sentences:  Aung San briefly returned to Burma to enlist twenty-nine young men who went to Japan with him to receive military training on Hainan, China, and they came to be known as the "Thirty Comrades".When the Japanese occupied Bangkok in December 1941, Aung San announced the formation of the Burma Independence Army (BIA) in anticipation of the Japanese invasion of Burma in 1942.For Japan's military leadership, the conquest of Burma was a vital strategic objective upon the opening of hostilities with Britain and the United States.