The Warsaw Pact was established as a balance of power or counterweight to NATO. There was no direct military 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 and Romania), 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, its electoral success in June 1989 and the Pan-European Picnic in August 1989.