The Burma campaign in the South-East Asian Theatre of World War II took place over four years from 1942 to 1945. During the first year of the campaign, the Imperial Japanese Army with aid from Burmese insurgents had driven British forces and Chinese forces out of Burma, and occupied most of the country. From May to December 1942, most active campaigning ceased as the monsoon rains made tactical movement almost impossible in the forested and mountainous border between India and Burma, and both the Allies and Japanese faced severe logistical constraints.