 By June 1945 around 550 Japanese military personnel were stationed on Labuan . The main unit on the island was the 371st Independent Infantry Battalion ( almost in its entirety , save for one company located elsewhere ) with a strength of around 350 . This battalion formed part of the 56th Independent Mixed Brigade , which had arrived at Tawao in north @-@ east Borneo from Japan in July 1944 with six infantry battalions . During early 1945 the brigade headquarters , 371st Independent Infantry Battalion and three other battalions marched across the island to assume responsibility for defending the Brunei Bay area . Many of the 56th Independent Mixed Brigade 's soldiers fell sick during the march , and all four combat battalions were considerably below their authorised strength by the time they arrived at Brunei Bay . In June 1945 the 371st Independent Infantry Battalion was commanded by Captain Shichiro Okuyama . A detachment of about 50 men from the 111th Airfield Battalion was also on Labuan , along with around 150 men assigned to other small units . In line with Japanese doctrine , the Labuan garrison did not make preparations to contest the Allied landing force as it came ashore . Instead , it constructed defensive positions inland from the island 's beaches . Documents captured by Australian soldiers during the fighting on Labuan indicated that Okuyama had instructions to attempt to withdraw his force from the island if the battle went against him . 
