On December 10, 1949, Chiang Kai-shek evacuated the last KMT-held city on the mainland and completed the Nationalist government's withdrawal to Taiwan. Mao Zedong had proclaimed the People's Republic of China on October 1. Approximately two million military personnel, officials, and civilians crossed to Taiwan, along with China's gold reserves and national treasures. Chiang declared Taipei the temporary capital of the Republic of China and imposed martial law, which remained in force until 1987. The US Seventh Fleet deployed to the Taiwan Strait in June 1950 following the outbreak of the Korean War, preventing PRC invasion.