The Tet Offensive was a major military campaign during the Vietnam War that began on January 30, 1968, when North Vietnamese and Viet Cong forces launched a surprise attack on South Vietnam during the Vietnamese Lunar New Year, known as Tet. This offensive marked a pivotal moment in the conflict as it significantly shifted public perception of the war in the United States and highlighted the resilience and strength of communist forces in Vietnam, challenging the prevailing belief that the U.S. was winning the war.