Study Guide

Causes of the Cold War Timeline

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Aug 10, 1945

Korea Divided at 38th Parallel

At the end of World War II, Korea—occupied during the war by Japanese forces—is divided at the 38th Parallel, and two new states are established. North Korea is run by communist Kim Il-Sung, while South Korea is run by anticommunist autocrat Syngman Rhee.

Feb 4, 1945 - Feb 11, 1945


The "Big Three" allied leaders—United States President Franklin Roosevelt, Soviet leader Joseph Stalin, and British Prime Minister Winston Churchill—meet at the Yalta Conference to make arrangements for the postwar world order. Their contradictory agreements include a declaration to respect democracy throughout Europe, but also the recognition of a de facto Soviet sphere of influence in Eastern Europe. At Yalta, the Allies also finalize plans to divide Germany into separate zones of occupation.

Apr 12, 1945

Roosevelt Dies

President Franklin D. Roosevelt suddenly suffers a cerebral hemorrhage and dies, leaving his vice president, Harry Truman, to assume the presidency. Truman has only been vice president for 82 days, and has had little communication with Roosevelt about the administration's policies. After taking his oath of office, Truman tells reporters, "Boys, if you ever pray, pray for me now" (source).

Jun 26, 1945

United Nations Founded in San Francisco

The United Nations Charter is adopted in San Francisco, California, by representatives of 51 countries. This marks the founding of the UN.

Jul 16, 1945

First Atomic Bomb

American scientists successfully test the first atomic bomb in New Mexico.

Jul 17, 1945 - Aug 2, 1945


The "Big Three" leaders of the United States, Soviet Union, and Great Britain meet at the Potsdam Conference. President Harry Truman, Soviet leader Joseph Stalin, and British Prime Minister Winston Churchill continue the work begun at Yalta to determine the future of postwar Europe. Churchill is replaced midway through the negotiations by new Prime Minister Clement Attlee after Churchill's party loses elections in Britain. The conference establishes a military administration for Germany and agrees to put Nazi leaders on trial for war crimes.

Aug 6, 1945


The American bomber Enola Gay drops an atomic bomb nicknamed "Little Boy" on the Japanese city of Hiroshima. The instant devastation unleashed on Hiroshima shocks the world and ushers in the nuclear age.

Aug 8, 1945


The American plane Bockscar drops an atomic bomb nicknamed "Fat Man" on the Japanese city of Nagasaki.

Sep 2, 1945

Ho Chi Minh Declares Independence

Vietnamese nationalist Ho Chi Minh declares Vietnam's independence from France. Ho's Vietnamese Declaration of Independence quotes the American Declaration of 1776 to assert that "All men are created equal."

Jul 1, 1946 - Jul 25, 1946

Bikini Atoll Tests

Idyllic Bikini Atoll, in the South Pacific, becomes the site of a series of giant nuclear weapons tests. Codenamed Operation Crossroads, these tests are part of a study of radiological effects and are also shown to the Soviets as a demonstration of the weapons' power.

Aug 1, 1946 - Aug 31, 1946

Mao's Paper Tiger

In an interview with American correspondent Anna Louise Strong, Chinese communist leader Mao Zedong dismisses the atom bomb as nothing more than a "paper tiger."

Feb 22, 1946

George Kennan and Containment

Diplomat George Kennan writes his "Long Telegram" from the U.S. Embassy in Moscow, advocating a policy of containment: "It is clear that the main element of any United States policy towards the Soviet Union must be that of a long-term, patient but firm and vigilant containment of Russian expansive tendencies [...] It is clear that the United States cannot expect in the foreseeable future to enjoy political intimacy with the Soviet regime. It must continue to regard the Soviet Union as a rival, not a partner, in the political arena."

Mar 5, 1946

Iron Curtain

British Prime Minister Winston Churchill gives his famous "Iron Curtain" speech at a college graduation in Fulton, Missouri: "From Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the Continent. Behind that line lie all the capitals of the ancient states of Central and Eastern Europe. Warsaw, Berlin, Prague, Vienna, Budapest, Belgrade, Bucharest and Sofia; all these famous cities and the populations around them lie in what I must call the Soviet sphere, and all are subject, in one form or another, not only to Soviet influence but to a very high and in some cases increasing measure of control from Moscow."

Dec 19, 2019

GATT Agreed

The General Agreement on Tariffs and Trade (GATT) is developed as 23 Western nations, including the U.S., agree on freer trade. The GATT creates new markets for American goods and investment abroad.

Dec 2, 1946

German Zones Merge

The United States and Great Britain agree to merge their respective German zones of occupation.

Mar 12, 1947

Truman Doctrine

In a speech later remembered as the Truman Doctrine, President Harry S. Truman pledges American assistance to any nation in the world threatened by communism, officially establishing the worldwide containment of communism as a vital American national security interest.

Jun 5, 1947

Marshall Plan

In a speech made at Harvard University, Secretary of State George Marshall proposes the Marshall Plan, a $13 billion foreign aid package designed to help Europe recover from the devastation of World War II.

Jan 1, 1946 - Dec 31, 1948

MacArthur Commands

General Douglas MacArthur serves as "supreme commander" of Japan as the country adopts a new democratic constitution. MacArthur halts a plan to dissolve Japan's largest industrial corporations and instead uses them to rebuild Japan as an anticommunist bastion.

Jun 28, 1948

Tito Rebuffs Moscow

Yugoslavia's communist leader, Marshal Josip Tito, refuses to bend to Stalin's will and breaks with Moscow after years of an uneasy alliance.

Feb 1, 1948

Czech Communists Win

Czechoslovakian communists win control of the national government via a coup against liberal leaders Eduard Benes and Jan Masaryk. Masaryk is killed after falling out a window under suspicious circumstances.

Apr 18, 1948

U.S. Italians Against Communists

Concerned about the possibility of a communist victory in the upcoming Italian elections, the U.S. government undertakes a campaign to get Italian Americans to write letters urging their relatives in Italy to vote against the communists. Italy's elections result in a landslide victory for the anticommunist Christian Democrats.

Jun 24, 1948

Berlin Blockade

After the United States, Britain, and France introduce the Deutsche Mark to serve as a single currency for their three zones of occupation in Western Germany, the Soviets impose the Berlin blockade, cutting off rail and road access to the capital city, which is located in the middle of the Soviet zone of Eastern Germany.

Jun 24, 1948 - May 11, 1949

The Berlin Airlift

Under General Lucius Clay, the United States begins Operation Vittles—the 11-month Berlin Airlift—which brings necessary supplies into the city by plane. The airlift represents an immense feat of coordination, with planes landing and being unloaded around the clock for nearly a year.

Nov 2, 1948

Truman Surprise Reelection

American voters reelect Democrat Harry Truman to serve another term as president. The unpopular Truman's narrow victory over Republican Thomas Dewey comes as a major upset.

Jan 8, 1949

Economic Cooperation

COMECON, the Council for Mutual and Economic Cooperation, is formed as a Soviet answer to the Marshall Plan. The Soviets recognize the popularity of the Marshall Plan and seek to match it to prevent their own satellite nations from defecting to the West.

Apr 4, 1949

NATO Formed

Ten Western European nations join the United States and Canada to form the North Atlantic Treaty Organization (NATO), an anti-Soviet military alliance that extends the deterrent threat of America's nuclear weapons to cover Western Europe.

Mar 1, 1950

Stalin Concedes to Korean Invasion

North Korean leader Kim Il-Sung goes to Moscow to ask Soviet leader Joseph Stalin's permission to invade South Korea and begin the Korean War. Stalin gives the green light because he believes the United States has little interest in Korea.

May 24, 1949

West Germany Forms with Basic Law

The former zones of British, French, and American occupation officially become the state of West Germany after the adoption of a new German constitution known as the Basic Law. Elections are held and Konrad Adenauer becomes chancellor, a position he will hold until 1963.

Aug 29, 1949

Soviet Atomic Bomb

The Soviet Union detonates its first atomic bomb, causing shock and fear in the United States.

Oct 1, 1949

Communist Win in China

Chinese communist leader Mao Zedong declares the People's Republic of China as the communists win their civil war against Chiang Kai-Shek's Nationalists, who flee to Taiwan.

Oct 7, 1949

East Germany Founded

In response to the founding of West Germany, the Soviets declare the establishment of East Germany under the leadership of communist Walter Ulbricht.

Dec 21, 1949

Chinese and Soviet Alliance

Soviet leader Joseph Stalin celebrates his 70th Birthday, and Chinese leader Mao Zedong visits Moscow to negotiate an alliance with the Soviet Union.

Dec 1, 1950 - Dec 31, 1950

NATO Forms Military Command

NATO (North Atlantic Treaty Organization) forms a joint military command, choosing American General Dwight Eisenhower as Supreme Commander. NATO's ground forces grow from 30 divisions in 1950 to nearly 60 in 1953.

Apr 18, 1950

Nuclear Fear

American official Paul Nitze issues the National Security Council report NSC-68. The report predicts a Soviet nuclear attack and calls for greater defense spending.

Jan 12, 1950

Defensive Perimeter to Protect Asia

In a speech, Secretary of State Dean Acheson pledges that the United States will fight to defend all territory within its "defensive perimeter," which he defines to include Japan, and the Philippines—but not Korea. Soviet leader Joseph Stalin misinterprets this speech as to indicate that he can green-light North Korean leader Kim Il-Sung's "liberation" of South Korea with little risk of intervention by the United States.

Feb 1, 1950 - Feb 28, 1950

Vietnam and Soviets Ally

Vietnamese nationalist leader Ho Chi Minh visits Soviet leader Joseph Stalin to discuss whether an alliance will be beneficial.

Feb 14, 1950

Sino-Soviet Treaty

Soviet leader Joseph Stalin and Chinese leader Mao Zedong sign the Sino-Soviet Treaty of Friendship, Alliance, and Mutual Assistance, an agreement committing the two nations to 30 years of mutual defense.

Jun 25, 1950

North Attacks South Korea

The Korean War begins as North Korean troops attack across the 38th parallel in an effort to "liberate" South Korea.

Jun 27, 1950

U.S. Aids South Korea

President Harry Truman orders American forces to assist South Korea, which is being overrun by communist North Korean troops.

Dec 19, 2019

Origins of Totalitarianism

Hannah Arendt's Origins of Totalitarianism proposes that both Nazism and communism are forms of the same political tendency, totalitarianism, which she defines as authoritarian politics that mobilizes mass support and uses terror to crush resistance.

Jul 10, 1951

Negotiations Begin in Korea

Peace negotiations begin in Korea, but will drag on for two more years. Combat continues.

Apr 11, 1951

MacArthur Fired

After General Douglas MacArthur publicizes his disagreements with President Truman's "limited war" policy, which prevents MacArthur from using nuclear weapons, Truman accuses MacArthur of insubordination and removes him from command of American forces in Korea. The removal of MacArthur—an iconic and popular World War II leader—provokes a huge public outcry in the United States, where MacArthur is greeted as a hero upon his return.

Apr 28, 1952

U.S. Ends Japanese Occupation

Nearly seven years after V-J Day, the United States ends its military occupation of Japan.

Nov 4, 1952

Eisenhower Elected

Republican Dwight D. Eisenhower, the famous World War II general, defeats Democrat Adlai Stevenson in the American presidential election.

May 26, 1952

German Border

The Soviets close the border between East and West Germany, but not between East and West Berlin. The capital city becomes a gateway for people wishing to cross between the two Germanys, mainly fleeing from the communist East to the more prosperous West.

Nov 1, 1952

Hydrogen Bomb

The United States explodes its first hydrogen bomb—a weapon hundreds of times more powerful than the atomic bombs dropped on Japan in 1945—at Enewetak in the South Pacific.

Jun 17, 1953

East Germans Riot

In East Berlin, a general strike devolves into rioting as demonstrators begin to demand free elections from the communist government. These demonstrations represent the first signs of violent discontent in the Soviet bloc. Moscow responds by sending in Red Army troops to crush the demonstrators.

Aug 19, 1953

CIA Backs Iranian Coup

In Iran, the CIA sends agents to overthrow Mohammed Mossadegh, the democratically elected leader who has nationalized the Anglo-Iranian Oil Company, Britain's largest overseas asset. After deposing Mossadegh, the CIA restores the Western-friendly but unpopular Shah Reza Pahlavi as ruler of Iran.

Aug 12, 1953

Soviets Develop Hydrogen Bomb

The Soviets explode their first hydrogen bomb, a mere nine months after the United States accomplished the same feat. The Soviets' determination to keep up with American technological developments signals their commitment to the arms race.

Mar 5, 1953

Stalin Dies

Soviet leader Joseph Stalin dies, ending his 30-year stranglehold on power within the Soviet Union.

Jul 27, 1953

Korean Armistice Signed

An armistice is signed, ending the Korean War and creating a demilitarized zone (DMZ) at the border between North and South.

Sep 7, 1953

Khrushchev Leads Soviets

Nikita Khrushchev becomes Soviet Communist Party leader after triumphing in the intra-party power struggles that follow Joseph Stalin's death.

Apr 7, 1954

Domino Theory

President Dwight Eisenhower publicly articulates the "Domino Theory" in reference to the threat of communist gains in Indochina. The theory holds that the fall of one nation (like Indochina) to communism might lead, like a chain of dominoes, to the fall of neighboring nations as well.

Jan 12, 1954

Massive Retaliation

Secretary of State John Foster Dulles makes his "Massive Retaliation" speech, marking the official implementation of brinksmanship as deterrent strategy. According to the policy of massive retaliation, any Soviet-led attack on an ally of the United States will be met by a direct American nuclear assault against the Soviet Union. The strategy will allow for a reduction in the American military budget because its emphasis on nuclear weapons decreases the importance of maintaining a large conventional army, which can now be downsized.

May 7, 1954

Dien Bien Phu

Vietnamese nationalist leader Ho Chi Minh and his troops defeat French forces in a siege at the French base in Dien Bien Phu.

Jun 27, 1954

CIA Sponsors Coup in Guatemala

After leftist Guatemalan President Jacobo Arbenz nationalizes American-owned banana plantations, the CIA sponsors a coup to topple the democratically-elected Arbenz government.

Apr 27, 1954

Geneva Accords Signed

The Geneva Accords split the colony of French Indochina into three new nations—Laos, Cambodia, and Vietnam—and further divide Vietnam at the 17th parallel, to be reunited following elections in 1956. South Vietnamese leader Ngo Dinh Diem refuses to hold the mandated elections, knowing he will lose to the much more popular North Vietnamese communist leader Ho Chi Minh.

Aug 11, 1954 - May 1, 1955

Quemoy Crisis

Communist Chinese forces begin shelling Quemoy, a small island held by the Nationalist government of Taiwan. Since Quemoy lies in the strait between the mainland and Taiwan, Nationalist officials fear the shelling represents a communist threat to invade Taiwan proper. The United States considers using nuclear weapons to protect its ally in accordance with the policy of massive retaliation, but President Dwight Eisenhower decides against such a drastic step. The Quemoy crisis highlights the fundamental flaw in massive retaliation—no one wants to have to start World War III over a tiny island in the Strait of Taiwan. In this case, however, the mere threat of nuclear war is enough to win success; China eventually backs down when the Soviets fail to offer nuclear support in case of an attack.

May 14, 1955

Warsaw Pact

The Soviet Union forms the Warsaw Pact, a communist military alliance intended to counter the threat posed by the West's North Atlantic Treaty Organization (NATO).

Jul 21, 1955

Open Skies

President Eisenhower and Soviet Premier Nikolai Bulganin meet in Geneva for the first postwar Soviet-American summit meeting. Eisenhower makes his "Open Skies" proposal to the Soviets, offering to allow each superpower to conduct surveillance flights over the other in order to put to rest both sides' fears of surprise attacks. Bulganin rejects the idea.

May 5, 1955

West Germany Sovereign

West Germany is declared "fully sovereign," no longer under any form of Allied occupation.

May 9, 1955

West Germany in NATO

West Germany is admitted to the North Atlantic Treaty Organization (NATO), the Western military alliance.

Jan 1, 1955

China Pursues Bomb

Chinese leader Mao Zedong decides China should build its own nuclear bomb.

Oct 1, 1956 - Jul 31, 1957

100 Flowers Movement

China's 100 Flowers movement begins after Chairman Mao decides to allow "healthy criticism" and open debate on economic growth and the rule of Communist Party. "Healthy criticism" soon swells into a clamor of dissent, however, prompting Mao to shut 100 Flowers down after less than a year.

Feb 25, 1956

Secret Speech Denounces Stalin

Soviet Premier Nikita Khrushchev's "secret speech" to the 20th Party Congress in Moscow reveals and denounces the past crimes of deceased former Soviet leader Joseph Stalin. Khrushchev also calls for peaceful coexistence between capitalists and communists. In his subsequent de-Stalinization campaign, Khrushchev will release political prisoners, improve Soviet citizens' access to consumer goods, and allow for growing freedom in Soviet literature.

Jul 4, 1956

U2 Spy Plane Developed

Americans fly the first U2 spy plane over Moscow. The U2 is designed to fly at such a high altitude that it remains out of range of Soviet weapons and undetectable to Soviet radar.

Jan 25, 1957

Eisenhower Doctrine

In a speech that will come to be called the Eisenhower Doctrine, President Eisenhower pledges to provide military and economic aid to countries fighting communism in the Middle East.

Mar 25, 1957

Treaty of Rome

The Treaty of Rome—signed by France, West Germany, Italy, the Netherlands, Belgium, and Luxembourg—establishes the European Community (or Common Market), which expands upon the framework established by the 1951 European Coal and Steel Community to establish a Western European free trade zone. The treaty reflects many Europeans' aspirations to establish an independent body to look out for European interests rather than the American objectives that are perceived to drive NATO policy. The European Community lays the foundation for what will eventually become the European Union.

Oct 4, 1957

Sputnik Launched

The Soviets launch Sputnik, the first man-made object to orbit the earth. The Soviets' technological success in building the world's first satellite strikes fear in the hearts of Americans and launches the space race.

Nov 6, 1957

Mao Travels

Chinese leader Mao Zedong travels to Moscow for the 40th Anniversary of the Soviet Revolution and declares that "East Wind is rising over West Wind," reflecting his belief that China will overtake the Soviet Union as the world's leading communist power.

Oct 22, 1956

Hungarian Revolution

The Hungarian Revolution begins when student protesters demand changes to the communist government's national policies. The government falls and protesters organize to resist an invasion by Soviet troops.

Oct 24, 1956

Imre Nagy Runs Hungary

Imre Nagy becomes Prime Minister of Hungary during the revolution, quickly arranging a cease-fire but then cautiously backing the revolutionaries' calls for change.

Oct 31, 1956

Hungary Leaves Warsaw Pact

Hungarian leader Imre Nagy announces his nation's withdrawal from the Warsaw Pact—a repudiation of his country's alliance with the Soviet Union—as the next step in the Hungarian Revolution.

Nov 4, 1956

Soviets Crush Hungary

The Hungarian Revolution is crushed by a Soviet Red Army invasion. Hungarian leader Imre Nagy waits in vain for Western help, but the Soviets install a new, servile government under staunch communist Janos Kadar. Repression of dissidents grows intense and many Hungarian refugees flee to the West.

Jan 1, 1958 - Jan 31, 1961

Great Leap Forward

Under Mao Zedong's leadership, China begins the Great Leap Forward, a plan to industrialize the nation. The state takes over land, changes agricultural practices, and places people on huge communes to produce steel. The Great Leap Forward fails miserably to produce progress for China, resulting instead in a Great Famine as agriculture is sacrificed for industry. Millions die.

Jun 16, 1958

Imry Nagy Executed

Former Hungarian Revolution leader Imre Nagy is executed by the Soviets after a secret trial.

May 12, 1958

North American Defense

The United States and Canada join together to form the North American Aerospace Defense Command (NORAD) to monitor the skies for Soviet nuclear attack.

Jan 31, 1958

First Satellite

The United States launches its first satellite, Explorer.

Aug 23, 1958 - Oct 6, 1958

China Attacks Taiwan

For the second time in four years, China shells the islands of Quemoy and Matsu in the Taiwan Strait, seeking to intimidate the nearby Republic of China (a.k.a. Taiwan), which owns the islands. The United States once again provides support for Taiwan's defense.

Jul 29, 1958

NASA Created

The United States creates NASA, the National Aeronautics and Space Administration, to lead the space race with the Soviet Union.

Jul 24, 1959

Kitchen Debate

Vice President Richard Nixon and Soviet leader Nikita Khrushchev engage in the so-called "kitchen debate" in Moscow. Nixon touts the high standard of living in the United States and the freedom of choice among consumer products as proof of the superiority of capitalism.

May 1, 1960

U2 Shot Down Over Soviet Union

American pilot Gary Powers' U2 spy plane is shot down over the Soviet Union. President Eisenhower denies responsibility for the international incident and refuses to apologize, precipitating the collapse of a planned Paris summit between the United States and Soviet Union.

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