Answer:
The Tet Offensive, which began on 31 January 1968, was an aggressive military campaign by the North Vietnamese Army and the Vietcong communist forces against South Vietnam and the United States during the Vietnam War. North and South Vietnam declared that they would stop fighting for two days during the Tet festival, which was taking place during those days. On the morning of January 31st the Vietcong launched a series of raids in South Vietnam, and a broader campaign on February 1st targeting more than 100 towns and cities in the South. The Invasion was unexpected by the Southern Vietnamese and American governments.
Although the South Vietnamese and US forces were tactically victorious, their failure to anticipate the Invasion was a political victory for the communists. The Tet Offensive was considered a turning point in the Vietnam War, as from then on US media began to criticize the American participation in the war, and to support the pacifist movements that were looking for an end to the conflict. Finally, as a result of both media and social pressure, America started a process of "Vietnamization", which involved a gradual withdrawal from the war.