 U.S. Army General William C. Westmoreland served four years in Vietnam, from 1964 to 1968, as COMUSMACV—Commander U.S. Military Assistance Command Vietnam.He was in command during the Tet Offensive, a surprise, country-wide attack on the U.S. forces by the combined forces of the National Front for the Liberation of South Vietnam and the Vietnam People's Army in 1968.The attack is widely viewed as having contributed to a growing perception in the United States that the U.S. had underestimated enemy strength and resolve, and that, in contrast to assurances from Westmoreland and the Johnson administration, there was no "light at the end of the tunnel."