 Serong was appointed to command the Australian Army Training Team Vietnam (AATTV) in 1962.He was later seconded to the Americans and was senior advisor to the South Vietnamese Police Field Force between 1965 and 1968.Leaving the army in 1968, he remained in Vietnam as a security and intelligence adviser to the South Vietnamese government, as well as working for the Rand organisation, Hudson Institute and other corporations, and consulting to the Pentagon and several US presidents.