In 1931, Japan invaded Manchuria, defeating the Republic of China's military forces and establishing Manchukuo, a puppet state. The Hoover administration deplored the invasion, but also sought to avoid antagonizing the Japanese, fearing that taking too strong of a stand would weaken the moderate forces in the Japanese government. Hoover also viewed the Japanese as a potential ally against the Soviet Union, which he saw as a much greater threat. In response to the Japanese invasion, Hoover and Secretary of State Stimson outlined the Stimson Doctrine, which held that the United States would not recognize territories gained by force. The Hoover administration based this declaration on the 1928 Kellogg–Briand Pact, in which several nations (including Japan and the United States) renounced war and promised to peacefully solve disputes. In the aftermath of invasion of Manchuria, Stimson and other members of the Cabinet came to believe that war with Japan might be inevitable, though Hoover continued to push for disarmament among the world powers.