Đức was promoted to major general in 1956 and served as an officer in the Airborne Brigade. He was sent abroad to act as the ambassador to South Korea from 1956 to 1957. Đức was regarded as an effective but idiosyncratic officer. During the later years of Diệm's rule, Đức was in exile in France. The arrest and assassination of Diệm after a November 1963 coup allowed Đức a chance to return to Vietnam.