Eastern Bloc

Eastern Bloc was the name used by NATO-affiliated countries for the former communist states of Central and Eastern Europe, generally the Soviet Union and the countries of the Warsaw Pact. The terms Communist Bloc and Soviet Bloc were also used to denote groupings of states aligned with the Soviet Union, although these terms might include states outside Central and Eastern Europe.

The USSR and World War II in Central and Eastern Europe

In 1922, the RSFSR, the Ukrainian SSR, the Byelorussian SSR and the Transcaucasian SFSR, approved the Treaty of Creation of the USSR and the Declaration of the Creation of the USSR, forming the Soviet Union. Soviet leader Joseph Stalin, who viewed the Soviet Union as a "socialist island", stated that the Soviet Union must see that "the present capitalist encirclement is replaced by a socialist encirclement."

Expansion of the USSR in 1939–1940

In 1939, the USSR entered into the Molotov–Ribbentrop Pact with Nazi Germany that contained a secret protocol that divided Romania, Poland, Lithuania, Estonia and Finland into German and Soviet spheres of influence. Eastern Poland, Latvia, Estonia, Finland and Bessarabia in northern Romania were recognized as parts of the Soviet sphere of influence. Lithuania was added in a second secret protocol in September 1939.