The Tet Offensive was a major escalation and one of the largest military campaigns of the Vietnam War. The North Vietnamese People's Army of Vietnam (PAVN) and its Viet Cong (VC) launched a surprise attack on 30 and 31 January 1968 against the forces of the South Vietnamese Army of the Republic of Vietnam (ARVN), the United States Armed Forces and their allies. The offensive launched surprise attacks against military and civilian command and control centers throughout South Vietnam. The name is the truncated version of the Lunar New Year festival name in Vietnamese, Tết Nguyên Đán, a holiday period when most ARVN personnel were on leave. The purpose of the wide-scale offensive by the Le Duan's Politburo was to trigger political instability in a belief that a mass armed assault on urban centers would trigger defections and uprisings.

The offensive was launched prematurely in the early morning hours of 30 January in large parts of the I and II Corps Tactical Zones of South Vietnam. This early attack allowed allied forces some time to prepare defensive measures. When the main operation began during the early morning of 31 January, the offensive was countrywide; 77,000 PAVN/VC troops struck more than 100 towns and cities, including 36 of 44 provincial capitals, 5 of 6 autonomous cities, 72 of 245 district towns, and the capital Saigon. The offensive was the largest military operation conducted by either side by that point in the war.

The US/South Vietnam:

1st Huê.

2nd Saigon.

3rd Khe Sanh.

4th Da Nang.

5th Long Bihn.