Petroleum production in selected East Asian countries 1900-1945, by country

In the early 1900s, the Dutch East Indies (present-day Indonesia) was the largest producer of crude petroleum in the Pacific. Following the U.S. cessation of oil exports to Japan in 1941, and the lack of oil access at home, Japan's invasion of China was at threat of coming to a halt. In order to keep its armies supplied, Japan launched an invasion of Southeast Asia on December 8. 1941, with the annexation of Indonesia as one of its top priorities. This invasion also included the attack on Pearl Harbor, where Japan sought to neutralize the U.S. Pacific Fleet to prevent American interference. This brought the U.S. military into the Second World War, but it was not until mid-1942 when the Allies then halted the Japanese advance in Southeast Asia and started pushing them back through Southeast Asia in a grueling three-year long campaign. One of the keys to the Allies' success was the disruption of Japan's oil supply from Indonesia to Japan's armies in China and at home.