have expected them to fire on the Marine reconnaissance aircraft if they were operational. Unlike the larger islands of the Marianas, Rota was not initially heavily fortified by the Imperial Japanese military during World War II. On December 9, 1941, the Japanese Guam Invasion fleet from Haba Jima and Saipan rendezvoused at Rota; however, none of the forces occupied the island (Rottman 2002:394). The size of the Japanese occupation force present on Rota after the start of World War II is under debate. Moore and Hunter-Anderson (1988:19) indicate that there was little information concerning the size and makeup of the Japanese garrison at Rota prior to 1944. However, Peck (1986:5) suggests that there were only six Japanese soldiers on Rota in January 1944. Moore and Hunter-Anderson (1988:19) disagree with this low number because the construction of the military airfield would have required a larger military engineering detachment than six soldiers. Using information provided in Crowl (1960:60), Moore and Hunter-Anderson (1988:19) and Denfeld (1997:129) estimate that there were less than 3,000 Japanese troops on Rota in June 1944. These troops and supplies that arrived in June were the last reinforcements to reach Rota prior to the Japanese surrender (Moore and Hunter-Anderson 1988:19). The islands of the Marianas were seen as points in a larger patrol network and did not require Japanese Army troops for their defense. After the fall of the Marshall Islands, the Japanese military began to reinforce the Mariana Islands. The importance of protecting the Mariana Islands was illustrated when Japanese leaders stated that “the Mariana Islands are Japan's final defensive line. Loss of these islands signifies Japan’s surrender” (Shaw et al. 1966:442). US Marine Corps intelligence indicated that before February 1944 the Imperial Japanese Navy was in charge of the defense of Guam and the other Mariana Islands. The intelligence also indicated that the 54th Guard Unit (KEIBITAI; 警備隊) was the nucleus of the defense of Guam, so it is possible that a similar situation existed on Rota (HQ, Fleet Marine Force Pacific 1944:43). Naval documents show that elements of the 56th Guard unit (KEIBITAI; 警備隊) were located at Rota and Tinian. Guard units were naval units that served as the “nuclei for the defense of the area in which they are located” (CinCPac-CinCPOA Bulletin 11-45:3, 9–10). In addition to the 56th Guard Unit, the Imperial Japanese Navy had the 223rd Construction Battalion (SETSUEITAI; 設営隊) located at Rota and Saipan. Like the
Marianas History Conference 2012 ・ 35