1917: The Russian Revolution overthrows the monarchy and establishes the Soviet government.
1922: The Soviet Union is formed from the union of the Russian Soviet Federative Socialist Republic, the Transcaucasian Soviet Federative Socialist Republic, the Ukrainian Soviet Socialist Republic, and the Byelorussian Soviet Socialist Republic.
1924: Joseph Stalin becomes the leader of the Soviet Union following the death of Vladimir Lenin.
1939-1945: The Soviet Union participates in World War II, fighting against Nazi Germany and its allies. The Soviet Union suffers immense losses, with estimates of up to 27 million Soviet citizens killed.
1945-1989: The Soviet Union becomes a superpower and engages in the Cold War with the United States and its allies. Tensions between the two sides lead to proxy wars and arms races.
1953: Joseph Stalin dies and is succeeded by Nikita Khrushchev.
1961: The Soviet Union launches the first human into space, Yuri Gagarin, aboard the Vostok 1 spacecraft.
1962: The Cuban Missile Crisis brings the world close to nuclear war as the Soviet Union places missiles in Cuba.
1985: Mikhail Gorbachev becomes the leader of the Soviet Union and implements reforms, including glasnost (openness) and perestroika (restructuring).
1989: The fall of the Berlin Wall marks the beginning of the end of the Cold War.
1991: Following a failed coup attempt, the Soviet Union dissolves, with the individual republics declaring independence. Boris Yeltsin becomes the first president of the Russian Federation, the largest and most influential of the former Soviet republics.