The Tet Offensive was one of the largest military campaigns of the Vietnam War, launched on January 30, 1968 by forces of the Viet Cong and North Vietnamese Army against the forces of South Vietnam, the United States, and their allies. It was a campaign of surprise attacks against military and civilian commands and control centers throughout South Vietnam.
The communists launched a wave of attacks in the late night hours of 30 January in the I and II Corps Tactical Zones of South Vietnam. This early attack did not lead to widespread defensive measures. When the main communist operation began the next morning the offensive was countrywide and well coordinated, eventually more than 80,000 communist troops striking more than 100 towns and cities, including 36 of 44 provincial capitals, five of the six autonomous cities, 72 of 245 district towns, and the southern capital. The offensive was the largest military operation conducted by either side up to that point in the war.
The initial attacks stunned the US and South Vietnamese armies and caused them to temporarily lose control of several cities, but they quickly regrouped to beat back the attacks, inflicting massive casualties on communist forces. During the Battle of Huế, intense fighting lasted for a month resulting in the destruction of the city by US forces. During their occupation, the communists executed thousands of people in the Massacre at Huế. Around the US combat base at Khe Sanh fighting continued for two more months. Although the offensive was a military defeat for the communists, it had a profound effect on the US government and shocked the US public, which had been led to believe by its political and military leaders that the communists were, due to previous defeats, incapable of launching such a massive effort.
The term “Tet offensive” usually refers to the January–February 1968 offensive, but it can also include the so-called “Mini-Tet” offensives that took place in May and August.