The construction of the Forbidden City started in 1406 and took 14 years and an estimated 200,000 men. From its completion in 1420 to 1644, when a peasant revolt led by Li Zicheng invaded it, the Forbidden City served as the seat of the Ming Dynasty. The following Qing Dynasty also occupied the Forbidden City. In 1860, during the Second Anglo-Chinese Opium War, British forces managed to penetrate to the heart of the Forbidden City and occupied it until the end of the war, being the only foreign power to do so. After being the home of 24 emperors—fourteen of the Ming Dynasty and ten of the Qing Dynasty—the Forbidden City ceased being the political center of China in 1912 with the abdication of Pu Yi, the last Emperor of China.