Japanese forces attacked Shanghai in January 1932 on the pretext of Chinese resistance in Manchuria. Finding stiff Chinese resistance in Shanghai, the Japanese waged a three-month undeclared war there before a truce was reached in March 1932. Several days later, Manchukuo was established. Manchukuo was a Japanese puppet state headed by the last Chinese emperor, Puyi, as chief executive and later emperor. The civilian government in Tokyo was powerless to prevent these military happenings. Instead of being condemned, the Guandong Army's actions enjoyed popular support back home. International reactions were extremely negative, however. Japan withdrew from the League of Nations, and the United States became increasingly hostile.