Operation Barrel Roll, a covert American bombing campaign in Laos to stop communist infiltration of South Vietnam, ends.

Operation Barrel Roll was a covert interdiction and close air support campaign conducted in the Kingdom of Laos by the U.S. Air Force 2nd Air Division and U.S. Navy Task Force 77 between 5 March 1964 and 29 March 1973, concurrent with the Vietnam War.

Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and southwest. The country has a population of approximately eight million. Its capital and most populous city is Vientiane. The country has Buddhist temples, including the UNESCO's World Heritage Site of Luang Prabang, and French colonial architecture.

The People's Army of Vietnam (PAVN), officially the Vietnam People's Army, also recognized as the Vietnamese Army, the People's Army or colloquially the Troops, is the national military force of the Socialist Republic of Vietnam and the armed wing of the ruling Communist Party of Vietnam (CPV). The PAVN is the backbone component of the Vietnam People's Armed Forces and includes: Ground Force, Navy, Air Force, Border Guard and Coast Guard. Vietnam does not have a separate and formally-structured Ground Force or Army service. Instead, all ground troops, army corps, military districts and special forces are designated under the umbrella term combined arms and belong to the Ministry of National Defence, directly under the command of the CPV Central Military Commission, the Minister of National Defence, and the General Staff of the Vietnam People's Army. The military flag of the PAVN is the National flag of the Socialist Republic of Vietnam defaced with the motto Quyết thắng added in yellow at the canton.

South Vietnam, officially the Republic of Vietnam, was a country in Southeast Asia that existed from 1955 to 1975. It first garnered international recognition in 1949 as the associated State of Vietnam within the French Union, with its capital at Saigon. Since 1950, it was a member of the Western Bloc during the Cold War. Following the 1954 partition of Vietnam, it became known as South Vietnam and was established as a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957. It was succeeded by the Republic of South Vietnam in 1975. In 1976, the Republic of South Vietnam and North Vietnam merged to form the Socialist Republic of Vietnam.