General Cao Văn Viên, chief of the South Vietnamese military, departs for the US as the North Vietnamese Army closes in on victory.

Cao Văn Viên was a four-star army general in the Army of the Republic of Vietnam during the Vietnam War. He rose to the position of Chairman of the South Vietnamese Joint General Staff. Considered one of "the most gifted" of South Vietnam's military leaders, he was previously called an "absolute key figure" and one of "the most important Vietnamese military leaders" in the U.S.-led fighting during the Vietnam War. Along with Trần Thiện Khiêm he was one of only two four-star generals in the entire history of South Vietnam.

The Army of the Republic of Vietnam composed the ground forces of the South Vietnamese military from its inception in 1955 to the Fall of Saigon on 30 April 1975. Its predecessor was the ground forces of the Vietnamese National Army, established on 8 December 1950, representing Vietnam to fight in the First Indochina War against the communist Viet Minh rebels. At the ARVN's peak, an estimated 1 in 9 citizens of South Vietnam were enlisted, composed of Regular Forces and the more voluntary Regional Forces and the Popular Force militias. It is estimated to have suffered 1,394,000 casualties during the Vietnam War.

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.