The Burma Campaign in the South-East Asian Theatre of World War II was fought primarily between British Commonwealth, Chinese and United States forces against the forces of the Empire of Japan, Thailand, and the Indian National Army. British Commonwealth land forces were drawn primarily from British India. The Burmese Independence Army was trained by the Japanese and spearheaded the initial attacks against the British forces..
The campaign had a number of notable features. The geographical characteristics of the region meant that factors like 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, Americans and 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 the areas of India where the Japanese advances were 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.
Japanese objectives in Burma were initially limited to the capture of Rangoon, the capital and principal seaport. This would close the overland supply line to China and provide a strategic bulwark to defend Japanese gains in Malaya and the Dutch East Indies. The Japanese Fifteenth Army under Lieutenant General Shojiro Iida, initially consisting of only two infantry divisions, moved into northern Thailand (which had signed a treaty of friendship with Japan), and launched an attack over jungle-clad mountain ranges into the southern Burmese province of Tenasserim in January 1942.
The Japanese successfully attacked over the Kawkareik Pass, and captured the port of Moulmein at the mouth of the Salween River after overcoming stiff resistance. They then advanced northwards, outflanking successive British defensive positions. Troops of the 17th Indian Division tried to retreat over the Sittang River, but Japanese parties reached the vital bridge before they did. On 22 February, the bridge was demolished to prevent its capture, a decision that has since been extremely contentious.
The loss of two brigades of 17th Indian Division meant that Rangoon could not be defended. General Archibald Wavell, the commander-in-chief of the ABDA Command, nevertheless ordered Rangoon to be held as he was expecting substantial reinforcements from the Middle East. Although some units arrived, counterattacks failed and the new commander of Burma Army (General Harold Alexander), ordered the city to be evacuated on 7 March after its port and oil refinery had been destroyed. The remnants of Burma Army broke out to the north, narrowly escaping encirclement.