Final answer:
The claim that Gorbachev allowed Eastern European reforms without Soviet intervention, in contrast to previous Soviet military suppressions, is true. His policies of 'glasnost' and 'perestroika' led to democratic transitions and ultimately the Soviet Union's dissolution in 1991.
Step-by-step explanation:
The statement that Mikhail Gorbachev said he wouldn't intervene if Eastern European governments introduced reforms, which allowed democratic revolutions to sweep through Eastern Europe in 1989, is true. This marked a significant shift from earlier years when the Soviet Union had intervened forcefully to maintain control over Eastern Bloc countries, as evidenced in Hungary in 1956 and in Czechoslovakia in 1968 where the Soviets used military might to suppress reform movements. Gorbachev's policies of glasnost (openness) and perestroika (restructuring) facilitated political changes, leading to a series of non-violent transitions from communist to democratic governments in many Eastern European countries. By the end of 1991, the legacy of these transformations contributed to the dissolution of the Soviet Union itself and the end of the Cold War era.