The Burma Campaign in the South-East Asian Theatre of World War II was fought primarily by British Commonwealth, Chinese and United States forces against the forces of the Empire of Japan, who were assisted to some degree by Thailand, the Burmese Independence Army and the Indian National Army. The British Commonwealth land forces were drawn primarily from the United Kingdom, British India and Africa. In a final operation just before the end of the war, Japanese forces which had been isolated in Southern Burma attempted to escape across the Sittang River, suffering heavy casualties.