The Soviet Union officially ceased to exist as the Supreme Soviet, its highest governmental body, voted to dissolve itself. This marked the end of the Cold War era and led to significant geopolitical changes, including the emergence of 15 independent republics and the reorientation of global power dynamics.

Mikhail Gorbachev resigned as President of the Soviet Union, acknowledging the dissolution of the USSR. His resignation marked the official end of Soviet governance, transferring power to the newly independent republics and concluding the era of Soviet rule.

Leaders of Russia, Ukraine, and Belarus signed the Belavezha Accords, declaring the Soviet Union effectively dissolved and establishing the Commonwealth of Independent States (CIS). This agreement marked the formal end of the Soviet Union, as it acknowledged the independence of its republics.

Hardline members of the Soviet government attempted a coup to overthrow Gorbachev and halt his reform policies. The coup failed after three days due to lack of support and resistance led by Boris Yeltsin. The event further destabilized the Soviet Union and hastened its dissolution.

The Russian Soviet Federative Socialist Republic declared its sovereignty, asserting its laws over Soviet laws. This declaration was a pivotal moment, as Russia was the largest and most influential republic within the USSR, and its move towards independence significantly weakened the Soviet Union's cohesion.

Lithuania became the first Soviet republic to declare independence, challenging Soviet authority and inspiring other republics to seek sovereignty. This declaration was a critical moment in the dissolution process, as it demonstrated the weakening control of the central Soviet government.

The Berlin Wall, a symbol of Cold War division, fell as East Germany opened its borders, allowing free movement between East and West Berlin. This event marked a significant turning point in the decline of Soviet influence in Eastern Europe and accelerated the push for reform within the USSR.

U.S. President Ronald Reagan delivered a speech at the Brandenburg Gate in West Berlin, famously urging Soviet leader Mikhail Gorbachev to 'tear down this wall.' The speech symbolized the growing pressure on the Soviet Union to reform and contributed to the momentum for change in Eastern Europe.

The Chernobyl nuclear disaster occurred in the Ukrainian SSR, causing widespread environmental and health impacts. The Soviet government's delayed response and lack of transparency highlighted systemic issues within the USSR, contributing to public disillusionment and loss of trust in the government.

Mikhail Gorbachev was appointed as the General Secretary of the Communist Party of the Soviet Union, marking the beginning of significant reforms. His policies of glasnost (openness) and perestroika (restructuring) aimed to revitalize the Soviet economy and society but inadvertently accelerated the dissolution process.