Why the Cold War Began: Key Events and Factors That Triggered It

The Cold War began after World War II ended in 1945, from distrust and rivalry between the US and the Soviet Union over ideology and control of Europe.

Origins

The Cold War (about 1947 to 1991) was a rivalry between the US and the Soviet Union, with no direct large-scale fighting between them.

Causes

• Ideology: capitalism and democracy versus communism.
• Disputes over postwar Europe (Poland, Germany) after Yalta and Potsdam (1945).
• Soviet control of Eastern Europe.
• The Truman Doctrine (1947) and Marshall Plan (1948).
• Nuclear weapons: the US used atomic bombs in 1945, and the USSR tested its own in 1949.

Key events

Berlin Blockade (1948), Korean War, Cuban Missile Crisis (1962), Vietnam War.

End

The Berlin Wall fell in 1989. The USSR dissolved in December 1991.

The wartime alliance breaks down

The United States and the Soviet Union fought together against Germany from 1941, but their systems and goals clashed. At the Yalta Conference in February 1945, Roosevelt, Churchill and Stalin agreed to free elections in Eastern Europe, but the Soviets installed communist governments in Poland, Romania, Bulgaria, Hungary and later Czechoslovakia. By 1946 Churchill described an “iron curtain” across Europe in his speech in Fulton, Missouri.

Early flashpoints

• Iran 1946: the Soviet Union delayed withdrawing troops from northern Iran until pressure from the UN and the US.
• Greece and Turkey 1947: the Truman Doctrine pledged US support for countries resisting communism, with $400 million in aid.
• The Marshall Plan: from 1948 the US gave about $13 billion in aid to rebuild Western Europe. Moscow refused it for Eastern Europe.

Berlin and NATO

Germany was split into four occupation zones. In 1948 the Soviets blocked road and rail access to West Berlin, and the Allies responded with the Berlin Airlift, flying more than 2 million tons of supplies in 11 months until May 1949. NATO was formed in April 1949 with 12 members. The Soviets answered with the Warsaw Pact in 1955.

Deeper causes

Ideology clashed: capitalism and democracy against communism and one party rule. Security fears mattered too, as the Soviets had lost about 27 million people in the war and wanted a buffer in Eastern Europe, while the US wanted open markets and feared communist expansion. The US atomic bomb, used in 1945, and the Soviet test in 1949 turned rivalry into an arms race.

Key events that followed

• 1949: the Chinese communist victory and the Soviet atomic bomb.
• 1950 to 1953: the Korean War.
• 1957: Sputnik begins the space race.
• 1961: the Berlin Wall.
• 1962: the Cuban Missile Crisis brought the world close to nuclear war.
• 1965 to 1975: the Vietnam War.

Why it never became direct war

Both sides held large nuclear arsenals, which made direct war too costly, an idea known as mutually assured destruction. The conflict played out through proxy wars, spying, propaganda, and economic competition. At its peak in 1986 the world had about 70,000 nuclear warheads.

End

Reforms under Mikhail Gorbachev, the fall of the Berlin Wall on November 9, 1989, and the dissolution of the Soviet Union on December 26, 1991 ended the Cold War.

Nuclear arms and the early arms race

The United States used atomic bombs on Hiroshima and Nagasaki in August 1945. The Soviet Union tested its first atomic bomb on August 29, 1949, ending the US monopoly, and both sides tested hydrogen bombs in 1952 and 1953. By 1986 the combined US and Soviet stockpile peaked at about 70,000 warheads, according to the Federation of American Scientists. The Cuban Missile Crisis in October 1962 lasted 13 days and is widely seen as the closest the superpowers came to nuclear war. The Cold War lasted until the Soviet Union dissolved on December 26, 1991.

Based on data from the Federation of American Scientists and the US Department of State Office of the Historian