The Warsaw Pact was established as a balance of power or counterweight to NATO; there was no direct confrontation between them. Instead, the conflict was fought on an ideological basis and in proxy wars. Both NATO and the Warsaw Pact led to the expansion of military forces and their integration into the respective blocs. Its largest military engagement was the Warsaw Pact invasion of Czechoslovakia in August 1968 (with the participation of all Pact nations except Albania, Romania and East Germany), which, in part, resulted in Albania withdrawing from the pact less than a month later. The Pact began to unravel in its entirety with the spread of the Revolutions of 1989 through the Eastern Bloc, beginning with the Solidarity movement in Poland and its electoral success in June 1989.
East Germany withdrew from the Pact following reunification with West Germany in 1990. On 25 February 1991, the Pact was declared at an end at a meeting of defence and foreign ministers from the six remaining member states in Hungary. The USSR itself was dissolved in December 1991, although most of the former Soviet republics formed the Collective Security Treaty Organization shortly thereafter. Throughout the following 20 years, the seven Warsaw Pact countries outside the USSR each joined NATO (East Germany through its reunification with West Germany; and the Czech Republic and Slovakia as separate countries).
In the Western Bloc, the Warsaw Treaty Organization of Friendship, Cooperation and Mutual Assistance is often called the Warsaw Pact military alliance—abbreviated WAPA, Warpac and WP. Elsewhere, in the former member states, the Warsaw Treaty is known as:
The Warsaw Treaty's organization was two-fold: the Political Consultative Committee handled political matters, and the Combined Command of Pact Armed Forces controlled the assigned multi-national forces, with headquarters in Warsaw, Poland. Furthermore, the Supreme Commander of the Unified Armed Forces of the Warsaw Treaty Organization which commanded and controlled all the military forces of the member countries was also a First Deputy Minister of Defence of the USSR, and the Chief of Combined Staff of the Unified Armed Forces of the Warsaw Treaty Organization was also a First Deputy Chief of the General Staff of the Armed Forces of the USSR. Therefore, although ostensibly an international collective security alliance, the USSR dominated the Warsaw Treaty armed forces.
The strategy behind the formation of the Warsaw Pact was driven by the desire of the Soviet Union to dominate Central and Eastern Europe. The Soviets wanted to keep their part of Europe theirs and not let the Americans take it from them. This policy was driven by ideological and geostrategic reasons. Ideologically, the Soviet Union arrogated the right to define socialism and communism and act as the leader of the global socialist movement. A corollary to this idea was the necessity of intervention if a country appeared to be violating core socialist ideas and Communist Party functions, which was explicitly stated in the Brezhnev Doctrine. Geostrategic principles also drove the Soviet Union with the desire to create a buffer zone to prevent invasion of its territory by Western European powers.