 Hưng was perhaps best known as the "Hero of An Lộc" in 1972 when he commanded the 5th Division in defense of the city of An Lộc from the coordinated attacks of the North Vietnamese People's Army of Vietnam (PAVN) forces in the Battle of An Lộc.In April 1971 Hưng was appointed to take over the battered 5th Division from General Nguyễn Văn Hiếu.General Hiếu's forces had been badly handled during the Battle of Snuol, and his troops, according to II Field Force, Vietnam commander Michael S. Davison, were close to mutiny.