Causes of the Cold War
An event that took less than one second to unfold shaped the remainder of the 20th century and the beginning of the 21st.  The destruction of two Japanese cities, Hiroshima and Nagasaki, with the use of atomic bombs, ended WWII.  The unveiling of this super-weapon caused the Allied nations of the world to realign themselves in an effort to either gain access to atomic technology or to secure it and keep it from others.  This arms race for atomic and then nuclear weaponry is considered a long-term cause of the Cold War. 

There were a number of immediate causes at the end of WWII that were also responsible.  Josef Stalin refused to allow free elections in the Soviet-controlled territories and imposed communism instead, creating satellite states.  The United States, Great Britain, and France rejected the practices of Stalin.  Stalin was considered to be as untrustworthy, sinister, and evil as Hitler had been.  British Prime Minister Winston Churchill described the spread of communism and the control of Stalin by saying,
"A shadow has fallen upon the scenes so lately lighted by the Allied victories. . . . From Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the continent." 
Europe was divided into eastern and western blocs.  President Truman settled on a policy of containment which is called the Truman Doctrine.  Containment was the idea that the spread of communism and Soviet control must be stopped, or contained.  Stalin viewed this as a threat, which created a conflict that would last nearly half a century. 

In the aftermath of WWII, Europe was in a state of ruin, with people living in constant hunger and abject poverty.  The United States sought to relieve some of this suffering through economic aid called the Marshall Plan.  This aid package included the rebuilding of Germany, which Stalin saw as a threat.  Therefore, Germany was divided into an eastern and western half.  The city of Berlin itself was also divided.  The western half of Germany and Berlin was rebuilt by the Marshall Plan, while the Soviet-controlled eastern portion was ignored. Stalin tried to keep Western aid out of Berlin, but failed when Allied planes flew around the clock missions for one year, supplying West Berlin. 

The Berlin Airlift is considered the first victory for the west in the Cold War.  The Soviets went so far as to construct a wall in the center of the city in the 1960's.  The Berlin Wall's stated purpose was to keep capitalism out, but was in reality a wall to keep people from escaping the brutal life under Soviet rule.  The policies of both sides created greater tension between the superpowers and by the 1950's military alliances had been formed with each side expecting the other to attack. 

The United States, Canada, and most of the free nations of Western Europe formed NATO, the North Atlantic Treaty Organization.  Conversely, the Soviet Union created the Warsaw Pact, an alliance between the USSR and its satellite nations.  The satellite nations were more of a buffer zone used to protect from invasion than a true alliance system.  The military alliances also engaged in an escalating arms race in which each side tried to outpace the other in nuclear arms production and strength.  In fact, both sides had enough to destroy the planet ten times over in what Churchill called a "balance of terror."  Fortunately, neither side was willing to take the final step to actually firing upon the enemy in anger. 

Major Events of the Cold War Throughout the World
The Soviet Union had problems maintaining control over its satellite states.  Life was virtually unbearable despite the promises of communism, and any group willing to fight the Soviets had the support of the United States.  In 1956, shortly after taking power with the death of Stalin, Nikita Khrushchev, ordered Soviet troops into Hungary to put down a rebellion.  Hungarian freedom fighters had believed the West would help.  It did not, which allowed the Soviet government uncontested control in eastern Europe.  In 1968, the Soviets invaded Czechoslovakia under the leadership of Leonid Brezhnev, who claimed that the Soviet Union had the right to involve itself in the affairs of any communist country. This is known as the Brezhnev Doctrine.

The world teetered on the brink of destruction during the Cuban Missile Crisis of 1961.  Fidel Castro had allied himself with the Soviet Union for economic support and protection from the United States.  The U.S. had been involved in the Bay of Pigs invasion, which had failed.  Khrushchev then began building Soviet missile installations in Cuba.  Upon discovery, the United States confronted the Soviet Union and demanded the missiles be removed.  For nearly two weeks, nuclear war was imminent.  Eventually, diplomacy succeeded and war was averted. 

The Korean War was the first instance of open warfare which pitted communism against capitalism.  The U.S. believed in the domino theory, which stated that nations sharing borders with communist countries were in imminent danger of falling under the sway of that country.  North Korea had become a communist state with the backing of Mao Zedong's China.  South Korea had chosen democracy in the wake of WWII. 

In 1950, North Korea invaded South Korea by crossing the 38th Parallel, the latitude line which divided the Korean peninsula.  The invasion forced the United Nations into involvement with UN forces being comprised largely of American troops.  American involvement brought China into the war which raged back and forth across the 38th Parallel for three years of brutal fighting, often in sub-zero conditions.  In 1953, an armistice, or end to conflict, was signed which re-established the 38th parallel as the border between North and South Korea.  Therefore, three years of war resulted in absolutely nothing. 

The Vietnam Conflict was similar to the Korean War.  Communist Northern Vietnam had invaded democratic Southern Vietnam in the early 1960's.  Northern forces, the Viet Cong, were under the leadership of Ho Chi Minh and were receiving aid from the Soviet Union and China.  As guerrilla tactics were proving effective against American forces, the U.S. escalated the conflict by sending in more troops.  This escalation, and the subsequent invasions of Cambodia and Laos, turned the American public against its government.  Finally, under the leadership of Richard Nixon, American troops left Vietnam, ending the war in the early 1970's. 

The Cold War experienced an easing of tension in the 1970's called détente.  However, this relative peace was shattered with the Soviet invasion of Afghanistan in 1979.  The USSR was forcibly exerting its power in a effort to establish Afghanistan as a communist state.  For ten years, a poorly trained and equipped Soviet army was repeatedly beaten by Afghan guerrilla forces being supplied by the United States.  The Soviet economy was completely disrupted and the Soviet public demanded an end to the war.  Many comparisons can be made with this conflict and the one between the United States and Vietnam. 

The Collapse of Communism
Cracks began to appear in the iron curtain by the mid-1980's.  Movements in many of the satellite nations were calling for change. Most notably was the role played by Lech Walesa of Poland and his Solidarity movement.   Under the leadership of Mikhail Gorbachev, the Soviet Union did make some attempts at reform and an easing of communist hard-line policies.  Perestroika was a complete overhaul in the structure of the Soviet government and economy.  Another reform policy, called Glasnost, was the creation of an open atmosphere in national and global affairs.  Despite the efforts at change, the Soviet Union had already weakened to the point where it was not able to recover. 

A major sign of this was its loss of control of East Germany.  In 1989, the Berlin Wall was literally torn apart by the citizens of both East and West Berlin.  The fall of the wall and the reunification of Germany was one of the most dramatic episodes in 20th century history. 

By the end of the 1980's, Gorbachev was blamed for the decline of the Soviet Union.  In an attempt to regain power, he began reversing some of his reforms, and attempted to return to hard-line communism.  His biggest critic, Boris Yeltsin, called on the nationalistic pride of Russians and demanded Gorbachev's resignation. 

Following Yeltsin's lead, many of the satellite states called for independence.  Gorbachev was close to giving in, which terrified conservative communists still in the government.  These hard-liners attempted a military coup d'état in 1991, but failed after a total lack of support on the part of the military and the public.  Yeltsin saw this as his opportunity and denounced the leaders of the coup in what is known as the Russian Revolution of 1991. 

Yeltsin went on to declare Russia an independent state.  The authority of the Soviet Union was discarded, and communism came to an abrupt end in Eastern Europe.  Yeltsin was elected president of the newly formed Commonwealth of Independent States, which included Russia and many of the former republics of the Soviet Union.