After World War II, emigration restrictions were imposed by countries in the Eastern Bloc, which consisted of the Soviet Union and its satellite states in Central and Eastern Europe. Legal emigration was in most cases only possible to reunite families or to allow members of minority ethnic groups to return to their homelands.

Eastern Bloc governments argued that strict limits to emigration were necessary to prevent a brain drain. The United States and Western European governments argued that they represented a violation of human rights. Despite the restrictions, defections to the West occurred.

After East Germany tightened its zonal occupation border with West Germany, the city sector border between East and West Berlins became a loophole, through which defection could occur. This was closed with the erection of the Berlin Wall in August 1961. Thereafter, emigration from the Eastern Bloc was effectively limited to illegal defections, ethnic emigration under bilateral agreements, and a small number of other cases.

Although the first program of the Bolshevik movement in Russia included a demand for the "abolition of passports", just two months after the Russian Revolution of 1917, the new regime instituted passport controls and forbade the exit of belligerent nationals. The reasoning was partly that emigration was conflated with opposition to the socialist state and also the fear that emigration would inflate opposition armies. The 1918 Treaty of Brest-Litovsk obligated Russia to allow emigration of non-Russians who wanted German citizenship, but the regime attempted to reduce this flow by allowing it during only one month. Beginning in 1919, travel abroad required the approval of the NKVD, with the additional consent of the Special Department of the Cheka added in 1920. In 1922, after the Treaty on the Creation of the USSR, both the Ukrainian SSR and the Russian SFSR issued general rules for travel that foreclosed virtually all departures, making legal emigration all but impossible. However, the Soviet Union could not control its borders until a system of border guards was created through a special corps of the Gosudarstvennoye Politicheskoye Upravlenie (GPU), such that by 1928, even illegal departure was all but impossible.

In 1929 even more strict controls were introduced, decreeing that any Soviet official serving abroad who went over "to the camp of the enemies of the working class and the peasants" and refused to return would be executed within twenty-four hours of being apprehended. In 1932, as Stalin's first Five Year Plan forced collectivization, to allocate scarce housing and weed out "nonproductive" elements, internal passport controls were introduced. When combined with individual city Propiska ("place of residence") permits, and internal freedom of movement restrictions often called the 101st kilometre, these rules greatly restricted mobility within even small areas. When the Soviet Constitution of 1936 was promulgated, virtually no legal emigration took place, except for very limited family reunification and some forced deportations. Very small numbers snuck into Romania, Persia and Manchuria, but the bulk of the population remained essentially captive. Moskovskaya Pravda later described the decision to emigrate as "unnatural and like burying someone alive." Those wishing to leave were viewed not just as deserters, but traitors.

The mobilization of labor in the Soviet Union was not feasible if emigration remained an option with the relative low standard of living that existed at that time. Soviet Premier Nikita Khrushchev later stated "We were scared, really scared. We were afraid the thaw might unleash a flood, which we wouldn't be able to control and which could drown us. How could it drown us? It could have overflowed the banks of the Soviet riverbed and formed a tidal wave that which would have washed away all the barriers and retaining walls of our society."

In addition emigration restrictions were used to keep secrecy about life in the Soviet Union. Starting in 1935, Joseph Stalin had already effectively sealed off outside access to the Soviet Socialist Republics (and until his death in 1953), effectively permitting no foreign travel inside the Soviet Union such that outsiders did not know of the political processes that had taken place therein. During this period, and until the late 1970s, 25 years after Stalin's death, the few diplomats and foreign correspondents that were permitted inside the Soviet Union were usually restricted to within a few kilometers of Moscow, while their phones were tapped, their residences were restricted to foreigner-only locations, and they were constantly followed by Soviet authorities. Dissenters who approached such foreigners were arrested. For many years after World War II, even the best informed foreigners did not know the number of arrested or executed Soviet citizens, or how poorly the Soviet economy had performed.

Bolsheviks took power in Russia following the Russian Revolution of 1917. During the Russian Civil War that followed, coinciding with the Red Army's entry into Minsk in 1919, Belarus was declared the Socialist Soviet Republic of Byelorussia. After more conflict, the Byelorussian Soviet Socialist Republic was declared in 1920. With the defeat of Ukraine in the Polish-Ukrainian War, after the March 1921 Peace of Riga following the Polish-Soviet War, central and eastern Ukraine were annexed into the Soviet Union as the Ukrainian Soviet Socialist Republic. In 1922, the Russian SFSR, Ukraine SSR, Byelorussian SSR and Transcaucasian SFSR were officially merged as republics creating the Union of Soviet Socialist Republics, or Soviet Union.