On January 30, 1968, the North Vietnamese launched simultaneous attacks on almost every major city in South Vietnam. These attacks, which came to be known as the Tet Offensive, were planned to coincide with Tet Nguyen Dan, the lunar new year festival, one of the most important Vietnamese holidays. North Vietnamese forces briefly took control of several important cities during the Tet Offensive. In fact, the worst single massacre of the Vietnam War took place during the temporary Communist occupation of Hue, when 3,000 civilians were brutally murdered and buried in a mass grave. South Vietnamese and U.S. forces were quick to characterize the Tet Offensive as a failure since all North Vietnamese gains made during the attack were eventually reversed, but it was a major psychological victory for the North which had previously been characterized as being on the verge of collapse. The American people, many of which were beginning to question the wisdom of this war, could no longer be convinced that there was a light swiftly approaching at the end of the tunnel.