The Burma campaign was a series of battles fought in the British colony of Burma, South-East Asian theatre of World War II, primarily involving the forces of the British Empire and China, with support from the United States, against the invading forces of Imperial Japan, Thailand, and collaborator units such as the Burma Independence Army, which spearheaded the initial attacks against British forces, and the Indian National Army. British Empire forces peaked at around 1,000,000 land and air forces, and were drawn primarily from British India, with British Army forces (equivalent to 8 regular infantry divisions and 6 tank regiments), 100,000 East and West African colonial troops, and smaller numbers of land and air forces from several other Dominions and Colonies.
The campaign had a number of notable features. The geographical characteristics of the region meant that weather, disease and terrain had a major effect on operations. The lack of transport infrastructure placed an emphasis on military engineering and air transport to move and supply troops, and evacuate wounded. The campaign was also politically complex, with the British, the United States and the Chinese all having different strategic priorities.
It was also the only land campaign by the Western Allies in the Pacific Theatre which proceeded continuously from the start of hostilities to the end of the war. This was due to its geographical location. By extending from Southeast Asia to India, its area included some lands which the British lost at the outset of the war, but also included areas of India wherein the Japanese advance was eventually stopped.
The climate of the region is dominated by the seasonal monsoon rains, which allowed effective campaigning for only just over half of each year. This, together with other factors such as famine and disorder in British India and the priority given by the Allies to the defeat of Nazi Germany, prolonged the campaign and divided it into four phases: the Japanese invasion, which led to the expulsion of British, Indian and Chinese forces in 1942; failed attempts by the Allies to mount offensives into Burma, from late 1942 to early 1944; the 1944 Japanese invasion of India, which ultimately failed following the battles of Imphal and Kohima; and finally the successful Allied offensive which reoccupied Burma from late-1944 to mid-1945.