The Cold War Begins
Containment, the Marshall Plan, and NATO divide the postwar world
Quick facts
- Truman Doctrine
- March 1947, containment of communism
- Marshall Plan
- Signed 1948, $13.3 billion for European recovery
- NATO founded
- 1949, collective defense alliance
- Rival
- The Soviet Union
What happened
The wartime alliance between the United States and the Soviet Union collapsed almost as soon as the fighting stopped, replaced by a global rivalry between capitalist democracy and Soviet communism. The United States adopted a policy of containment, aiming to stop the spread of communism. In the Truman Doctrine of March 1947, President Truman declared that it must be the policy of the United States to support free peoples resisting subjugation, and won aid for Greece and Turkey. In 1948 he signed the Marshall Plan, under which Congress appropriated $13.3 billion to rebuild the shattered economies of Western Europe. In 1949 the United States joined eleven other nations to form NATO, a military alliance built on the promise that an attack on one member would be treated as an attack on all.
Why it matters
The Cold War organized American foreign policy, military spending, and much of its domestic politics for more than four decades. Containment, foreign aid, and permanent alliances marked a decisive break from the isolationism of the interwar years and committed the United States to a leading role in the world. The rivalry drove the arms race, the space race, and proxy wars from Korea to Vietnam.
How we know
The Truman Doctrine speech and the Marshall Plan legislation survive in the National Archives, and the founding of NATO is documented in the North Atlantic Treaty and the diplomatic record of 1949.
Sources
- National Archives. Truman Doctrine (1947) · Primary source (author-declared)archives.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- National Archives. Marshall Plan (1948) · Primary source (author-declared)archives.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- North Atlantic Treaty Organization (NATO). The North Atlantic Treaty · Primary source (author-declared)nato.int · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- The Cold War → · This is the American opening of the Cold War; see the Cold War timeline for the full global rivalry, from Berlin and Korea to the missile crisis and beyond.