The Brezhnev Doctrine was a policy promoted in 1968 by Soviet leader Leonid Brezhnev. It said that the Soviet Union had the right to use military force to maintain the strict rule of the Communist Party in nearby socialist countries. The Brezhnev Doctrine was used to justify the invasion of Czechoslovakia, earlier in 1968 after Alexander Dubček introduced political reforms there. The principles of the doctrine were so broad that the Soviets used it to justify intervention in the non-Warsaw Pact nation of Afghanistan in 1979, starting the Soviet war in Afghanistan. The Brezhnev Doctrine stayed in effect until it was ended with the Soviet reaction to the Polish crisis of 1980–1981.