“Police Action”: The Korean War, 1950-1953


In Europe, East and West eyed each other anxiously across the Iron Curtain. In Asia, the Cold War grew hot. In 1950, North Korean forces, armed mainly with Soviet weapons, invaded South Korea in an effort to reunite the peninsula under communist rule. Within the next couple of days the Truman administration and the United Nations had decided to aid in the defense of South Korea, and soon a multinational army had arrived under the command of General Douglas MacArthur. But while MacArthur was able to prevent the North Koreans from overrunning the South, an unexpected intervention by China soon turned the "police action" (as Truman called it) into a bloody stalemate. Differences between Truman and MacArthur led to the latter's firing in early 1951, and as the war ground on it grew more and more unpopular in the United States. Ultimately it would contribute to Dwight Eisenhower's election as president in 1952, and it would be the Eisenhower administration that brought an end to the conflict through a compromise peace.

This lesson will introduce students to the conflict by having them read the most important administration documents related to it. Specifically it will address four major issues:

1) Truman's decision to send troops to Korea
2) The decision to cross the 38th Parallel into North Korea, at the risk of a wider war with China
3) Truman's decision to fire MacArthur
4) The war's unpopularity in the United States.

The map below illustrates the progression of the conflict.

Guiding Question

  • Did the war in Korea represent a triumph or a failure of American foreign policy?

Learning Objectives

After completing this lesson, you should be able to:
  • Explain why the United States became involved in the war in Korea
  • Assess the decision to send U.S. and U.N. forces across the 38th Parallel into North Korea
  • Discuss the conflict between Truman and MacArthur, culminating in the latter's dismissal from command
  • Articulate the reasons why the war became unpopular in the United States
  • Identify on a world map foreign countries associated with the Korean War
  • Identify key terms and individuals associated with the Korean War

Suggested Activities

Task 1 - The Decision to Interveve in Korea
Task 2 - The Decision to Cross the 38th Parallel
Task 3 - Truman vs. MacArthur (not assigned)
Task 4 - Public Opinion and the Korean War

The Decision to Intervene in Korea:

You should have at least a basic understanding of America's Cold War foreign policy before tackling this lesson.

Remember these points of view?

George Kennan's influential article "The Sources of Soviet Conduct," which appeared in the July 1947 issue of Foreign Affairs:
....[I]t is clear that the main element of any United States policy toward the Soviet Union must be that of long-term, patient but firm and vigilant containment of Russian expansive tendencies.

1947 Truman Doctrine speech:
I believe that it must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures. I believe that we must assist free peoples to work out their own destinies in their own way.

Consult this interactive timeline. <-- Use this interactive timeline to include key events from the time period on your hard copy. Please choose the 3-5 most important events for each year listed.

After going over the key events leading up to the Korean War, you should read the following telegram from the U.S. State Department to President Truman regarding reports of North Korean forces invading the Republic of Korea:

Check out the following map, South Korea: UN Delay, Withdrawal, and Defense You'll have to zoom in on the map and look closely to understand its content.

Finally, you will read a series of documents— I know they are hard to read, so do your best to make sense of the them.

A) Resolution dated June 27, 1950, from United Nations Security Council recommending that the members of the United Nations furnish assistance to the Republic of Korea in order to repel the attack and restore peace and security in Korea:

B) Statement, dated June 27, 1950, by President Harry S. Truman, announcing his order to send U.S. air and naval forces to help defend South Korea and explaining the rationale for his decision:

C) Excerpts from the Radio and Television Address by President Harry S. Truman on the Situation in Korea, July 19, 1950

Using the above readings, plus what you have already learned in class about the origins and outbreak of the Korean War, write as homework a three-paragraph letter to the editor in which they defend Truman's decision to commit U.S. forces to the defense of South Korea. Each paragraph should consist of a general statement as well as at least two facts, drawn from the documents, to back up that statement. (12 points)

Korean War Mapping Exercise

Using the outline map provided (printable .pdf available here http://bedfordstmartins.com/mapcentral/om/pdfs/Korea1950.pdf) label the following items: China, Japan, USSR, Manchuria, North Korea, South Korea, Yalu River, Yellow Sea, Sea of Japan, 38th parallel, Armistice Line, Seoul, Pyongyang, Inchon, and Pusan. Also indicate the farthest North Korean advance (September 1950), the farthest UN advance (November 1950) and the farthest retreat of UN forces by January 1951.

The following sites maps are simple but informative: http://www.pbs.org/wgbh/amex/macarthur/maps/koreatxt.html

The Decision to Cross the 38th Parallel:

In this activity you will read documents pertaining to the decision to cross the 38th Parallel and enter North Korea; i.e., the decision to change the object of war from the defense of South Korea to the punishment of North Korea.

First, read about the landing at Inchon, which threw North Korean forces on the defensive and ultimately pushed them back into their own country. Do this by visiting the interactive timeline and in the "East Asia" section under 1950 click on the line that says "U.S. Forces Land at Inchon." After reading this consult a map of Korea in October 1950, which shows the progress of United Nations forces in the weeks following Inchon.

Once you have familiarized yourself with the overall military situation—that is, the rapid advance of UN forces and the retreat of the North Korean Army—you should read excerpts from the following documents, available at the Truman Presidential Library and Teaching American History. As you do so, complete the worksheet with tables listing both the reasons for crossing the 38th Parallel, and for not doing so.

Memorandum from George Kennan to Secretary of State Dean Acheson, August 23, 1950:

Excerpts from a Report to the President by the National Security Council on United States Courses of Action with Respect to Korea (NSC 81/1), September 9, 1950:

Excerpts from CIA Report on the Likelihood of Soviet or Chinese intervention in the event of an invasion of North Korea, September 27, 1950:

Resolution Adopted by the United Nations General Assembly, October 7, 1950:

Excerpt from Broadcast on Radio Peking, October 10, 1950:

Depending on how much class time is available, these documents could either be read individually or orally as a group. After students have finished reading the documents and completing the chart, students may pair off and go over their chart with a partner. Students should create a group list that will be shared with the entire class.

Truman vs. MacArthur

In the third activity you will be introduced to the conflict between President Truman and General MacArthur, which culminated in the General's dismissal from command in April 1951. Begin by listening to the following radio news bulletin announcing that MacArthur has been fired (it is quite brief—37 seconds).

Now read background information about the stormy relationship between the two men. Begin by returning to the interactive timeline, and under "East Asia" and "1950" click on "Meeting on Wake Island between Truman and MacArthur" and "Chinese Troops Enter North Korea" and reading the text that appears. Then under "1951" they should click on "Truman Dismisses MacArthur from Command" and do the same.

The following links will provide a greater understanding of the confrontation that developed between the President and his general.
Harry S. Truman, Speech Explaining the Firing of MacArthur, April 13, 1951:
General Douglas MacArthur Defends His Conduct in the War in Korea, April 19, 1951:

Order from President Truman, December 20, 1950:
Letter, MacArthur to Rep. Joseph Martin (R-MA), March 20, 1951:

You will now write a letter from the perspective of either President Truman or General MacArthur and justify the actions that were taken. Remember to "stay in character" as you defend "your" actions during the Korean War.

Public Opinion and the Korean War:
Finally, the fourth activity will address the war's unpopularity at home. Students will look at the results of public opinion polls taken in late 1952 and early 1953, excerpts from Eisenhower's famous "I will go to Korea" campaign speech, and a map illustrating how the war had resulted in stalemate by the end of 1951. All of these resources may be found on the sites of the Truman and Eisenhower libraries.

Presidential candidate Dwight D. Eisenhower makes 1952 campaign pledge, "I shall go to Korea":
Public opinion on the Korean War, 1953:
Map Showing Stalemate in Korea, November 1951—July 1953:

Drawing on these documents, in addition to what you have already learned about the Korean War, write a brief three paragraph essay in response to the following question: "What did the American public think about the war by late 1952—early 1953? What factors do you think influenced their opinions?"


After completing this lesson, students should be able to answer the following questions:
  • What factors influenced Truman's decision to commit U.S. forces to the defense of South Korea?
  • Analyze the significance of Truman's decision to allow MacArthur to cross the 38th Parallel. Why was this decision important?
  • Why did Truman fire MacArthur? Do you believe that this decision was justified?
  • What factors made the war in Korea so unpopular by 1952?

For aome students it may be possible to collapse these questions into a single larger question: Did the war in Korea represent a triumph or a failure of American foreign policy?

Extending the Lesson

Students who want to learn more about combat conditions in Korea may want to visit the Rutgers Oral History Index, which includes the reminiscences of a wide variety of men who fought there.

Another excellent source of information to help students fill in the gaps is "Korea +50: No Longer Forgotten," a site sponsored jointly by the Truman and Eisenhower Presidential Libraries.