In late January, 1968, during the lunar new year (or “Tet”) holiday, North Vietnamese and communist Viet Cong forces launched a coordinated attack against a number of targets in South Vietnam.The U.S. and South Vietnamese militaries sustained heavy losses before finally repelling the communist assault.The Tet Offensive played an important role in weakening U.S. public support for the war in Vietnam.he U.S. and South Vietnamese militaries sustained heavy losses before finally repelling the communist assault. The Tet Offensive played an important role in weakening U.S. public support for the war in Vietnam.