1. The Tet Offensive (January–March 1968): This was a massive surprise attack by the Viet Cong and North Vietnamese forces on over 100 cities and military installations in South Vietnam. Although it was ultimately a military defeat for the communists, the Tet Offensive had a profound impact on American public opinion. It shattered the Johnson administration's claims that the war was winding down and that victory was imminent, and it led many Americans to question the wisdom of continuing the war.
2. The My Lai Massacre (March 1968): This was the brutal massacre of over 500 unarmed Vietnamese civilians by American soldiers in the village of My Lai. The massacre was exposed by the media, and it further eroded public support for the war.
3. The Kent State Shootings (May 1970): This was the killing of four unarmed Kent State University students by Ohio National Guardsmen during an anti-war protest. The shootings were captured on film and broadcast on national television, and they sparked outrage and protests across the country. The Kent State Shootings further deepened the divisions in American society over the war and contributed to the decline of public support for the war.