The Allies had divided Korea along the 38th parallel after liberating it from Japan at the end of World War II. The Soviet Union accepted Japanese surrender north of the 38th parallel. The United States accepted the Japanese surrender south of the 38th parallel.
As the Cold War escalated, the dividing line became more rigid. The United States and the Soviet Union set up governments in their occupation zones and continued to support each of the separate Korean governments.
In June 1950, North Korean troops crossed the 38th parallel, began attacking southward and overran Seoul. The war began with about 200,000 North Koreans fighting about 100,000 South Koreans.
A United Nations resolution stated North Korea was the aggressor. The U.N. demanded North Korea’s immediate withdrawal. This demand was not met.
A combined United Nations military effort with U.S. Army Gen. Douglas MacArthur in command was sent to halt the progress of North Korea. President Harry Truman quickly committed American forces to this United Nations military effort. Truman did not seek a formal declaration of war from Congress.
Sixteen U.N. nations supplied fighting units and five sent military hospitals and field ambulances. Australia was one of the first to contribute military personnel from all three services. The single largest U.N. contributor was the United States, and the next largest contributors of military forces were Great Britain, Australia and Canada. Other nations that sent fighting units were Belgium, Colombia, Ethiopia, France, Greece, Luxembourg, the Netherlands, New Zealand, Philippines, South Africa, Thailand and Turkey. Denmark, India, Italy, Norway and Sweden contributed military hospitals and field ambulances.
The war seesawed back and forth. U.S., U.N. and South Korean forces were initially pushed far to the south around the city of Pusan.
An amphibious landing Sept. 15, 1950, at Inchon, the port for the city of Seoul, drove the North Koreans back. U.N. military forces then pushed north, capturing Pyongyang in October 1950.
But, as fighting neared the Chinese border, China entered the war. Massive Chinese forces crossed the Yalu River. U.N. forces, largely American, retreated once again in bitter fighting.
With the arrival of the United Nations, and later the Chinese armies, there were a million combatants on the Korean peninsula one year after the war began. The Soviet Union’s contribution was always small and included medical units from Bulgaria, Czechoslovakia, Hungary, Poland and Romania.
The U.N. forces slowly recovered and fought their way back to the 38th parallel.
MacArthur then planned for a full-scale invasion of China. President Truman and others disagreed and wanted a limited war. MacArthur was dismissed and replaced by Gen. Matthew Ridgeway.
The war was then a bloody stalemate for the next two and a half years during ceasefire negotiations. The two sides finally reached an agreement in July 1953, during the first term of President Dwight Eisenhower.
By war’s end there were more than two million military personnel along the ceasefire line: 1,100,000 U.N. forces and South Koreans facing 1,200,000 North Koreans and Chinese.
The war left 33,742 American servicemen dead, 92,134 wounded, and 80,000 missing in action or prisoners of war.