Yang had a long and eventful military career, serving as both battlefield commander and political commissar. He fought in the Second Sino–Japanese War and subsequently in the Chinese Civil War, which led to the victory of the CPC and the establishment of the People's Republic of China in 1949. From 1949 until 1966 and the outbreak of the Cultural Revolution, Yang continuously served in the Southwest, and took part in the invasion and conquest of Tibet in 1950–51, as well as the crushing of the 1959 Tibetan Rebellion. In 1960 he became Deputy Director, and in 1964 Director, of the Political Department of the Chengdu Military Region.