On May 15, 1955, representatives of the Soviet Union, Albania, Bulgaria, Czechoslovakia, Hungary, Poland, and Romania meeting in Warsaw, Poland, signed the multilateral Treaty on Friendship, Cooperation, and Mutual Assistance, officially designated the "Pact of Mutual Assistance and Unified Command," and more popularly known as the Warsaw Pact.
The alliance was to act as:
a Soviet counterbalance to NATO in East-West diplomacy,
a method to legitimize the Soviet presence in Eastern European countries where treaties with the Soviets had already been established, and
a mechanism to convey U.S.S.R. defense and foreign policy directives to its Eastern European allies.
The treaty specified that relations among the member countries would consist of mutual noninterference in domestic matters, and respect for the sovereignty and independence of each country, and provided a collective defense unit against possible aggressors to communist governance. The Soviet Union's vested interest was to protect itself from western aggressors, using East European governments as a buffer, and use its Red Army to uphold communist rule in those countries.
During General Secretary Nikita Khrushchev
's destalinization* of the U.S.S.R. following Stalin's death in 1953, he permitted the restoration of distinct national practices and military training for each member country's soldiers as the primary modi operandi
of Eastern European military establishments. In addition, he allowed the removal of many Soviet Army officers and advisors from key Eastern European armies.
However, the iron fist within the velvet glove became evident when the Warsaw Pact was invoked as the justification for comradely intervention in Hungary in 1956 and Czechoslovakia in 1967.
Following the collapse of communism in Eastern Europe, the Warsaw Pact was dissolved on July 1, 1991. The Soviet Union itself wad dissolved before the end of the year.
*In the course of denouncing Joseph Stalin at a public meeting one day, Nikita Khrushchev was interrupted by a voice from the audience: "You were one of Stalin's colleagues," the heckler declared. "Why didn't you stop him?"
"Who said that!?" Khrushchev roared. The room was quickly filled with an agonizing silence — finally broken by Khrushchev himself. "Now," he remarked in a quiet voice, "you know why." (anecdote.com)