 That month, the Lithuanian Supreme Soviet ruled the 1940 Soviet annexation of their country to be illegal; in January 1990, Gorbachev visited the republic to encourage it to remain part of the Soviet Union.Gorbachev rejected the "Brezhnev Doctrine", the idea that the Soviet Union had the right to intervene militarily in other Marxist-Leninist countries if their governments were threatened.In December 1987 he announced the withdrawal of 500,000 Soviet troops from Central and Eastern Europe.