 Before he joined the Communists, Lü worked as an assistant to the Kuomintang general, Zhang Xueliang.It was in this role that he was a witness to the Xi'an Incident, whereby Zhang and his fellow general, Yang Hucheng, forced the then-Chinese leader, Chiang Kai-shek to suspend the civil war with the Communists in 1936 in order and join forces against the Japanese.Lü resigned from the Kuomintang in 1937 and joined the Communist Party.