In 1955, the Soviet Union and its Eastern Bloc allies signed a security pact in the Polish capital, Warsaw, in response to further expansion of NATO by the West. It was known as the "Warsaw Pact" and was intended to strengthen military, economic and cultural ties between the eight Communist nations. The pact allowed the USSR to suppress nationalist uprisings in member states which led to its military forces crushing rebellions in Hungary in 1956 and Czechoslovakia in 1968. The Warsaw Pact was formally ended in 1991.