Japanese occupation of Thailand

Thailand in World War II officially adopted a position of neutrality until it was invaded by Japan in December 1941. At the start of the Pacific War, the Japanese Empire pressured the Thai government to allow the passage of Japanese troops to invade British-held Malaya and Burma. The Thai government under Plaek Phibunsongkhram (known simply as Phibun) considered it preferable to co-operate with the Japanese rather than fight them. Axis-aligned Thailand declared war on the United States and Britain and annexed territories in neighbouring countries, expanding to the north, south, and east, gaining a border with China near Kengtung.

Thailand retained control of its armed forces and internal affairs. The Japanese policy on Thailand differed from their relationship with the puppet state of Manchukuo. Japan intended bilateral relationships similar to those between Nazi Germany and Finland, Bulgaria, and Romania. However Thailand at that time has been labelled by both the Japanese and the Allies as the "Italy of Asia"

Meanwhile the Thai government had split into two factions, the Phibun regime and a well-organised, pro-Allied resistance movement that eventually numbered around 90,000 Thai guerrillas, supported by government officials allied to the regent Pridi Phanomyong. The movement was active from 1942, resisting the Phibun regime and the Japanese. The partisans provided espionage services to the Allies, performed some sabotage activities, and helped engineer Phibun's downfall in 1944. After the war, Thailand received little punishment for its wartime role under Phibun.

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