the Cold War Yalta Conference Communist takeover in Czechoslovakia NATO ratified Korean War CIA helps overthrow unfriendly regimes in Iran and Guatemala Sputnik launched into orbit Soviet Union reveals that U.S. spy plane was shot down over Soviet territory Nuclear Test Ban Treaty ratified Soviet troops crush Czechoslovakian revolt Apollo 11 lands on the moon Mikhail Gorbachev ascends to power in Soviet Union Reagan and Gorbachev agree to remove all medium and short-range nuclear missiles by signing treaty Soviet troops withdraw from Afghanistan Communist governments fall in Czechoslovakia, Bulgaria, and Rumania; Soviet empire ends Boris Yeltsin elected to presidency of Russia End of Soviet Union Cold War Ends