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 Berlin and West Berlin became a loophole through which defection could occur. This was closed with the erection of the Berlin Wall in 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.
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.
During the final stages of World War II, the Soviet Union began the creation of the Eastern Bloc by directly annexing several countries as Soviet Socialist Republics that were originally effectively ceded to it by Nazi Germany in the Molotov-Ribbentrop Pact.
These included Eastern Poland (incorporated into three different SSRs), Latvia (became Latvia SSR), Estonia (became Estonian SSR), Lithuania (became Lithuania SSR), part of eastern Finland (became Karelo-Finnish SSR, and later merged into the Russian SFSR) and northern Romania (became the Moldavian SSR). By 1945, these additional annexed countries totaled approximately 465,000 additional square kilometers (180,000 square miles), or slightly more than the area of West Germany, East Germany and Austria combined.