Under the Soviet Union, Stalin did indeed take over many countries including those you mentioned. Here is some more info:

- 1934: Invasion of Xinjiang (China), which led to heavy casualties on both sides
- 1939 (1 Sept to 6 Oct): Invasion of Poland, a brutal invasion coordinated by the Soviet Union and Germany which led to significant loss of life particularly for Poland (66,000 killed, 133,700 wounded, and ~675,000 captured). For more info, see https://en.wikipedia.org/wiki/Invasion_of_Poland 
- 1939-1940: The Soviet union invaded Finland and as a result of this and other actions was kicked out of the League of Nations. In the end, they got ~11% of Finnish territory
- 1939-1945: During World War II, the Soviet Union additionally completely or partially occupied Romania, Bulgaria, Hungary, Yugoslavia, Czechoslovakia, Austria, Denmark, and Norway

Although Soviets and Germany cooperated for some time, this fell through and eventually Germany attempted and failed to invade the Soviet Union. 

Stalin was ultimately found dead on March 1, 1953, and the Soviet Union was dissolved in 1991.

Sources:
- https://en.wikipedia.org/wiki/Foreign_interventions_by_the_Soviet_Union
- https://en.wikipedia.org/wiki/History_of_the_Soviet_Union_(1927%E2%80%931953)
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