In 1941, the division was assigned to the 15th Army and participated in the Japanese conquest of Burma. The division had the 143rd Regiment detached to separately capture Dawei (Tavoy) and Myeik (Mergui), while the main troop had captured Mawlamyine (Moulmein) on 31 January 1942. In March 1942 the division fought for 14 days around the city of Taungoo against the weakened Chinese 200th Division. The fight ended when the Chinese broke through and disengaged. On 18 April 1942, the 55th Division had encircled the Chinese 55th Division, eventually wiping it out. During the Burma Campaign, the 144th Infantry Regiment was detached from the division and sent to New Guinea. The rest of the 55th was used to counter an ill-planned British attack at Donbaik (Sittwe (Akyab)) from 18 March 1943. By 3 April 1943 the division had started to advance past the Mayu range, eventually surrounding and defeating a number of British units; encountering stiffer resistance from May 1943 onwards. Mid November 1943 the 55th was still in the Arakan area. Finally, the division fought a failed offensive which become the Battle of the Admin Box in February 1944. On 19 February 1944, the commander of the 112th Infantry Regiment, at that time down from 3000 to 400 men, had broken radio communication with the division headquarters and withdrew his men. In the aftermath of the disastrous Battle of Imphal, the division was assigned to the 28th Army in Burma and, after retreating to the Irrawaddy river, was subordinated to 38th Army. On 15 August 1945, when the Surrender of Japan was spoken out, the 55th Division was in Phnom Penh.