Bell UH-1 Iroquois in the context of "U.S. involvement in the Vietnam War"

Agent Orange is a chemical herbicide and defoliant, one of the tactical uses of Rainbow Herbicides. It was used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1962 to 1971. The U.S. was strongly influenced by the British who used Agent Orange during the Malayan Emergency. It is a mixture of equal parts of two herbicides, 2,4,5-T and 2,4-D.

Agent Orange was produced in the United States beginning in the late 1940s and was used in industrial agriculture, and was also sprayed along railroads and power lines to control undergrowth in forests. During the Vietnam War, the U.S. military procured over 20,000,000 U.S. gal (76,000,000 L; 17,000,000 imp gal), consisting of a fifty-fifty mixture of 2,4-D and dioxin-contaminated 2,4,5-T. Nine chemical companies produced it: Dow Chemical Company, Monsanto Company, Diamond Shamrock Corporation, Hercules Inc., Thompson Hayward Chemical Co., United States Rubber Company (Uniroyal), Thompson Chemical Co., Hoffman-Taff Chemicals, Inc., and Agriselect.

The involvement of the United States in the Vietnam War began in the 1950s and greatly escalated in 1965 until its withdrawal in 1973. The U.S. military presence in Vietnam peaked in April 1969, with 543,000 military personnel stationed in the country. By the end of the U.S. involvement, more than 3.1 million Americans had been stationed in Vietnam, and 58,279 had been killed.

After World War II ended in 1945, President Harry S. Truman declared his doctrine of "containment" of communism in 1947 at the start of the Cold War. U.S. involvement in Vietnam began in 1950, with Truman sending military advisors to assist the French Union against Viet Minh rebels in the First Indochina War. The French withdrew in 1954, leaving North Vietnam in control of the country's northern half. President Dwight D. Eisenhower ordered covert CIA activities in South Vietnam. Opposition to the regime of Ngo Dinh Diem in South Vietnam was quashed with U.S. help, but from 1957 insurgents known as the Viet Cong launched a campaign against the state. North Vietnam supported the Viet Cong, which began fighting the South Vietnamese army. President John F. Kennedy, who subscribed to the "domino theory" that communism would spread to other countries if Vietnam fell, expanded U.S. aid to South Vietnam, increasing the number of advisors from 900 to 16,300, but this failed to produce results. In 1963, Diem was deposed and killed in a military coup tacitly approved by the U.S. North Vietnam began sending detachments of its own army, armed with Soviet and Chinese weapons, to assist the Viet Cong.

The Sikorsky UH-60 Black Hawk is a four-blade, twin-engine, medium-lift military utility helicopter manufactured by Sikorsky Aircraft. Sikorsky submitted a design for the United States Army's Utility Tactical Transport Aircraft System (UTTAS) competition in 1972. The Army designated the prototype as the YUH-60A and selected the Black Hawk as the winner of the program in 1976, after a fly-off competition with the Boeing Vertol YUH-61.

Named after the Native American war chief Black Hawk, the UH-60A entered service with the U.S. Army in 1979, to replace the Bell UH-1 Iroquois as the Army's tactical transport helicopter. This was followed by the fielding of electronic warfare and special operations variants of the Black Hawk. Improved UH-60L and UH-60M utility variants have also been developed.