The Japanese defending the island, the 50th Infantry Regiment, which was originally part of 29th Division, were commanded by Colonel Kiyochi Ogata. On May 12, 1943, there were also 2,349 Marines of the 3rd Special Forces Unit (第 3 特別 根 地 隊, Dai-3 Tokubetsu Konkyochitai) and 950 marines of the 56th Naval Guards, who had been transferred there from Truk. These soldiers were under the command of Kaigun-Taisa Goichi Oya. The naval forces took over the defense of the airfields, as they belonged to the facilities of naval aviation. The Japanese naval troops also took over all the heavy artillery guns around the airfields and the 39 heavy anti-aircraft guns, which were set up directly around the slopes. In addition, there were construction crews, flight technicians and staff, so that a total of about 4,110 soldiers of various units defended the airfields. Vice-Admiral Kakuji Kakuta, commander of First Air Fleet, was headquartered in Manila, but was on Tinian on an inspection tour when the invasion started. Kakuta exercised no command authority over the army troops on the island, and also the naval troops were not subject to his direct command.