Learn how to say Tet correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word Tet Offensive:
(in the Vietnam War) an offensive launched in January-February 1968 by the Vietcong and the North Vietnamese army. Timed to coincide with the first day of the Tet (Vietnamese New Year), it was a surprise attack on South Vietnamese cities, notably Saigon. Although repulsed after initial successes, the attack shook US confidence and hastened the withdrawal of its forces.