Vietnam War: US President Richard Nixon formally authorizes American combat troops to take part in the Cambodian campaign.

The Vietnam War was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam and South Vietnam and their allies. North Vietnam was supported by the Soviet Union and China, while South Vietnam was supported by the United States and other anti-communist nations. The conflict was the second of the Indochina wars and a proxy war of the Cold War between the Soviet Union and US. The Vietnam War was one of the postcolonial wars of national liberation, a theater in the Cold War, and a civil war, with civil warfare a defining feature from the outset. Direct US military involvement escalated from 1965 until its withdrawal in 1973. The fighting spilled into the Laotian and Cambodian Civil Wars, which ended with all three countries becoming communist in 1975.

Richard Milhous Nixon was the 37th president of the United States, serving from 1969 until his resignation in 1974. A member of the Republican Party, he represented California in both houses of the United States Congress before serving as the 36th vice president under President Dwight D. Eisenhower from 1953 to 1961. His presidency saw the reduction of U.S. involvement in the Vietnam War, détente with the Soviet Union and China, the Apollo 11 Moon landing, and the establishment of the Environmental Protection Agency and Occupational Safety and Health Administration. Nixon's second term ended early when he became the only U.S. president to resign from office, as a result of the Watergate scandal.

The Cambodian campaign was a series of military operations conducted in eastern Cambodia in mid-1970 by South Vietnam and the United States as an expansion of the Vietnam War and the Cambodian Civil War. Thirteen operations were conducted by the Army of the Republic of Vietnam (ARVN) between April 29 and July 22 and by U.S. forces between May 1 and June 30, 1970.