1955    Cold War: Eight communist bloc countries, including the Soviet Union, sign a mutual defense treaty called the Warsaw Pact.

1968    Soviet Union-dominated Warsaw Pact troops invade Czechoslovakia, crushing the Prague Spring; on the same day, Nicolae Ceauşescu, leader of Communist Romania, publicly condemns the Soviet maneuver, encouraging the Romanian population to arm itself against possible Soviet reprisals.

1968    Albania leaves the Warsaw Pact.

1991    The Warsaw Pact is officially dissolved at a meeting in Prague.

1999    Former Warsaw Pact members the Czech Republic, Hungary and Poland join NATO.

2005    Polish Minister of National Defence Radek Sikorski opens Warsaw Pact archives to historians. Maps of possible nuclear strikes against Western Europe, as well as the possible nuclear annihilation of 43 Polish cities and 2 million of its citizens by Soviet-controlled forces, are released.