History of the Korean War

United Nations Command (UNC) was established on July 7, 1950 following the United Nations' recognition of North Korean aggression against South Korea.  UNC signifies the world’s first attempt at collective security under the United Nations system. United Nations Security Council Resolutions 83 and 84 provided the international legal authority for member states to restore peace on the Korean Peninsula, and they designated the United States as the leader of the unified command we know as UN Command.  During the Korean War and the reconstruction period following the signing of the Armistice Agreement, twenty-two countries contributed either combat forces or medical assistance to support South Korea under the United Nations flag.



  • June 25, 1950:  North Korean forces crossed the 38th Parallel and invaded South Korea. The UN condemned the attack and passed United Nations Security Council Resolution (UNSCR) 82, calling for the cessation of hostilities and withdrawal of North Korean forces.
  • June 27, 1950:  United Nations Security Council Resolution (UNSCR) 83 declared North Korean actions constituted a breach of peace, recommending UN members provide assistance to South Korea to repel the attack and restore peace on the Korean Peninsula. 
  • June 28, 1950:  Seoul, South Korea’s capital city, was captured by North Korean forces.
  • July 7, 1950:  United Nations Security Council Resolution (UNSCR) 84 authorized the United States to establish and lead a unified command comprised of military forces from UN member states, and authorized that command to operate under the UN flag.
  • July 31, 1950:  United Nations Security Resolution (UNSCR) 85 called for UNC to determine the requirements for the relief to, and support for, the people of South Korea.
  • August 4—September 16, 1950: U.S. and South Korean troops established the "Busan Perimeter", and prevented North Korea from capturing South Korea.
  • September 15—16, 1950:  U.S. forces conducted the Incheon Landing.
  • September 16—22, 1950:  UNC forces broke out of the Busan Perimeter, recaptured Seoul, and advanced north into North Korea.
  • November 25, 1950:  The Chinese People’s Volunteer Army crossed the Yalu river into North Korea and drove back UNC forces. 
  • November 27—28, 1950:  UNC forces are surrounded at the Changjin (Chosin) Reservoir.
  • November 1950: United Nations Command incorporated the Civil Assistance sections of major combat units with the small UN Public Health and Welfare Detachment to form the UN Civil Assistance Command (UNCACK) in Busan. UNCACK supervised the distribution and utilization of more than $450 million in relief assistance from 33 UN member nations. UNCACK clothed, fed, housed, and medically treated millions before operations ceased in September 1953.
  • December 9—24, 1950:  Evacuation of UNC forces from the port city of Hungnam.  This operation also included the largest sea-borne military evacuation of civilians under combat conditions, transporting 98,000 Koreans from Hungnam, Wonsan, and Sonjin ports. 
  • January—April 1951:  Chinese People’s Volunteer Army pushed UNC forces back across the 38th Parallel and recaptured Seoul.
  • May 1951:  UNC counterattack freed Seoul. Fighting stalled around the 38th Parallel.
  • June 1951—July 1953:  UNC and communist forces fought sporadic battles for control of territory around the 38th Parallel.
  • July 10, 1951:  Peace talks began at Kaesong and eventually continued at Panmunjom.
  • July 27, 1953:  The Armistice Agreement was signed at Panmunjom, temporarily ending all fighting. A permanent peace treaty has never been signed.