 In Sep 15, 1939 American oil companies unveiled contracts to deliver three million barrels of petroleum to the Japanese Navy.Japan invaded and occupied the northern part of French Indochina (present-day Vietnam, Laos, Cambodia) in September 1940 to prevent China from receiving the 10,000 tons of materials delivered monthly by the Allies via the Haiphong–Yunnan Fou Railway line.On June 22, 1941, Germany attacked the Soviet Union.