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The Cold War (1945–1963)

History SparkNotes

The Start of the Cold War: 1947–1952

The Postwar World: 1945–1949

The Korean War: 1950–1953

1938 House Un-American Activities Committee created
1947 Doctrine of containment emerges Truman articulates Truman Doctrine Congress passes National Security Act
1948 Alger Hiss accused of being a Soviet operative Truman is reelected
1949 NATO is formed China falls to Communist forces
1950 Congress passes McCarran Internal Security Bill
1951 Julius and Ethel Rosenberg convicted of espionage
1952 United States develops first hydrogen bomb
Key People
Harry S Truman -  33rd U.S. president; announced Truman Doctrine in 1947, which shaped U.S. foreign policy for four decades
Thomas E. Dewey -  New York governor who ran unsuccessfully on the Republican Party ticket against Truman in 1948
George F. Kennan -  State Department analyst who developed containment doctrine in 1947, arguing that Communism and the USSR could not be allowed to spread; this doctrine became the basis of U.S. foreign policy strategy during the Cold War
Richard M. Nixon -  Republican congressman and prominent member of HUAC in the late 1940s; successfully prosecuted Alger Hiss for being a Communist
Alger Hiss -  Former federal employee prosecuted by HUAC in 19481950 for being a Communist and Soviet spy
Julius and Ethel Rosenberg -  Married couple convicted of espionage in 1951 after being wrongfully convicted of selling nuclear secrets to the USSR; executed in 1953
Chiang Kai-shek -  Leader of China’s Nationalist government when Communist forces drove it out of mainland China in 1949
Mao Zedong -  Leader of Communist revolutionaries who brought down China’s Nationalist government in 1949; became ruler of People’s Republic of China as leader of Chinese Communist Party


In 1947, State Department analyst George F. Kennan penned a highly influential essay on the Soviet Union that transformed fear of the USSR into a cohesive foreign policy. Arguing that insecure Russians had always had the desire to expand and acquire territory, Kennan wrote that the Soviet Union would take every opportunity to spread Communism into every possible “nook and cranny” around the globe, either by conquering neighboring countries or by subtly supporting Communist revolutionaries in politically unstable countries. Kennan also wrote, however, that the United States could prevent the global domination of Communism with a strategy of “containment. He suggested maintaining the status quo by thwarting Communist aggression abroad.

Kennan’s containment doctrine rapidly became the root of the dominant U.S. strategy for fighting Communism throughout the Cold War. Different presidents interpreted the doctrine differently and/or employed different tactics to accomplish their goals, but the overall strategy for keeping Communism in check remained the same until the Cold War ended in the early 1990s.

The Truman Doctrine

Truman quickly latched onto the doctrine of containment and modified it with his own Truman Doctrine. In a special address to Congress in March 1947, Truman announced that the United States would support foreign governments resisting “armed minorities” or “outside pressures”—that is, Communist revolutionaries or the Soviet Union. He then convinced Congress to appropriate $400 million to prevent the fall of Greece and Turkey to Communist insurgents.

Critics, both at the time and looking back in retrospect, have charged that Truman’s adoption of the containment doctrine, coupled with his own Truman Doctrine, accelerated the Cold War by polarizing the United States and the USSR unnecessarily. Many have claimed that the United States might have avoided fifty years of competition and mutual distrust had Truman sought a diplomatic solution instead.

Defendants of Truman’s policy, however, have claimed that the Soviet Union had already begun the Cold War by thwarting Allied attempts to reunite and stabilize Germany. Truman, they have argued, merely met the existing Soviet challenge. Other supporters believed that Truman used polarizing language in order to prevent U.S. isolationists from abandoning the cause in Europe. Whatever his motivations, Truman’s adoption of the containment doctrine and his characterization of the Communist threat shaped American foreign policy for the subsequent four decades.

The National Security Act

The possibility of a war with the Soviet Union prompted Congress, Truman, and the military leadership to drastically reorganize the intelligence-gathering services and armed forces. In 1947, Congress passed the landmark National Security Act, which placed the military under the new cabinet-level secretary of defense. Civilians would be chosen to serve in the post of secretary of defense and as the secretaries of the individual military branches, while the highest-ranking officers in the armed forces would form the new Joint Chiefs of Staff to coordinate military efforts. The National Security Act also created the civilian position of national security advisor to advise the president and direct the new National Security Council. The new Central Intelligence Agency became the primary espionage and intelligence-gathering service.

The Election of 1948

Even though he had initially complained about his new responsibilities as president after Roosevelt’s death in 1945, Truman decided to run for reelection as the prospect of another world war loomed. Party leaders nominated him only halfheartedly after World War II hero Dwight D. Eisenhower refused to run on the Democratic ticket. Conservative southern Democrats in particular disliked Truman’s New Deal–esque commitment to labor, civil rights, reform, and social welfare spending. When Truman received the formal party nomination, southern Democrats split from the party and nominated their own candidate, Governor Strom Thurmond of South Carolina. Progressive Democrats also nominated former vice president Henry Wallace on a pro-peace platform.

The Republicans, meanwhile, nominated New York governor Thomas E. Dewey. Most Democrats and even Truman himself believed victory to be impossible. On election night, the Chicago Tribune  printed an early version of the election returns, proclaiming a Dewey win with the infamous headline “Dewey Defeats Truman.” As it turned out, however, Truman received more than two million more popular votes than his nearest challenger, Dewey, and 303 electoral votes. He owed his victory in part to his adoption of the policy of containment but mostly to his commitment to expand Social Security and provide increased social welfare spending as part of his proposed Fair Deal program. Continued Republican and southern Democrat opposition in Congress, though, blocked the majority of Fair Deal legislation during Truman’s second term.

NATO and the Warsaw Pact

With the mandate from the election, Truman pushed ahead with his programs to defend Western Europe from possible attack. In 1949, the United States joined Great Britain, France, Italy, Canada, the Netherlands, Luxembourg, Belgium, Denmark, Norway, Iceland, and Portugal in forming a military alliance called the North Atlantic Treaty Organization (NATO). The NATO charter pledged that an attack on one of the member nations constituted an attack on all of the members. Greece and Turkey signed the treaty in 1952, followed by West Germany in 1955.

Perhaps the greatest significance of NATO was the fact that it committed the United States to Western Europe and prevented U.S. conservatives in the future from isolating the United States from the world as they had after World War I. Outraged and threatened, the USSR and the Soviet bloc countries it dominated in Eastern Europe made similar pledges of mutual defense.

The Fall of China

Meanwhile, events unfolding in China had enormous repercussions on the United States and ultimately on the Cold War itself. For decades, the Nationalist government of Chiang Kai-shek (sometimes written as Jiang Jieshi) had been fighting a long civil war against Communist rebels led by Mao Zedong (or Mao Tse-tung). The U.S. government under Roosevelt and Truman had backed the Nationalists with money and small arms shipments but overall had little influence on the war. Mao’s revolutionaries, however, finally managed to defeat government forces in 1949 and took control of mainland China.

While Chiang and his supporters fled to the island of Taiwan, Communist Party chairman Mao became the head of the new People’s Republic of China (PRC). The so-called fall of China was a crushing blow for the United States, primarily because it suddenly put more than a quarter of the world’s population under Communist control. Moreover, previous U.S. support for Chiang Kai-shek also meant that the PRC would not look favorably upon the United States.

The Arms Race

Also in 1949, Truman announced that the Soviet Union had successfully tested its first atomic bomb, sooner than American scientists had predicted. Even though it would have been difficult for the USSR to actually drop a nuclear bomb on U.S. soil—nuclear missiles would not be invented for another decade—the Soviets’ discovery cost Truman the diplomatic upper hand. Whereas the United States had lorded its nuclear superiority over the Soviets’ heads in the past, it could no longer do so.

To regain the upper hand, Truman poured federal dollars into the 1952 development of the hydrogen bomb, an even more devastating weapon than the original atomic bomb. Its developers feared this weapon would become a tool for genocide. The Soviet Union responded in kind with its own H-bomb the following year, ratcheting the stakes even higher. The United States and the USSR continued competing against each other with the development of greater and more destructive weapons in an arms race that lasted until the end of the Cold War.

The Second Red Scare

The fall of China, the Soviets’ development of nuclear weapons, and the crises in Europe all contributed to Americans’ growing fear of Communism at home. Remembering the Bolshevik revolutionaries’ cry for the global destruction of capitalism, frightened Americans began hunting for Communist revolutionaries within the United States and elsewhere. President Truman had already created the Loyalty Review Board in 1947 to investigate all federal departments, and the State Department in particular, to uncover any hidden Soviet agents working to overthrow the government. The board went into overdrive at the end of the decade, and thousands of innocent individuals were wrongfully accused and persecuted as a result.

Red Hunts

As a member of the House Un-American Activities Committee (HUAC), Congressman Richard M. Nixon of California helped spearhead the search for Communists in the government. In 1948, he prosecuted former federal employee and accused Communist Alger Hiss in one of the most dramatic cases of the decade. Hiss’s trial dragged on for two more years and ended with a five-year prison sentence for perjury. Prosecutors also charged husband and wife Julius and Ethel Rosenberg with having given American nuclear secrets to Soviet agents—an allegation that, though debated for decades after the trial, was corroborated by Soviet intelligence documents released in the 1990s. The Rosenbergs were convicted in 1951 and sent to the electric chair in 1953, becoming the first American civilians ever executed for espionage.

Although the Red hunts resulted in the capture of legitimate spies such as the Rosenbergs, Truman began to realize by the end of his presidency that the fear of Communism had caused widespread and undue panic. He tried to tame the Red-hunters in 1950 when he vetoed the McCarran Internal Security Bill, which he believed would give the U.S. president too much power to subvert civil liberties. Republicans in Congress, however, overrode Truman’s veto and passed the bill into law later that year.

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