For the first six months the Japanese advance was virtually invincible: Hong Kong, Malaya, Singapore, Java and the Indies, the Philippines, Burma and the Andaman Islands, New Britain and the Solomons all fell to Japanese arms. However, a grave miscalculation of the spirit and resources of the nation's principal enemies had been committed by the Japanese leaders. Allied submarines, US island-hopping strategy and superior fire-power led to a reversal of Japan's position. From mid-1944 the fate turned against Japan. By mid-1945 military collapse was about to happen. When the United States dropped atomic bombs on Hiroshima and Nagasaki in the summer of 1945, a complete collapse of the empire and surrender ensued. A military occupation, chiefly by US forces, lasted from 1945 to 1952. In 1947, Japan adopted a new constitution under US direction, renouncing war, granting basic human rights, and declaring Japan a democracy (O'Brien, 2000).
US General Douglas MacArthur represented all the Allies in Japan after its defeat, but the occupation was nevertheless an almost exclusively US undertaking and to a very great extent MacArthur took his own decisions, without direct reference to Washington. He rejected the view that the Japanese would be better off without the age-old institution of the monarchy.