The war had not been confined to Europe. On 27 September 1940, Japan, Germany and Italy signed a pact and on 7 December 1941 Japan bombed the US Pacific Fleet naval base at Pearl Harbour. It went on to invade and occupy Burma, Malaya, Singapore and the Dutch East Indies with very little difficulty. The Allied fleet under the command of Dutch Rear Admiral Karel Doorman was defeated in the Battle of the Java Sea with the loss of almost all the Australian, British, American and Dutch vessels involved and thousands of men on board them (including 900 Dutch citizens).

The Dutch land-based troops in the region were forced to capitulate after three months. Over the next few months, all Dutch citizens in the region were interned in separate men's and women's camps. In itself the experience was deeply humiliating for the Dutch colonial elite and the ill-treatment they received in the camps at the hands of the Japanese military made it even worse. The prisoners were subject to strict discipline and a starvation diet, and many died.

The attitude of the Indonesians was initially ambiguous. They were uncertain whether to regard the Japanese as liberators or occupiers. Prior to the outbreak of the Second World War, the country had already had a nationalist movement headed by Sukarno and his Partai Nasional Indonesia (PNI). The Japanese exploited this movement for their own ends and the whole nation was yoked to the Japanese war effort. Hundreds of thousands of Indonesians were treated as slave labourers, as were the male Dutch prisoners of war.

In the summer of 1942, America was able to halt the Japanese advance. The US navy gradually gained the upper hand in the Pacific with victory in the Battle of the Coral Sea (7-8 May 1942) and the Battle of Midway (3-6 June 1942), and US forces returned to the Philippines in October 1944. On 6 August an atomic bomb was dropped on Hiroshima killing 140,000 people, followed three days later by another on Nagasaki killing an estimated 70,000 more. This ended the war. Japan formally capitulated on 2 September 1945 and immediately began its withdrawal from the areas it still occupied.