In June, 1956, a revolt against Soviet influence in Poland was defeated by the Polish army, but the Poles managed to gain some concessions from Moscow; an uprising in Hungary in Oct., 1956, was crushed ruthlessly by Soviet troops.
In the technological race between the Soviet Union and the West (principally the United States), the USSR exploded (1953) a hydrogen bomb; announced (1957) the development of intercontinental ballistic missiles; orbited (1957) the first artificial earth satellite (called Sputnik); and in 1961 sent Yuri Gagarin in the first manned orbital flight.
Brezhnev died in 1982 and was replaced by Yuri Andropov, the recent head of the KGB.