Five Days in June: The Archaeological and Historical Legacy of Saipan's Open Ocean Seadrome

Abstract

Saipan’s open ocean seadrome was an unconventional and expedient solution to an emergent operational challenge. Operation FORAGER, the invasion of the Northern Marianas, was unexpectedly contested by the Japanese First Mobile Fleet. The United States Fifth Fleet immediately implemented an expedient non-traditional seadrome in the open ocean for emergent long-range searches. It accepted and managed significant operational risk by establishing and operating this atypical seadrome outside a sheltered anchorage — and in harm’s way — to support vital PBM-3D Mariner seaplane night Radio Direction and Ranging search operations. Previous archaeological efforts have yielded a commanding knowledge of the traditional seadrome in Saipan’s Tanapag Harbor. Surveys of the captured Japanese seaplane base with existing infrastructure have contributed markedly to the archaeological record. A more thorough effort devoted explicitly to the innovative, high-risk, high-reward implementation of the initial open ocean seadrome and its contribution to the archaeological record has yet to be undertaken. This open ocean seadrome, established in the opening days of the battle, provided the initial long-range search crucially required for the security of the United States Fifth Fleet. Assessing the impact these patrol planes had on the conduct and outcome of the battle informs an underreported, yet critical, aspect of the Battle of the Philippine Sea. This facility also served as an essential proof of concept that demonstrated the temporary viability of an open ocean seadrome. Lessons from this evolution heavily informed future Pacific seadromes and seaplane tender support requirements. Although the exact location of this seadrome remains speculative, archival resources provide the level of geographic fidelity needed to conduct an appropriate archaeological site survey. A PBM-3D maritime patrol seaplane accidentally sank at this anchorage, but without the catastrophic damage and dislocation generally associated with traditional aircraft crashes. Locating, surveying, and recording this aircraft in situ would theoretically provide consequential site formation and cultural and environmental impact data. Other associated archaeologically significant artifacts may also be present. These artifacts would further contribute to and validate the archaeological record and inform open ocean seadrome operational practices and seaplane tender support activities. The open ocean seadrome was established upon the Saipan Shelf, the invasion's primary amphibious force staging area. The potential for opportunistic incidental artifact discovery to inform the archaeological interpretation of the battle should also not be underestimated. This area is approximately 100 feet (31 meters) deep. Search efforts included traditional methods and sought to inform the viability and reliability of leveraging various detection technologies, such as Light Detection and Ranging, adapted for maritime archaeological surveys. Geographic Information Systems software and data were utilized to establish search areas and parameters based on historical records and to assist in mapping the locations of any cultural material associated with the open ocean seadrome. Experimentation with these technologies contributes to their continued development and integration into existing archaeological methods, improving their future effectiveness.