tet offensive

noun

1. an offensive by Vietcong and North Vietnamese forces against South Vietnamese and U.S. positions in South Vietnam, beginning on Jan. 31, 1968, the start of Tet.

A series of major attacks by communist forces in the Vietnam War. Early in 1968, Vietnamese communist troops seized and briefly held some major cities at the time of the lunar new year, or Tet. The Tet offensive, a turning point in the war, damaged the hopes of United States officials that the combined forces of the United States and South Vietnam could win.