Thailand was invaded by Japan during World War II in the 1941 invasion. At the start of the Pacific War, the Japanese Empire leaned on the Thais to allow passage of Japanese troops on their way to invade British-held Malaya and Burma. This was not popular with much of the population, but the Thai government under Plaek Phibunsongkhram (known simply as Phibun) thought it preferable to outright Japanese conquest. After Thailand agreed to let Japanese troops pass through the country, the Japanese then allied with Thailand and later Thailand declared war on the Allies.