On June 25, 1950, the North Korean army under Kim Il-sung invaded South Korea, starting the Korean War.
In the early weeks of the war, the North Koreans easily pushed back their southern counterparts.
Truman called for a naval blockade of Korea, only to learn that due to budget cutbacks, the U.S. Navy could not enforce such a measure.
Truman promptly urged the United Nations to intervene; it did, authorizing troops under the UN flag led by U.S. General Douglas MacArthur.
Truman decided he did not need formal authorization from Congress, believing that most legislators supported his position; this would come back to haunt him later, when the stalemated conflict was dubbed "Mr. Truman's War" by legislators.

However, on July 3, 1950, Truman did give Senate Majority Leader Scott W. Lucas a draft resolution titled "Joint Resolution Expressing Approval of the Action Taken in Korea".
Lucas stated Congress supported the use of force, the formal resolution would pass but was unnecessary, and consensus in Congress was to acquiesce.
Truman responded he did not want "to appear to be trying to get around Congress and use extra-Constitutional powers," and added that it was "up to Congress whether such a resolution should be introduced."

By August 1950, U.S. troops pouring into South Korea under UN auspices were able to stabilize the situation.
Responding to criticism over readiness, Truman fired his secretary of defense, Louis A. Johnson, replacing him with the retired General Marshall.
With UN approval, Truman decided on a "rollback" policy—conquest of North Korea.
UN forces led by General Douglas MacArthur led the counterattack, scoring a stunning surprise victory with an amphibious landing at the Battle of Inchon that nearly trapped the invaders.
UN forces marched north, toward the Yalu River boundary with China, with the goal of reuniting Korea under UN auspices.

However, China surprised the UN forces with a large-scale invasion in November.
The UN forces were forced back to below the 38th parallel, then recovered.
By early 1951 the war became a fierce stalemate at about the 38th parallel where it had begun.
Truman rejected MacArthur's request to attack Chinese supply bases north of the Yalu, but MacArthur promoted his plan to Republican house leader Joseph Martin, who leaked it to the press.
Truman was gravely concerned further escalation of the war might lead to open conflict with the Soviet Union, which was already supplying weapons and providing warplanes (with Korean markings and Soviet aircrew).
Therefore, on April 11, 1951, Truman fired MacArthur from his commands.

The dismissal of General Douglas MacArthur was among the least politically popular decisions in presidential history.
Truman's approval ratings plummeted, and he faced calls for his impeachment from, among others, Senator Robert A. Taft.
Fierce criticism from virtually all quarters accused Truman of refusing to shoulder the blame for a war gone sour and blaming his generals instead.
Others, including Eleanor Roosevelt, supported and applauded Truman's decision.
MacArthur meanwhile returned to the United States to a hero's welcome, and addressed a joint session of Congress, a speech the president called "a bunch of damn bullshit."

Truman and his generals considered the use of nuclear weapons against the Chinese army, but ultimately chose not to escalate the war to a nuclear level.
The war remained a frustrating stalemate for two years, with over 30,000 Americans killed, until an armistice ended the fighting in 1953.
In February 1952, Truman's approval mark stood at 22 percent according to Gallup polls, which is the all-time lowest approval mark for an active U.S. president, though it was matched by Richard Nixon in 1974.
On June 25, 1950, the North Korean army under Kim Il-sung invaded South Korea, starting the Korean War. In the early weeks of the war, the North Koreans easily pushed back their southern counterparts. Truman called for a naval blockade of Korea, only to learn that due to budget cutbacks, the U.S. Navy could not enforce such a measure. Truman promptly urged the United Nations to intervene; it did, authorizing troops under the UN flag led by U.S. General Douglas MacArthur. Truman decided he did not need formal authorization from Congress, believing that most legislators supported his position; this would come back to haunt him later, when the stalemated conflict was dubbed "Mr. Truman's War" by legislators.
However, on July 3, 1950, Truman did give Senate Majority Leader Scott W. Lucas a draft resolution titled "Joint Resolution Expressing Approval of the Action Taken in Korea". Lucas stated Congress supported the use of force, the formal resolution would pass but was unnecessary, and consensus in Congress was to acquiesce. Truman responded he did not want "to appear to be trying to get around Congress and use extra-Constitutional powers," and added that it was "up to Congress whether such a resolution should be introduced."
By August 1950, U.S. troops pouring into South Korea under UN auspices were able to stabilize the situation. Responding to criticism over readiness, Truman fired his secretary of defense, Louis A. Johnson, replacing him with the retired General Marshall. With UN approval, Truman decided on a "rollback" policy—conquest of North Korea. UN forces led by General Douglas MacArthur led the counterattack, scoring a stunning surprise victory with an amphibious landing at the Battle of Inchon that nearly trapped the invaders. UN forces marched north, toward the Yalu River boundary with China, with the goal of reuniting Korea under UN auspices.
However, China surprised the UN forces with a large-scale invasion in November. The UN forces were forced back to below the 38th parallel, then recovered. By early 1951 the war became a fierce stalemate at about the 38th parallel where it had begun. Truman rejected MacArthur's request to attack Chinese supply bases north of the Yalu, but MacArthur promoted his plan to Republican house leader Joseph Martin, who leaked it to the press. Truman was gravely concerned further escalation of the war might lead to open conflict with the Soviet Union, which was already supplying weapons and providing warplanes (with Korean markings and Soviet aircrew). Therefore, on April 11, 1951, Truman fired MacArthur from his commands.
The dismissal of General Douglas MacArthur was among the least politically popular decisions in presidential history. Truman's approval ratings plummeted, and he faced calls for his impeachment from, among others, Senator Robert A. Taft. Fierce criticism from virtually all quarters accused Truman of refusing to shoulder the blame for a war gone sour and blaming his generals instead. Others, including Eleanor Roosevelt, supported and applauded Truman's decision. MacArthur meanwhile returned to the United States to a hero's welcome, and addressed a joint session of Congress, a speech the president called "a bunch of damn bullshit."
Truman and his generals considered the use of nuclear weapons against the Chinese army, but ultimately chose not to escalate the war to a nuclear level. The war remained a frustrating stalemate for two years, with over 30,000 Americans killed, until an armistice ended the fighting in 1953. In February 1952, Truman's approval mark stood at 22 percent according to Gallup polls, which is the all-time lowest approval mark for an active U.S. president, though it was matched by Richard Nixon in 1974.
Harry S. Truman