寺内寿一
The Southern Expeditionary Army Group under overall command of Hisaichi Terauchi was responsible for all military operations in the South-East Asia. The Japanese Fifteenth Army, commanded by Lieutenant General Shojiro Iida, was initially assigned the mission of occupying northern Thailand, which had signed a treaty of friendship with Japan on 21 December 1941, and attacking the southern Burmese province of Tenasserim across the Tenasserim Hills. The army consisted of the highly regarded 33rd Division and the 55th Division, although both divisions were weakened for several weeks by detachments to other operations.