The Space Race was a 20th-century competition between two Cold War rivals, the USSR and the  US, to achieve firsts in spaceflight capability. It had its origins in the ballistic missile-based nuclear arm race between the two nations that occurred following WWII. The technological advantage required to rapidly achieve spaceflight milestones was seen as necessary for national security and mixed with the symbolism and ideology of the time. The Space Race led to pioneering efforts to launch artificial satellites, uncrewed space probes of the Moon, Venus and Mars, and human spaceflight in low Earth orbit and to the Moon.