The 1955 military alliance that united the Soviet Union and its Eastern Bloc allies was the Warsaw Pact.
Formally called the Treaty of Friendship, Cooperation and Mutual Assistance, it was signed in Warsaw on 14 May 1955. The Soviet Union joined Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania as founding members. Its creation followed West Germany’s admission to NATO and formalized Moscow’s military ties with its satellite states.
The Warsaw Pact was commonly portrayed as the Eastern Bloc counterpart to NATO. The alliance coordinated military planning and placed its armed forces under a Soviet-led command, although member states did not always share Moscow’s policies. Romania maintained a degree of independence, while Albania withdrew after the Soviet-Albanian split.
A common mix-up is confusing the Warsaw Pact with Comecon, which was the Eastern Bloc’s economic organization. The Pact’s most significant military actions were interventions inside its own bloc, including the 1968 invasion of Czechoslovakia. It was dissolved in 1991, shortly before the Soviet Union itself collapsed.