 The battalions of the Burma Rifles which formed most of the 1st Burma Division were originally raised as internal security troops only, from among minority communities in Burma such as the Karens.They also had been rapidly expanded, with an influx of Bamar soldiers, and were short of equipment and consisted mainly of new recruits.Japan entered the war primarily to obtain raw materials, especially oil, from European (particularly Dutch) possessions in South East Asia which were weakly defended because of the war in Europe.