Which major offensive in 1968 turned American public opinion against the war?

The major 1968 offensive that helped turn American public opinion against the war was the Tet Offensive. It began during Tet, the Vietnamese Lunar New Year, when North Vietnamese and Viet Cong forces launched coordinated attacks across South Vietnam.

The offensive started on January 30–31, 1968, striking cities, towns, military bases, and government facilities. Communist forces even attacked the US Embassy compound in Saigon, an event that became a powerful television image for Americans. Although US and South Vietnamese forces eventually retook the contested areas and inflicted severe losses on the attackers, the offensive had an enormous political and psychological impact.

Before Tet, US officials had often presented the war as being steadily brought under control. The scale and coordination of the attacks made that claim appear unreliable, even though the offensive was a battlefield defeat for North Vietnam and the Viet Cong in many locations. News coverage and public debate increasingly focused on whether victory was possible at an acceptable cost.

The Tet Offensive contributed to President Lyndon B. Johnson's declining approval, his decision not to seek another presidential term, and later efforts to reduce direct US involvement. It did not instantly end American support for the war, but it became a decisive turning point in perceptions of the conflict.