the U.S. Army's 727th Amphibian Tractor Battalion, Co. A, who manned the LVTs and United States Navy Seabee detachments aboard the Landing Ship Tanks. The Dutch forces were organised into a company of Ambonese infantry commanded by Dutch officers and a civil affairs unit. Japan At the time of the Allied landing, the Japanese force on Tarakan numbered 2,200 men drawn from the Imperial Japanese Army and Imperial Japanese Navy. The largest unit was the 740-man strong 455th Independent Infantry Battalion which was commanded by Major Tadao Tokoi (). 150 Army support troops were also on Tarakan. The Navy's contribution to Tarakan's garrison comprised 980 seamen commanded by Commander Kaoru Kaharu. The main naval unit was the 600-strong 2nd Naval Garrison Force. This naval unit was trained to fight as infantry and operated several coastal defence guns. The 350 Japanese civilian oil workers on Tarakan were also expected to fight in the event of an Allied attack. The Japanese force included about 50 Indonesians serving in a home guard unit. Major Tokoi directed the overall defence of Tarakan, though relations between the Army and Navy were poor. The Japanese forces were concentrated around Lingkas, Tarakan's main port and the site of the only beaches suitable for landing troops. These defenders had spent the months before the invasion constructing defensive positions and laying mines. These fixed defences were used extensively during the battle, with Japanese tactics being focused on tenaciously defending pre-prepared positions. The Japanese did not conduct any large counter-attacks, and most offensive actions were limited to small parties of raiders which attempted to infiltrate the Australian lines. Preparatory operations The Japanese force on Tarakan was warned of the impending invasion in April, before the Allies began their pre-invasion bombardment of the island. The island's commander received a radio signal warning him of imminent attack, and the commander of Tarakan's oil depot was ordered to destroy the oil wells on 15 April. It is possible that this warning may have been issued as a result of a security leak from either the Chinese Republican Army's representative to Australia or MacArthur's headquarters. This did not have any effect on the subsequent battle, however, as the Japanese had been preparing defences to resist invasion for several months and the Japanese were aware of the large Allied force which was being assembled at Morotai to attack Borneo. Prior to the arrival of the