Video: 'Vietnam: The Ten Thousand Day War - The Village War [10/13]' (Cambodia Campaign at 33:17)

(Friday, May 1, 1970, 7:30 a.m. Saigon Standard Time; during the Cambodian Campaign, part of the Vietnam War, Cambodian Civil War, Indochina Wars and the Cold War) — Several thousand U.S. soldiers moved across the border from South Vietnam to Cambodia’s Kampong Cham Province this morning, expanding the American involvement in the Vietnam War to attack North Vietnamese Army (NVA) enclaves in an area known as the Fishhook.

Helicopters and ground troops of the U.S. Army’s 1st Air Cavalry Division and an airborne brigade of South Vietnam’s Army of the Republic of Vietnam (ARVN) caught the NVA off guard, while troops of the 25th Infantry Division drove their attack northward and westward; by May 3, the United States would claim 467 of the enemy had been killed, and only eight American soldiers.

Video: 'The Sensational 70s - 1970' (Cambodia Campaign at 16:54)

Simultaneously with the invasion, U.S. President Richard Nixon was preparing to announce the invasion in a nationwide address, which would begin Thursday, Apr. 30, 1970, at 9:00 p.m. EDT in Washington, D.C.

Protests against the expansion of the Vietnam War began on American college campuses later in the day on Friday.

For the first time in more than 50 years, the U.S. Senate Foreign Relations Committee voted to ask for a meeting with a U.S. President, after having been given no notice of the invasion, and the request was unanimous from both political parties.