Apollo–Soyuz was the first crewed international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo spacecraft docked with a Soviet Soyuz capsule. The project, and its handshake in space, was a symbol of détente between the two superpowers during the Cold War. The mission was officially known as the Apollo–Soyuz Test Project (ASTP; , and commonly referred to in the Soviet Union as Soyuz–Apollo; the Soviets officially designated the mission as Soyuz 19). The unnumbered American vehicle was left over from the canceled Apollo missions, and was the last Apollo module to fly. The three American astronauts, Thomas P. Stafford, Vance D. Brand, and Deke Slayton, and two Soviet cosmonauts, Alexei Leonov and Valeri Kubasov, performed both joint and separate scientific experiments, including an arranged eclipse of the Sun by the Apollo module to allow instruments on the Soyuz to take photographs of the solar corona. The pre-flight work provided useful engineering experience for later joint American–Russian space flights, such as the Shuttle–Mir program and the International Space Station. Apollo–Soyuz was the last crewed United States spaceflight for nearly six years until the first launch of the Space Shuttle on 12 April 1981, and the last crewed United States spaceflight in a space capsule until Crew Dragon Demo-2 on 30 May 2020. Historical background The purpose and catalyst of Apollo–Soyuz was the policy of détente between the two Cold War superpowers: the United States and the Soviet Union. Tensions ran high between the two world superpowers while the United States was engaged in the Vietnam War. Meanwhile, the Soviet press was highly critical of the Apollo space missions, printing "the armed intrusion of the United States and Saigon puppets into Laos is a shameless trampling underfoot of international law" over a photograph of the Apollo 14 launch in 1971. Although Soviet leader Nikita Khrushchev made the Soviet Union's policy of détente official in his 1956 doctrine of peaceful coexistence at the 20th Congress of the Communist Party of the Soviet Union, the two nations seemed to be in perpetual conflict. After John Glenn's 1962 orbital flight, an exchange of letters between President John F. Kennedy and Soviet Premier Nikita Khrushchev led to a series of discussions led by NASA Deputy Administrator Hugh Dryden and Soviet scientist Anatoly Blagonravov. Their