In December 1941, the Japanese invasion of Burma opened what would be the longest land campaign for Britain of the entire war. It began with defeat and pell-mell retreat, as Rangoon fell to the invader in March 1942. British, Indian and Chinese forces were driven back into India. The fighting would stretch on, over a varied terrain of jungles, mountains, plains and wide rivers, stopping only for the monsoon, until Japanese surrender in 1945.
After the initial retreat, the British began to rebuild their army and resources from Assam in north-eastern India. This process was slow because priority was given to the war against Germany. The British position was also complicated by discontent in India, the result of British failure to clearly address the issue of post-war independence. The Japanese capitalised on this anti-British sentiment, recruiting captured Indian troops into the 40,000 strong Indian National Army, commanded by Subhas Chandra Bose, that fought alongside the Japanese.
With most of the Chinese coast under Japanese control, the Burma Road was the main supply route available to the Chinese Nationalists, fighting the Japanese in China. This gave the Burmese campaign great strategic importance. In December 1942, a limited British offensive to capture the Arakan coastal region met with failure. The only glimmer of hope came from the Chindits, long range penetration groups which waged guerrilla war in the Burmese jungle. Despite limited military success, their exploits boosted public morale.
Throughout 1943, the horizon looked bleak for the British, who lacked the resources and organisation to recapture Burma. In November 1943, the South East Asia Command was formed to centralise and organise Allied forces. General Slim slowly rebuilt morale and forged an efficient offensive combat force: the cosmopolitan Fourteenth Army, made up of British, Indians, Gurkhas, and East and West Africans.
The Japanese had also been regrouping. On 7 March, Operation U-Go was launched. Although this bold attempt to invade India surprised the Fourteenth Army, new tactics and growing confidence ensured that they maintained their positions on the crucial roadways to India. When Slim's forces found themselves surrounded at Imphal and Kohima, an epic struggle ensued. The British Commonwealth forces, thanks to air resupply, managed to drive the Japanese into retreat, causing the largest defeat ever suffered by the Japanese army. Of the 85,000 soldiers, 30,000 were killed.
The Fourteenth Army now went on the offensive. By October 1944, it had crossed the river Chindwin and was approaching Mandalay and Meiktila. After two months of arduous combat in a coastal zone of reservoirs and river deltas, Meiktila was taken on 4 March 1945. Two months later, an ambitious amphibious operation allowed Slim's army to re-enter Rangoon on 6 May 1945. Although this was effectively the end of the campaign, the remaining Japanese forces in Burma did not surrender until 28 August 1945.