Imperial Japan was very much a martial society, one in which the armed forces enjoyed a high level of prestige and influence. Combined with an intense nationalism, the militarization of Japanese life had turned the country into an aggressive power, willing and able to wage war. All of the available evidence suggests that the Japanese had been preparing for war in South East Asia since at least 1936. Yet it took the outbreak of World War II in Europe for the Japanese high command to put its long-standing military strategy into effect.
Large parts of South East Asia belonged to European imperial powers, mainly Great Britain and France. Emboldened by its successes in Manchuria, the Japanese invaded British colonial territories, such as Hong Kong and Singapore. The British were unable to put up much resistance to the Japanese, as they were bogged down in fighting the Germans in Europe and so were dangerously overstretched in relation to defending their empire. The Japanese were also able to take advantage of the weakness of a defeated France to invade and occupy French Indochina.