In antiquity, Sichuan was the home of the ancient states of Ba and Shu. Their conquest by Qin strengthened it and paved the way for the Qin Shi Huang's unification of China under the Qin dynasty. During the Three Kingdoms era, Liu Bei's Shu was based in Sichuan. The area was devastated in the 17th century by Zhang Xianzhong's rebellion and the area's subsequent Manchu conquest, but recovered to become one of China's most productive areas by the 19th century. During World War II, Chongqing served as the temporary capital of the Republic of China, making it the focus of Japanese bombing. It was one of the last mainland areas captured by the People's Liberation Army during the Chinese Civil War and was divided into four parts from 1949 to 1952, with Chongqing restored two years later. It suffered gravely during the Great Chinese Famine of 1959–61 but remained China's most populous province until Chongqing Municipality was again separated from it in 1997.