In 1931, a dispute near the Chinese city of Mukden (Shenyang) precipitated events that led to the Japanese conquest of Manchuria. In response, U.S. Secretary of State Henry Stimson issued what would become known as the Stimson Doctrine, stating that the United States would not recognize any agreements between the Japanese and Chinese that limited free commercial intercourse in the region.
Japanese expansion threatened US interests in Asia
In the 1920s and 1930s, the United States had a number of interests in the Far East. The United States engaged in trade and investment in China. American missionaries representing many denominations worked within the region. The United States also claimed Pacific territories, including the Philippines, Guam, and Hawaii.
The United States defended its interests in the region through a three-pronged Far Eastern policy: it included the principle of the Open Door for guaranteeing equal access to commercial opportunities in China, a belief in the importance of maintaining the territorial integrity of China, and a commitment to cooperation with other powers with interests in the region.