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Lesson Plan

The Korean War

About this Video

This six-minute video provides students with an introduction to the Korean War, including its context within the Cold War, and the hardships faced by American soldiers on the battlefield. Focusing on President Truman’s decision not to seek a formal Declaration of War from Congress, the video also sets up a discussion about the evolution and expansion of presidential war powers.

This video was featured in an online class on The Cold War in partnership with The Gilder Lehrman Institute’s History School and Joe Welch, a 2018 Gilder Lehrman National History Teacher of the Year and Master Teacher.


Students will learn about:

  • How North Korean’s invasion of South Korea in 1950 played into U.S. fears that the Soviet Union and Communist China were intent upon spreading communism across the globe.
  • Why President Harry Truman responded to the invasion by framing America’s participation in the war as a United Nations “police action” rather than asking Congress to issue a formal declaration of war.
  • How Truman’s decision to avoid the Constitutional process for declaring war through Congress has affected American politics and foreign policy ever since.
  • Social Studies
  • World History
  • U.S. History
  • 1950s America
  • America as a World Power
  • Cold War
  • Communism
  • Harry Truman
  • The Postwar Era (1945-1980)
  • U.S. Foreign Policy
  • Congress
For Teachers
Introducing the Lesson

During the Cold War, the U.S. practiced a policy of containment, working to stop the spread of communism in different parts of the world. So, on June 25, 1950, when the communist troops of North Korean poured across the 38th parallel to invade South Korea, U.S. President Harry S. Truman lost no time responding.

Following his foreign policy, known as the Truman Doctrine, which stated that the U.S. would provide support for countries threatened by the spread of communism, Truman and his administration moved fast to implement his doctrine of backing “free peoples” (in this case, the South Koreans) seeking to contain communist aggression (the invading North Koreans.) They feared the domino theory, that if one country fell to communism, the surrounding countries would follow.

Fearing a drawn-out debate in Congress, which had the sole power to declare war, Truman got help from the United Nations, which called on member nations to support South Korea.

Within days, the U.S. troops were leading a UN coalition into South Korea on what was officially called a “police action.”

However, it was increasingly clear over the next three years that the United States was engaged in a brutal war. Fierce battles raged up and down the mountainous, unforgiving terrain of the Korean peninsula, as the UN coalition struggled against an enemy force that ultimately included hundreds of thousands of communist Chinese troops as well.

The war ended in a stalemate, and the armistice that followed in 1953 essentially left North Korea divided from South Korea along the same pre-war border. But some three to four million were dead, including some 40,000 American soldiers.

By then, Truman was out of the Oval Office but his legacy of evading Congressional approval to commit U.S. troops in a “military action” set a deadly precedent, which continues to shape presidential calculations when engaging U.S. troops in conflicts around the globe.

Essential Questions
  • Why didn’t President Truman seek a formal Declaration of War from Congress?
  • How did Truman legally justify sending troops to Korea without a formal Declaration of War?
  • How did China’s decision to send troops to Korea affect the outcome of the war?
  • Why did some members of Congress believe that Truman should have first consulted them and sought a declaration of war before sending troops into harm’s way in Korea?
  • How has Truman’s decision not to seek a formal Declaration of War from Congress affected the power of an American president to wage war and commit troops to battle?
Lesson Procedure
  • Although the Constitution provides Congress alone with the power to “declare war,” the last U.S. President to ask and receive a formal Declaration of War from Congress was Franklin Roosevelt in 1941, when he committed troops to World War II. After Harry Truman declined to seek a formal Declaration of War in 1950, Presidents have generally followed his example. In your opinion, is this a positive or negative legacy of the Cold War? Does it benefit America for our Presidents to have greater flexibility and authority in committing US troops to battle? Or should Presidents be forced to obtain a formal Declaration of War through Congress?
  • How does the Korean War demonstrate both the rising importance of the US as a global power, as well as the limits of that power?
  • From 1950-53, about a million and a half American men were drafted into the US armed services, and about 1.3 million volunteered for service. Thousands of men and women worked as nurses or doctors in mobile hospital units. If you had been old enough and healthy enough for combat or medical service in the Korean War, would you have volunteered to do so? Why, or why not?
Additional Resources
Check out the Gilder Lehrman Institute’s History School Origins of the Cold War class Gilder Lehrman
Transcript for "How the Korean War Changed the Way the U.S. Goes to Battle" Retro Report

Integrate and evaluate multiple sources of information presented in diverse formats and media (e.g., visually, quantitatively, as well as in words) in order to address a question or solve a problem.

Analyze a complex set of ideas or sequences of events and explain how specific individuals, ideas, or events interact or develop over the course of a text.

Evaluate public policies in terms of intended and unintended outcomes, and related consequences.

Analyze multiple and complex causes and effect of events in the past.

Skill 3.A: Identify and describe a claim and/or argument in a non-text-based source.

Theme 6: America in the World (WOR).

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