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.