Embargo that prohibited export of fuel and other war materials to Japan in the years preceding World War II.
In 1937 Japan and China began the second Sino-Japanese War, a war that would ultimately last until 1945. Because the fighting encroached on their trade and activities in the region, the Soviet Union, the United States, and Britain experienced a decline in their relations with Japan, and despite their protests Japan was determined to expand its territory. Moving outward from Manchukuo (the portion of Manchuria Japan had taken over in 1932), the Japanese also invaded eastern Mongolia. However, combined Soviet and Mongolian troops won a victory in 1939 that influenced Japan to instead move south toward China and Southeast Asia.
In 1940, Japanese Prime Minister Konoe Fuminaro called for the creation of a Greater East Asia Co-Prosperity Sphere to consist of Japan, China, Manchukuo, and Southeast Asia.
Under this plan, a Japanese-led Asia would be able to compete economically with the West. As a result of Japan’s earlier expansion, in July 1940 the United States placed embargoes on war supplies destined for Japan. Specifically, the United States restricted the export of scrap metal and high-octane aviation fuel. Although the embargo was designed to stop Japanese expansion, it was incomplete and so proved ineffective.
Japan’s relationship with the United States and Britain further deteriorated in September 1940, when Japan invaded Indochina and joined the Axis powers as a result of the Tripartite Pact. In April 1941, the Japanese signed a neutrality agreement with the Soviet Union and began making active war plans against the United States. Peace talks to avoid conflict deadlocked. Germany’s invasion of the Soviet Union in June 1941 ended the Russian threat to Japan near Mongolia and, in July, Japan moved against the Dutch East Indies for its oil and rubber supplies. In response the United States froze Japanese assets in America and began a complete oil embargo against Japan. The British and Dutch did the same, and the cooperative embargo slashed Japanese oil imports by 90 percent.
Initially meant as a deterrent, the embargo rapidly led to economic warfare. Heavily dependent on outside petroleum sources, the Japanese felt pressured to confront the United States and to increase its supply of oil by capturing oil supplies in the East Indies before their stockpiles ran out. In response, the Japanese attacked Pearl Harbor on December 7, 1941, and full-fledged warfare broke out between Japan and the United States in the Pacific as the United States entered World War II against the Axis powers.