A major battleground, Burma was devastated during World War II. By March 1942, within months after they entered the war, Japanese troops had advanced on Rangoon and the British administration had collapsed. A Burmese Executive Administration headed by Ba Maw was established by the Japanese in August 1942. Wingate's British Chindits were formed into long-range penetration groups trained to operate deep behind Japanese lines. A similar American unit, Merrill's Marauders, followed the Chindits into the Burmese jungle in 1943. Beginning in late 1944, allied troops launched a series of offensives that led to the end of Japanese rule in July 1945. However, the battles were intense with much of Burma laid waste by the fighting. Overall, the Japanese lost some 150,000 men in Burma. Although many Burmese fought initially for the Japanese, some Burmese, mostly from the ethnic minorities, also served in the British Burma Army. The Burma National Army and the Arakan National Army fought with the Japanese from 1942 to 1944, but switched allegiance to the Allied side in 1945.