He worked as a miner at Anyuan Coal Mine near Pingxiang at the age of 16 (1926) and may have heard Mao Zedong speak during the 1927 strike organization efforts.

In August 1946, Yang and Xiao Ke retreated in the face of an onslaught by three reinforced Nationalist corps concentrated on the rail lines between Beiping and Shenyang.

In April 1948, Yang commanded the 2nd Army (later redesignated the 19th) under the North China Military Region of Nie Rongzhen and Xu Xiangqian.

The outbreak of hostilities on the Korean peninsula led to Yang's 19th Army being pre-positioned in Shandong, where it was re-equipped with new Russian arms.

Yang's forces participated in the fifth offensive against the ROK 1st Division and British 29th Brigade, destroying the Gloucester Battalion during the push toward Seoul.

In May 1952, his forces were driven back from Chorwon and, suffering heavy casualties withdrew north for reinforcements from Yang Chengwu's 20th Army.

[8] Yang took over from Deng Xiaoping as PLA Chief-of-Staff in February 1980, joined the standing committee of the CCP Military Affairs Commission and was named a Vice Minister of National Defense a month later.

During the Tiananmen Square protests of spring 1989, Yang Dezhi joined former Minister of Defense Zhang Aiping and five other retired generals in opposing the enforcement of martial law by the Army in Beijing.