Mouwembleem SACSEA South East Asia Command

The initial supreme commander of the theatre was General Sir Archibald Wavell while head of the short-lived American-British-Dutch-Australian Command (ABDACOM) which was dissolved after the fall of Singapore and the Dutch East Indies. On 30 March 1942 the Joint Chiefs of Staff issued instructions naming General Douglas McArthur as commander-in-chief of the South West Pacific Area, which was made responsible for the water areas of the South China Sea, Borneo, and Java.

In August 1943, the Allies created the combined South East Asian Command, to assume overall command of air, sea and land operations in the theatre. In August 1943, with the agreement of the Combined Chiefs of Staff, Winston Churchill appointed Admiral Lord Louis Mountbatten as Supreme Allied Commander South East Asia. US Army General Joseph Stilwell was appointed deputy supreme commander. Stilwell was also, officially, deputy to Chiang Kai Shek, as Allied commander in China, and commanded all US forces across both theatres (which were known in the US as the China Burma India (CBI) Theater). Meanwhile the British Army commander in India, Auchinleck as Commander-in-Chief, India, provided vital base support.