President Harry Truman outlined a policy of "containment" in the doctrine that bears his name. The Truman Doctrine pledged to contain the Soviet Union's sphere of influence around the world, a policy that led to U.S. involvement in the Korean conflict—which President Truman is signing off on in this photo.
Photograph by U.S. Information Agency, courtesy National Archives

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  • On March 12, 1947, President Harry Truman delivered a speech in which he pledged financial and military support to the governments of Greece and Turkey, who were facing major internal conflict (in the case of Greece, an actual civil war). Truman’s reasons for supporting Greece and Turkey were at least in part to limit the political and military influence of the Soviet Union, which supported opposition parties. This policy of containment became known as the Truman Doctrine, and is often regarded as the start of the Cold War.
    In outlining his doctrine, Truman assumed that all local or national communist parties were aligned with, and influenced by, the Soviet Union. He warned that if one country in a region fell under the influence of Soviet communism, neighboring countries might also fall—the domino theory. By supporting the incumbent governments of Greece and Turkey, Truman said he was supporting European capitalism and democracy.
    Greece and Turkey both joined NATO, the Western military alliance, when it was created two years later. In the 1950s and 1960s, variations of the Truman Doctrine were used to support American involvement in Korea and Vietnam.
  • Term Part of Speech Definition Encyclopedic Entry
    align Verb

    to put in a straight line.

    alliance Noun

    people or groups united for a specific purpose.

    capitalism Noun

    economic system where the free exchange of goods and services is controlled by individuals and groups, not the state.

    civil war Noun

    conflict between groups in the same country or nation.

    Cold War Noun

    (1947-1991) conflict between the Soviet Union (and its allies) and the United States (and its allies). The two sides never confronted each other directly.

    communist Noun

    person or group of people who support communism, a type of economy where all property, including land, factories and companies, is held by the government.

    democracy Noun

    system of organization or government where the people decide policies or elect representatives to do so.

    domino theory Noun

    idea or belief that if one country is taken over or influenced by communism, the nearby nations will also be taken over one after another.

    financial Adjective

    having to do with money.

    government Noun

    system or order of a nation, state, or other political unit.

    incumbent Noun

    person currently holding an office or position.

    influence Verb

    to encourage or persuade a person or organization to act a certain way.

    military Noun

    armed forces.

    NATO Noun

    North Atlantic Treaty Organization. Military alliance of 28 North American and European countries.

    pledge Verb

    to guarantee or promise.

    political Adjective

    having to do with public policy, government, administration, or elected office.

    Soviet Union Noun

    (1922-1991) large northern Eurasian nation that had a communist government. Also called the Union of Soviet Socialist Republics, or the USSR.