June 25, 1950 - July 27, 1953 Conflict between Communist North and Democratic South Korea. This was also a proxy war between the United States and the Soviet Union. Principal combatants were North and South Korea, the United States and China although many nations sent troups under the aegis of the United Nations.
In initial stages of the war, North Korea troops overwhelmed South Korean and American forces and drove them to a small area in the far South around the city of Pusan. This became a desperate holding action called the Pusan Perimeter. American general Douglas MacArthur, as UN commander in chief for Korea, ordered a invasion far behind the North Korean troops at Inchon. United Nations troops drove the North Koreans back past the 38th parallel and continued on toward the Yalu River border of North Korea and China. This brought the Chinese into the war. The unexpected Chinese assualt repelled the United Nations troops back to the 38th parallel. The battle of Chosin Reservoir in winter was a terrible defeat for the United Nation troops, mainly American Marines. MacArthur was removed from command by President Harry S Truman in 1951. The rest of the war involved little territory changes and lenghty peace negotiations. A cease fire established a demilitarized zone (DMZ) around the 38th parallel which is still today defended by North Korean on one side and South Korean and American troops on the other. No peace treaty has yet been signed 50 years later.
Korea was officially a police action not a war in US parlance. US troops suffered about 50,000 fatalities, roughly equal to the Vietnam conflict but in a much shorter time. However later neglect of remembrance of this war in favor of the Vietnam War and World War II has caused the Korean War to be called the Forgotten War.
The movie and television series MASH was set in Korea.