts shipped the radar module to the Naval Research Laboratory 



 

20 

 

in Washington, DC, for analysis. It was determined to be nearly identical to the SCR-270, as 

Japan copied it from the radar module captured the previous year from Corregidor. 

This surprising discovery prompted US intelligence to examine the full capabilities of the 

Japanese Mark 1 Model 1 radar potential. They determined that the operational frequencies of 

the captured SCR-270 and the Japanese Mark 1 Model 1 radar were in an identical range of 104-

112 MHz. (Nakagawa 1997:86). US aircraft and submarines installed radar detection and 

receiver units to monitor the frequency range and locate additional Japanese radar emplacements 

like the one found at Guadalcanal (Lotz 2018:21). In March 1943, the mission of the first 

graduating class of the Army Electronic Warfare School was to detect a Japanese Mark 1 Model 

1 radar on Kiska on a B-24 Liberator flown over Japanese-occupied terrain in the Aleutian 

Islands (Price 1984:53-55). The aircraft’s analytical systems could determine the radar 

emplacement’s location through its operating frequency range, pulse width, pulse repetition rate, 

and area coverage (Price 1984:277-79). Through radar detection units located on US aircraft and 

submarines, the US found dozens of similar Japanese radar emplacements throughout the Pacific 

region (Lotz 2018:21). The effectiveness of this electronic warfare campaign caused Japanese 

radar emplacements for a time, particularly on naval vessels, to turn off their emitters to avoid 

detection (Nakagawa 1997:49-50). In 1943, the only type of Japanese radar identified by US 

intelligence was the Mark 1 Model 1, but through concealed Japanese research and development, 

their radar technology was rapidly evolving behind the scenes (Price 1984:137).  

These newfound discoveries of masses of Japanese radar led to further reconnaissance 

efforts to locate and identify Japanese radar emplacements throughout the Pacific. The US 

submarines Greenling and Whale of Patrol Area 14 detected three Japanese radar emplacements 

in Saipan starting on 8 March 1943 (Lotz 2018:198). Initially, a periscope detected the 



 

21 

 

emplacements rather than the use of electronic warfare methodologies. Even if the submarines 

were utilizing electronic warfare, they would not have been able to detect many of the newly 

designed Japanese radar emplacements on Saipan, as they were among the most advanced 

Imperial Japan had developed under different operating frequencies. Through visual surveillance, 

the submarines confirmed the location of Japanese radar off the western cliffs of Naftan 

Peninsula, the eastern approach of Mañagaha Island, and notably at the center of the island in the 

mountains (Lotz 2018:91). It was assumed that all radar modules found on Saipan were identical 

to Guadalcanal’s radar, but they were mistaken (Price 1984:137). 

A pivot in signal intelligence was made in January 1944 with the capture of Kwajalein 

Atoll. Japanese documents captured on the island revealed the existence of multiple modules of 

Japanese radar. Most significantly, the documents confirmed the existence of the Mark 2 Model 

2 Japanese ship-borne radar that operated on precise microwave frequencies (Price 1984:143). 

These new developments should have been more adequately considered, but again, the US 

sidelined them for other intelligence considerations that were deemed more important.  

2.4. OPERATION FORAGER 

Task Force 58 was the US Naval Fleet assigned to attack the center of Imperial Japan’s 

Pacific empire (Macdonald 2021:186-89). The fleet comprised an array of 17 aircraft carriers, six 

battleships, 13 cruisers, 58 destroyers, and 1,100 aircraft (Macdonald 2021:235). This display of 

firepower gave the invading US forces of Saipan an overwhelming sense of superiority over their 

Japanese enemy. Morale was high as US aircraft had bested Japanese defenses at Truk Lagoon in 

February 1944 against the severely inaccurate Japanese anti-aircraft fire, resulting in almost no 

US aerial casualties (Stewart 1985:107). Task Force 58 had decimated the heavily fortified 



 

22 

 

harbor of Truk, and this success gave the US forces much overconfidence in their attack on 

Saipan less than four months later.  

Meanwhile, Saipan fortified itself into a defensive bastion for the Japanese Empire as the 

command headquarters for the IJN and the anchor point for “Operation Z” of Japan’s final 

intended defensive perimeter (Hallas 2019:41). General Yoshitsugu Saitō commanded the IJA 

and the IJN was led by Admiral Chūichi Nagumo, who had been sidelined to an administrative 

post after his failure at the Battle of Midway (Hallas 2019:20). Being the location of the IJN 

headquarters, it would have been afforded all the premier technology of the Japanese Empire, 

including the available Japanese radar technology and their most capable radar operators.  

When the fleet of Task Force 58 arrived off the coast of Saipan on 11 June 1944, 

Japanese radar on the island had the fleet locked in through their radar systems long before they 

arrived and were prepared for the US attack (Macdonald 2021:235-237). The US fleet arrived off 

Saipan’s eastern approach from the Marshall Islands, where the first arriving action of 225 US 

aircraft was to weaken the Japanese defenses through aerial bombardment 

(USS Lexington 1944a). Naval aviator and historian Edward P. Stafford described the initial 

attack on 11 June 1944 as, "To avoid enemy radar, the fighter sweep stayed low. Then thirty 

minutes from the target, planes assigned to high cover began their climb; twenty-five minutes 

out, intermediate cover started up and twenty minutes out, low cover..." and "despite the 

precautions, radar had warned the Japanese" (Stafford 1962:167). The Japanese were not able to 

scramble all their aircraft as they had almost all been parked and degassed to prevent an 

explosion during a US air raid. Approximately 40 aircraft got in the air and approximately 60 

aircraft were destroyed on Aslito Airfield, with nearly all being lost. Their sacrifice though 

provided Japanese AA emplacements ample opportunity to zero in on US aircraft. After the 



 

23 

 

initial June 11th attack, the radar emplacements would have been on priority one operation with 

24/7 detection coverage, confirming that this was not a raid on Saipan like the one on 22 

February 1944 and that the invasion surface fleet was approaching the island, which Imperial 

High Command would confirm to Saitō.  

Japanese radar detection of TF 58 was essentially inevitable, as there were Japanese 

search radar emplacements located on Mañagaha, Naftan, Radar Hill, off Aslito Airfield, and 

potentially 2-3 search radar emplacements on Tinian within range of Saipan. The radar warning 

system over Saipan was incredibly layered, and it is unlikely that any US aircraft could surprise 

the island without their detection. Notably, the Japanese Mark 1 Model 3 radar emplacement had 

a maximum detection range of 300 km. of the US Mark III IFF (Identify Friendly or Foe) 

systems (Nakajima 1992:20). It acted as an installed military transponder on most US aircraft 

and surface naval vessels where radar pulses were transmitted and were read by an interrogator 

module of the IFF to determine friendly from enemy aircraft. Due to its operating frequency, 

though, it essentially lit an electromagnetic flare on its location for the radar scopes of the 

Japanese Mark 1 Model 3 search radar. 

The US naval bombardment began two days later, on 13 June 1944, near Naftan 

Peninsula and Aslito Airfield, but was inaccurate due to the inexperience of the crews in the 

naval bombardment and fears of getting too close since Saipan was falsely suspected of having 

been heavily mined (Hallas 2019:78-79). Throughout the battle, multiple waves of aircraft were 

launched to attack the island, where the aircraft were primarily F6F Hellcat fighters, Torpedo 

Bomber General Motors (TBM) and Torpedo Bomber Grumman (TBF) Avenger torpedo 

bombers, and SBD Dauntless dive bombers. Their targets from 11-15 June 1944 before the troop 

landings were primarily around the area of Tanapag Harbor, where the bulk of the Japanese 



 

24 

 

supply vessels were anchored (USS Lexington 1944a). Tanapag additionally functioned as the 

primary headquarters element of the IJN and IJA on the island (Hallas 2019:68) 

Being essential to the Japanese command structure on the island, Tanapag had extensive 

anti-aircraft emplacements located around it. Multiple emplacements were potentially linked and 

had wireless radio communication with the Mark 4 Model 3 fire-control radar on the island. The 

Mark 4 Model 3 fire-control radar AA emplacement was likely located less than two miles from 

Tanapag, enabling it to observe the approaching US aircraft when they lifted off from their 

carriers. The Japanese fire-control radar let the defenders know the altitude at which US aircraft 

were flying, their number, and their azimuth, and they had the aircraft automatically tracked. The 

fire-control radar then automatically relayed this information to anti-aircraft emplacements on 

the island through radio and AA directors or fire-control computers to set their guns and fuses to 

the appropriate setting to focus fire on a single target or formation (Nakagawa 1997:33-34). The 

US aircraft flew into a trap, unaware of the radar-directed flak awaiting them. Their 

overconfidence in their attack against Tanapag even caused them to refrain from conducting pre-

sortie reconnaissance of the site before their attack or considering a naval bombardment 

(USS Lexington 1944a). 

US aircraft arrived over Tanapag and was met with “heavy and accurate” anti-aircraft 

fire. US Navy historian Samuel Morison describes Japanese AA at Saipan as being "evident that 

Japanese anti-aircraft fire had vastly improved during the past year" (Morison 1953:178). They 

were saturated by flak on levels never seen before by the US in the Pacific Theater and were in 

complete confusion about the accuracy of the fire (USS Lexington 1944a). On the first day of the 

attack on 11 June 1944, there were already 13 US aircraft losses, and dozens of others were 

severely damaged from Japanese anti-aircraft flak fragmentation. Nearly all downed US aircraft 



 

25 

 

in Tanapag resulted from anti-aircraft fire (USS Lexington 1944a). The fire-control radar that 

assisted in this potentially remained operational until the capture of Radar Hill by the 1st 

Battalion 24th Marines on 3 July 1944 (Hoffman 1950:203). The transmitting and receiving units 

of the Mark 4 Model 3 were in near-pristine condition when it was captured, as it posed a tiny 

target for naval and aircraft bombardment and could easily be obscured. Following the battle, the 

Mark 4 Model 3 fire-control radar was acquired by US intelligence analysts and was potentially 

shown being filmed in the 13 July 1944 National Archives footage. US Intelligence was in 

complete shock by the capabilities of this module when its role as a fire-control radar was 

determined. The module was disassembled and shipped to the Naval Research Laboratory to 

develop countermeasures and jamming capabilities. The analysis determined that the radar was 

even more accurate than land-based fire-control radars that the US was fielding in the Pacific 

(Bonham and Lonsdale 1945). Testament to the accuracy of the Mark 4 Model 3 fire-control 

radar are the dozens of submerged aircraft around the coast of Saipan and in Tanapag Harbor. 

From 11 June 1944 to 9 July 1944, 81 US aircraft were downed over Saipan, with dozens of 

additional US aircraft being severely damaged and needing substantial mechanical repairs. 

Sixteen of these US aircraft losses were directly noted as having been lost to Japanese flak, 

having been assisted by Japanese fire-control radar (Appendix A). 

  



 

26 

 

CHAPTER 3 METHODOLOGY 

This chapter details the fieldwork methodology conducted to obtain the necessary 

archeological data for this thesis. The fieldwork was non-disturbance and relied heavily on 

photographic and pedestrian surveys. The chapter also describes the historical and archival 

research in the National Archives and through a Freedom of Information Act request. 

Additionally, this chapter describes the ArcGIS methodologies utilized that correlate the ranges 

of the Japanese radar emplacements on the island and the concentration of anti-aircraft fire with 

US aircraft during the battle. The chapter’s concluding section details the limitations encountered 

through the fieldwork and historical/archival research and how data could be hindered. 

3.1. SURVEY METHODOLOGY 

Fieldwork for this thesis was conducted in March 2022 and May 2023. The fieldwork 

focused on locating the terrestrial Japanese radar emplacement locations, utilizing non-

disturbance methodologies such as pedestrian survey, snorkel survey, and photography. Three 

locations of Japanese radar emplacements were determined through archival research prior to 

fieldwork: Radar Hill, Mañagaha Island, and Naftan Peninsula, as well as the confirmation of 

one dummy Japanese radar emplacement at the present PACBAR III Cold War radar on Saipan. 

The 2-3 Tinian radar emplacements were additionally considered as they were within range of 

Saipan. None of these sites had previously been identified as Japanese radar emplacements and 

had long lost their context and vital importance since the war's end. 

3.1.1. SITE SURVEY 

           Site formation processes were identified for each of the radar emplacement locations. This 

was primarily to understand the present terrain and foliage characteristics and how similar they 

were to when the battle occurred in 1944. This would help to understand how a radar 

 



 

27 

 

emplacement location was chosen. This understanding of the terrain of each Japanese radar 

emplacement location was primarily gained through various maps through the years since the 

battle to see progressive changes to a location's terrain and foliage. Multiple archival maps were 

used as a reference to represent the conditions during the battle and were compared to present 

Google Earth imagery of the site. Overlays of multiple maps were additionally created on 

ArcGIS and Google Earth to more clearly represent the changes to terrain and foliage over time. 

This was optimal for representing a clear line of sight of a location, which radar requires.  

Additionally utilized were various weather and local Saipan news reports that could help 

understand typical weathering or recent erosion qualities that may have affected the geographic 

appearance of the location. Often, human development considerations affected the status of the 

appearance of a Japanese radar archeological site. The natural weather erosion, sometimes more 

turbulent in the form of a hurricane, and nearly constant humidity eroded the aged metal and 

concrete structures. Thus, there needed to be an understanding at each location that the land's 

appearance could change dramatically in just 80 years. 

Secondarily, this information was obtained through the local knowledge of Fred 

Camacho and his local informants and observation. For example, on Radar Hill, the potential 

impact of wildfires was investigated as it has been subjected to wildfires. For example, in 2015, 

much of the unexploded ordnance in the region was cooked off and exploded through an out-of-

control wildfire. In 2023, Radar Hill was again subjected to wildfires, clearing the terrain and 

giving it a similar charred effect to how it had looked during the battle. The wildfires were 

optimal for this thesis as they quickly permitted a clear line of sight to be established for the 

submerged US aircraft in Tanapag Harbor and exposed the previously hidden IJN structures in 

the dense jungle. 



 

28 

 

After extensive background research of the site and what to expect at each, precedence 

was applied to known Japanese radar emplacement locations believed to have the most 

substantial archeological evidence and the slightest changes in terrain to represent a clear line of 

sight. Much notice was given to Radar Hill, not only through its name but also its proximity to 

all presently identified US downed aircraft in Tanapag Harbor, likely making it the emplacement 

location for the Mark 4 Model 3 fire-control radar. Thus, a pedestrian survey of the location was 

conducted in 2022 and 2023 with guide Fred Camacho. Photographs of the structures and 

artifacts were taken, with attention to electrical components, anti-aircraft casings, and Imperial 

Japanese Navy symbolism. The suspected radar employment field was comprehensively 

photographed to represent a clear line of sight, and 360-degree coverage was easily 

accomplished, as well as a clear line of sight to all of the submerged downed US aircraft sites in 

Tanapag Harbor. An Icarus drone was used in the radar employment field, where it was 

launched and flew vertically for 50 ft. and then at an azimuth to Tanapag Harbor to represent 

further the clear view the location would have had to US aircraft attacking the harbor.  

An attempt was then made to locate the Japanese radar emplacement on the Naftan 

Peninsula again with Fred Camacho, as he had been on Naftan multiple times and knew the area 

well. As limited archival and historical research had been conducted on the location at that time 

and given the density of the jungle during that time of year, the radar emplacement could not be 

located. Once the thesis author had felt there was a solid foundation for a comprehensive survey 

in 2023, a brief reconnaissance of Mañagaha was conducted with the author and an East Carolina 

University crew of a potential radar emplacement located there. Abnormalities in the terrain near 

the western shore were shown particular attention to. Due to the significant urban development 

on the land, little remains from the battle could be confidently established. 



 

29 

 

In 2023, a more thorough comprehensive survey of the building and structures was 

planned for Radar Hill, but due to last-minute concerns of the private property owners, the focus 

for the survey was then placed on the Naftan Peninsula radar emplacement. After a year and 

much archival work had been conducted on the location, the site was pinpointed on GPS 

coordinates so that Fred Camacho and the thesis author could more easily locate it. Additionally, 

photographs of the site were located online by a blogger who had been there 15 years prior, and 

Fred said he recognized the site from the pictures. Even with all the data, due to the density of 

the jungle, it took approximately two hours to locate the radar emplacement. Upon locating the 

site, GPS coordinates were taken of critical features of the structure to be easily represented on 

Google Earth and ArcGIS.  

After conducting a comprehensive survey of the Naftan Peninsula radar emplacement, 

additional survey work was permitted on additional suspected radar emplacement locations. As 

the pedestrian survey on Mañagaha Island yielded limited results, a snorkel survey was then 

conducted, focusing on the eastern and western approaches of the island where two East Carolina 

University teams examined the locations. The western survey was conducted because it had a 

clear line of sight to the ocean, as a US submarine was reported to have detected a Japanese radar 

emplacement on the island from the ocean. A snorkel survey was additionally conducted on the 

eastern face of the island, where multiple known battle-era artifacts remained in a submerged 

state. These structures and artifacts had multiple scaled photographs taken of them, focusing on 

features or electronics that might be related to a radar. Upon the completion of the fieldwork 

period, Radar Hill, the Naftan Peninsula, and Mañagaha Island were effectively surveyed in 

multiple aspects. 

3.2. ARCHIVAL AND HISTORICAL RESEARCH 



 

30 

 

           Archival and historical research was conducted before fieldwork was conducted. Archival 

sources needed to be used extensively as there has been limited modern authorship on Japanese 

radar. Research was focused on the following topics: 

● Radar fundamentals and era capabilities 

● Research and development of Japanese radar 

● IJN radar research and development 

● The battle for Saipan Japanese defensive organization 

● The battle for Saipan US aerial offensive organization 

● Mark 4 Model 3 fire-control radar 

● Japanese anti-aircraft weaponry and fire-control 

● Mark 1 Model 1 search radar 

● Mark 1 Model 2 search radar 

● Mark 1 Model 3 search radar 

3.2.1. HISTORICAL RESEARCH 

           The historical research focused on a broader understanding of WWII in the Pacific, 

Saipan’s role, and the radar theory of the era and its early development. This was accomplished 

through secondary text sources, interviews with radar technical experts, interviews with local 

Saipan cultural and historical subject matter experts, and review of the files of the Historic 

Preservation Office of the Commonwealth of the Northern Mariana Islands (CNMI). 

Historical research provided a better understanding of Japanese radar research and 

development from the 1930s to the war’s end. Using the sole historical text devoted to Japanese 

radar, Japanese Radar and Related Weapons of World War II (1998) by Yasuzo Nakagawa, a 



 

31 

 

complete understanding of the research and development of Japanese radar was able to be 

established. 

Due to the need for more technical expertise on the radar technology of WWII and its 

capabilities, subject matter experts were identified. Trent Telenko, who worked for 22 years as a 

quality control specialist for the Department of Defense’s Defense Contract Management 

Agency, was the primary expert available to help understand radar technology further. He retired 

as a quality technical lead specializing in assuring the technical capabilities of Department of 

Defense contracts, including radar technologies, with a personal research interest in Section 22, 

the covert Allied Japanese radar hunting unit. Through the assistance of Mr. Telenko, 

confirmation of the advanced technical abilities of Japanese radar was further established. 

Personal expertise was additionally used through a cultural and historical lens of Saipan 

via local guide Fred Camacho. Fred is a local Chamorro and has been hiking and exploring the 

island’s WWII history for over the last thirty years. Through his assistance, local oral narratives 

could be established on the studied radar emplacement locations and local names of the region, 

such as through the multiple etymological origins of Radar Hill, often relating directly to its 

“wireless” past.  

A partnership was additionally established with CNMI’s Historic Preservation Office 

(HPO). This was to utilize any potential archival data uncovered from the battle and previous 

survey work of the radar emplacement on the Naftan Peninsula. The Naftan Peninsula survey 

was conducted in 1996 to develop a Japanese resort that intended to cover most of the peninsula, 

thus the Naftan Peninsula Japanese radar emplacement was surveyed. The survey did not note 

the site’s significance or that it was utilized for Japanese radar. The earlier survey work 

documents were uncovered in HPO’s archival room. Unfortunately, the archival data from the 



 

32 

 

battle at HPO is minimal. HPO has been provided from the research of this thesis with a data 

cache of dozens of uncovered era archival battle documents. 

3.2.2. ARCHIVAL RESEARCH 

           Due to the lack of previous historical research conducted on Japanese radar during WWII, 

comprehensive archival research was needed. This archival data was predominately collected 

through digital collections. The primary sources are the digitized archival collection of the Ike 

Skelton Combined Arms Research Library in Fort Leavenworth, Kansas, and the National Diet 

Library in Tokyo, Japan. Additionally used was the digital collection of the Australian War 

Memorial in Campbell, Australia, and the Air Force Historical Research Agency and Air Force 

History Index in Montgomery, Alabama, for specialized data focusing on the capabilities of 

Japanese radar. The US National Archives and Records Administration (NARA) was utilized as 

well, particularly working with them to locate, declassify, and obtain documents relating to 

countermeasures research and development on the Mark 4 Model 3 fire-control radar at the 

Naval Research Laboratory in Washington, DC that was captured on Saipan through the FOIA 

(Appendix B).  

           The Ike Skelton Combined Arms Research Library contains the most comprehensively 

digitized World War II operational document collection. The collection is an essential resource 

as post-WWII, the Command and General Staff College at Fort Leavenworth was provided with 

these operational reports, including unit-based intelligence, logistics, and after-action reports 

(AARs) to provide further material to educate higher-ranking officers of captains and above as 

they are trained to command battalion sized elements where understanding these operational 

considerations are the most vital ingredients for success. The library contains a comprehensive 

digitized collection of captured and translated Japanese documents. Many of these documents 



 

33 

 

relate directly to the radar of the Japanese as well as their technical capabilities. Notably, the 

archives contain a comprehensive collection of intelligence reports from the battle for Saipan, 

which contain various maps and aerial photos used to construct the location of Japanese 

defensive fortifications throughout the island. 

           Japan's National Diet Library Digital Collections archives were utilized as they have 

comprehensively digitized World War II documents related to the Pacific War, especially 

documents concerning US Intelligence efforts against Japan. The archives proved especially 

useful with their comprehensive collection of US after-action reports from the bombing 

squadrons on the carriers. The digitized archives also contain records of the US Strategic 

Bombing Survey, including pre-invasion intelligence reports that proved extremely useful in this 

thesis. 

           The Australian War Memorial’s digital archives collection effectively obtained 

documentation determining the technical capabilities of individual Japanese radar emplacements. 

Comprehensive archival data on Japanese radar was obtained through the National Archives of 

Australia record search partnered with the Australian War Memorial. This was through the 

collected documentation at the Australian War Memorial of Section 22, a joint Australian and 

American Japanese radar search and destroy unit stationed in the Southwest Pacific Area. The 

unit focused its efforts on the detection and destruction of the Japanese Mark 4 Model 3 fire-

control radar that was first located on Saipan to develop countermeasures. The Australian War 

Memorial has documentation detailing how various Japanese radars work, operating frequencies, 

ranges, and their deadly technical efficiency. Multiple photographs and sketches from Section 22 

of the Japanese radar are provided, as well as maps that show the detected Japanese radar and the 

suspected locations, focusing on the Philippines and mainland Japan.  



 

34 

 

           The Air Force Historical Research Agency, located at Maxwell Air Force Base in 

Montgomery, Alabama, provides one of the most compressive microfilm archives dedicated 

primarily to the US Army Air Corps and the US Air Force. The collection is far more easily 

accessible than through NARA, as specific microfilm collections can be digitally requested and 

delivered with a rapid response. The desired microfilm can be located online through the Air 

Force History Index. Particularly important in the microfilm collection are translated Japanese 

documents relating to their radar usage as well as US intelligence summaries on the effectiveness 

of Japanese radar against US aircraft, such as the bombing missions over mainland Japan and the 

countermeasures that were developed. 

           The US National Archives and Records Administration was last utilized as an archival 

source for Japanese radar. Unfortunately, these digitized collections are minimal aside from unit 

“war diaries” that provided detailed unit accounts of unusually heavy Japanese anti-aircraft fire 

over Saipan. The undigitized documentation in NARA relating to Japanese radar is quite limited 

compared to the previous archival sources. However, NARA does have a comprehensive 

digitization of WWII footage. Post-battle footage showing the captured Japanese radar 

emplacements on Saipan that proved to be very useful in confirming location and status of the 

radar on Radar Hill and the Naftan Peninsula.  

The 81 US aircraft losses over Saipan from 11 June 1944 to 9 July 1944 were compiled 

through the Aviation Archaeological Investigation & Research organization's online database. 

The date of 11 June 1944 was chosen as the starting loss date from the start of the US aerial 

bombardment of the island to the end of the most organized Japanese resistance on 9 July 1944. 

The aircraft were determined through the US Navy Overseas Loss List 1941-1945 database, and 



 

35 

 

the losses over Saipan were compiled in a table (Appendix A). The loss circumstances were 

further confirmed though primarily Fold3’s digital military record collection. 

           All collected archival data relating to the battle for Saipan was compiled into a digital data 

cache, including countless rare maps, images, and intelligence reports. This data was shared with 

CNMI’s Historic Preservation Office and the National Parks Service located on Saipan to 

facilitate future displays and research on the battle. 

3.3. ANALYTICAL METHODOLOGY 

           Through the archival data uncovered, the Japanese radar emplacements were plotted on 

ArcGIS. Particular attention was given to era archival intelligence maps and current mapping 

imagery of Saipan. Through ArcGIS, these two maps were able to be georectified. The radar 

emplacements were plotted on ArcGIS using a “fields of fire” model developed previously by 

Aleck Tan. Through this model, the radar emplacements are represented in the fields of fire or 

principal sky watch areas of Japanese anti-aircraft gun emplacement units on the island are 

represented in areas of overlapping fire as well as the radar emplacements’ ranges and distances 

from known and suspected downed US aircraft locations.  

3.3.1. JAPANESE RADAR EMPLACEMENTS’ DETECTION RANGE GIS MODEL 

Japanese radar coverage was represented as a layer in the fields of fire ArcGIS model 

with 360-degree coverage and the radar modules’ specific detection ranges enabled. The 

overlapping radar detection ranges were then represented through the model. The circular ranges 

of each radar emplacement were represented with varying colors depending on the radar module 

utilized. The color green represented the ranges of the Mark 1 Model 1 search radar maximum 

detection range, blue for the Mark 1 Model 3 search radar maximum range, purple for the US 



 

36 

 

IFF detection maximum range of the Mark 1 Model 3 search radar, gray for the Mark 1 Model 2 

search radar, and red for the maximum range of the Mark 4 Model 3 fire-control radar. 

3.3.2. JAPANESE ANTI-AIRCRAFT EMPLACEMENTS FIELDS OF FIRE MODEL 

           The principal sky watch areas or fields of fire for the Japanese anti-aircraft defenses of the 

island were georectified through ArcGIS. The area that can be reached through Japanese AA unit 

weaponry acted as the unit’s fields of fire. From a captured Japanese map after the battle, the 

azimuth of each anti-aircraft unit was plotted throughout the island. This document was then 

georectified on ArcGIS where the ranges of each AA unit was represented with a triangular 

light-yellow shaded color field of fire of their respective principal sky watch area. The fields of 

fire of the Japanese AA units on Saipan were re-established on the created overlay on ArcGIS as 

triangular basic polygons. The transparency of the triangular fields of fire, represented in yellow 

color, was then adjusted to 20% for high values and 80% for low values to show the overlap in 

the fields of fire. The overlap of the fields of fire was more heavily represented through darker 

shades of yellow, which would likely represent the heaviest anti-aircraft fire from Japanese 

defenses on the island and the most likely downing locations of US aircraft. The overlapping 

results through ArcGIS can potentially predict where future magnetometer and survey work can 

be conducted to search for additional MIA US aircraft shot down by Japanese anti-aircraft during 

the battle.  

3.4. LIMITATIONS 

           The methodologies utilized in this thesis faced various and often entirely unforeseen 

limitations. The most significant limitation would be the ability to access fieldwork locations 

through various barriers of often privatized land. This was not a concern for the Naftan Peninsula 

radar emplacement and Mañagaha Island, as the suspected radar emplacement locations were on 



 

37 

 

public land. Meanwhile, the private landowners variably contested the Radar Hill site. The field 

where the radar was employed on Radar Hill is public, but the two-story IJN command post 

compound and separate one-story building are located on a private landowner’s property. For the 

2022 fieldwork season, the private landowners granted permission to conduct a reconnaissance 

pedestrian survey and were invited to conduct a more comprehensive one. With this 

consideration in mind, local guide and contact, Fred Camacho, and the thesis author remained in 

contact and coordinated an additional survey in the months preceding the May 2023 fieldwork 

season. Without further explanation and despite repeated attempts, access to survey the Radar 

Hill structures was denied. Attempts were also made to locate the radar emplacement 1,300 yds. 

off the east end of Aslito airfield in Dandan Village. Due to the location’s residential nature and 

urban development, only select private landowners in the area could be contacted to give 

permission to locate potential archeological remains of the Japanese structure on their property. 

The ability to properly photograph and survey was also limited through sites on private 

land and the heavy vegetation of the remote fieldwork sites in the jungle. Dense vegetation 

would often block the camera’s field of view, especially at the Naftan Peninsula radar 

emplacement. Attempts were made to create a 3-D model of the Naftan Peninsula radar tower 

through Rhino modeling software using multi-perspective and angular 360-degree photos. The 

vegetation was so dense that a distanced perspective of the radar tower could not be adequately 

achieved, and only approximately 50 percent of the 3-D model of the radar tower could be 

rendered. An effort was made to remedy this limitation by using a drone planned to be launched 

from the radar tower to provide an aerial and clearer perspective, filming it with 360-degree 

coverage to fully render a model of the tower. Unfortunately, the radar emplacement was just on 



 

38 

 

the boundary limits of Isley Airport, where the Federal Aviation Administration had exclusive 

permissions for the airspace, and the drone was not permitted to launch. 

           The environmental survey was limited to the need for comprehensive annual island 

mapping. Before the early 2000s, the island’s satellite imagery was relatively poor, and yearly 

aerial photography was unavailable for multiple years. The survey focused on the erosion 

qualities of Mañagaha Island that occurred sometime in the early 1980s. Due to the lack of data 

available, it could not be confidently determined what precise year the suspected radar 

emplacement location and Type 96 AA guns became submerged on the eastern face of the island. 

           The historical research was limited as there has been virtually no historical authorship on 

Japanese radar, particularly through secondary sources. Much of this lack of authorship on 

Japanese radar is through the continued and repeated Pacific War myth of Japanese technical 

inferiority regarding their abilities in radar. Many Pacific War narratives are entirely ignorant 

and often do not even mention the usage of Japanese radar during the war.  

           Archival research was only slightly limited, as nearly all the required documentation was 

found to be digitized through the archives of the Ike Skelton Library at Fort Leavenworth, 

Kansas. There were some accessibility issues in accessing archival data on Japanese radar that 

had not been digitized through some sources. Accessibility was particularly an issue with The 

National Archives and Records Administration, where virtually none of