The Soviet Union (SU or USSR) was a state in Eastern Europe, Central and Northern Asia that existed from 1922 to 1991. It emerged from the so-called Soviet Russia, the successor state of the Russian Empire. The Russian Soviet Republic formed the core of the union and at the same time its largest part, with further constituent republics added. Their number varied over time and was related to the occupation of other countries (Estonia, Latvia, Lithuania), Soviet republics that existed only for a short time (Karelo-Finlandia) or the division or merger of Soviet republics. In addition, there were numerous autonomous republics or other territorial units with an autonomy status that was essentially limited to linguistic autonomy for minorities.
Before its formal dissolution, the USSR consisted of 15 Soviet republics with a population of approximately 290 million people. At around 22.4 million km², it was the largest territorial state in the world at the time. The Soviet Union was a socialist soviet republic with a one-party system and an absence of separation of powers.
The People's Republic of Poland was a socialist state in the Soviet sphere of influence that existed from 1944 to 1989 (until 1952 as the Republic of Poland). Its borders correspond to those of present-day Poland. The legitimacy of the form of government was based on the 1946 referendum and the 1947 election, the results of which were, however, falsified. In 1948, the parties of the so-called Democratic Bloc were forcibly merged into the Socialist Unity Party of the one-party state. The communist Polish United Workers' Party (Polska Zjednoczona Partia Robotnicza, PZPR) ruled until the end of the People's Republic.
Czechoslovakia was a state existing between 1918 and 1992 with changing borders, names, and political systems. Its territories are now part of the modern-day states of Czechia, Slovakia, and Ukraine (Carpathian Ukraine, occupied by Hungary in 1939 and transferred to the Soviet Union in 1945). After 1945, Czechoslovakia came under increasing political influence from the Soviet Union. After the communist party seized power in 1948, the country finally became part of the so-called Eastern Bloc, a satellite state of the Soviet Union, and a member of the Warsaw Pact from 1955. Between 1960 and 1990, the communist country was officially known as the Czechoslovak Socialist Republic (abbreviated to ČSSR). The democratic political change was initiated in 1989 with the Velvet Revolution and culminated in 1992 with the founding of the independent Czech and Slovak Republics.
The People's Republic of Hungary was a socialist state in East Central Europe that existed from 1949 to 1989. The occupation of Hungary by the German Wehrmacht began in 1944, followed by the Red Army, which occupied the entire country in 1945. After the end of the war, attempts to establish a democracy failed and the political system was successively transformed into a one-party system under communist leadership.
The People's Republic of Hungary was a member of the Warsaw Pact and was under the strong political influence of the Soviet Union, which violently suppressed the Hungarian uprising in 1956 with the help of the Warsaw Pact states (except Romania). To appease the population after the wave of reprisals against the participants of the uprising, economic and political reforms were introduced in the 1960s that went beyond the usual restrictions in the Eastern Bloc. In connection with the economic crisis of the late 1980s, further economic reforms and extensive political liberalization as well as opening to the West were gradually introduced, which also heralded the end of the socialist People's Republic. In 1989, the present-day Republic of Hungary was finally proclaimed.
