During the Soviet era, the union republics—also known as the Soviet Socialist Republics (SSRs)—were the constituent parts of the Soviet Union. Since the 1950s, there have been 15 union republics (the Russian Soviet Federative Socialist Republic, Ukraine, Belarus, Moldova, Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Uzbekistan, Turkmenistan, Tajikistan, Estonia, Latvia, and Lithuania), each with a titular nation. Prior to World War II, the last three—collectively known as the Baltic States—had been independent countries, and their annexation into the Union of Soviet Socialist Republics (USSR) as union republics was never recognized by many Western governments. Moldova was created on 2 August 1940 through a merger of Ukrainian territory and lands annexed from neighboring Romania. From 1940 to 1956, Kareliya was known as the Karelo-Finnish SSR, making it the 16th union republic. Nominally a federation, the USSR permitted the right of secession to each republic. During the summer of 1991, the Baltic States seceded from the union. In early December 1991, Russia, Belarus, and Ukraine de facto exercised this right by signing the Belavezha Accords. On 25 December 1991, the Alma-Ata Protocol completed the dissolution of the Soviet Union, with the remaining republics gaining their independence. During the late Gorbachev era, the parliaments of a number of Russia’s Autonomous Soviet Socialist Republics (ASSRs), including Chechnya, unsuccessfully attempted to elevate their status to that of a union republic.
Historical Dictionary of the Russian Federation. Robert A. Saunders and Vlad Strukov. 2010.