 Complete the following phrase:  Between 1947 and September 22, 1949, Pengs forces occupied Gansu, Ningxia, and Qinghai. His forces repeatedly defeated but could not destroy the forces of Hu Zong and Ma Bufang, which retreated into Sichuan and were airlifted to Taiwan when the Kuomintang lost the Civil War in December 1949. In October Pengs forces, led directly by Wang Zhen, invaded Xinjiang. Most of Xinjiangs defenders 