The
Space Race was a 20th-century competition between two
Cold War rivals, the
Soviet Union (USSR) and the
United States (US), for supremacy in
spaceflight capability. It had its origins in the
missile-based
nuclear arms race between the two nations that occurred following World War II, enabled by captured
German rocket technology and personnel. The technological superiority required for such supremacy was seen as necessary for national security, and symbolic of ideological superiority. The Space Race spawned pioneering efforts to launch
artificial satellites, unmanned
space probes of the
Moon,
Venus, and
Mars, and
human spaceflight in
low Earth orbit and to the Moon. The competition began on August 2, 1955, when the Soviet Union responded to the US announcement four days earlier of intent to launch artificial satellites for the
International Geophysical Year, by declaring they would also launch a satellite "in the near future". The Soviet Union beat the US to this, with the October 4, 1957 orbiting of
Sputnik 1, and later beat the US to the first human in space,
Yuri Gagarin, on April 12, 1961. The Space Race peaked with the July 20, 1969 US landing of the first humans on the Moon with
Apollo 11. The USSR tried but failed manned lunar missions, and eventually cancelled them and concentrated on Earth orbital space stations. A period of
détente followed with the April 1972 agreement on a co-operative
Apollo–Soyuz Test Project, resulting in the July 1975 rendezvous in Earth orbit of a US astronaut crew with a Soviet cosmonaut crew.