The first members of the Warsaw Pact were the Soviet Union, Albania, Bulgaria, Czechoslovakia, the GDR, Hungary, Poland and Romania. Yugoslavia was the only communist state not to have signed the treaty. Albania withdrew from the pact in 1968. Although the pact was originally created to counter the threat posed by NATO, in practice it was a tool of the Soviet Union that allowed it to strengthen its influence over its satellite countries. Unlike NATO, the Warsaw Pact was completely subordinate to a single power. The pact allowed the Soviet Union to impose its military and political agenda on the countries of Central and Eastern Europe through the use of their military and economic power. The pact was to last only twenty years and become invalid if one of the members decided to withdraw.