Americans strongly opposed Japan's invasion of China in 1937. President Roosevelt imposed increasingly stringent economic sanctions intended to deprive Japan of the oil and steel, as well as dollars, it needed to continue its war in China. Japan reacted by forging an alliance with Germany and Italy in 1940, known as the Tripartite Pact, which worsened its relations with the US. In July 1941, the United States, Great Britain, and the Netherlands froze all Japanese assets and cut off oil shipments—Japan had little oil of its own.
