The Republics of the Soviet Union or the Union Republics (Russian: союзные республики, soyuznye respubliki) of the Soviet Unoin were ethnically-based administrative units that were subordinated directly to the Government of the Soviet Union. The Soviet Union was historically a highly centralized state; the decentralization and democratization reforms during the era of Perestroika and Glasnost conducted by Mikhail Gorbachev led to the Dissolution of the USSR.