Short answers, pulled from the story.
The term Soviet empire emerged during the late 1950s to describe a specific pattern of global dominance. Richard Pipes published his book The Formation of the Soviet Union: Communism and Nationalism, 1917, 1923 in 1957 marking a key moment when scholars began analyzing the USSR as an imperial entity rather than just a socialist state.
Member states included Poland Bulgaria Czechoslovakia East Germany Hungary Romania and Albania until 1968. These countries were occupied or formerly occupied by the Red Army during World War II and their politics military foreign and domestic policies remained dominated by the Soviet Union throughout the Cold War.
Countries such as Cuba Vietnam Angola Ethiopia and Mozambique received substantial aid either military or economic from Moscow. Indonesia enjoyed Soviet backing between 1959 and 1965 before relations deteriorated while Libya maintained ties with the USSR from 1969 to 1991.
Joseph Stalin ordered deportations of entire nationalities to remote underpopulated areas during the 1930s through the 1950s. Ethnic Russians and Ukrainians often replaced deported populations in Central Asian territories like Kyrgyzstan and the policy officially ended in the Khrushchev era allowing some nationalities to return by 1957.
The interventionist Brezhnev Doctrine permitted invasion of countries deemed inconsistent with socialist ideology. This framework allowed leaders to signal toleration or disapproval indirectly through ideological declarations recreating a hegemonic role without direct annexation.