The war began on 25 June 1950 when North Korea invaded South Korea. The Korean War was a war between North Korea with the support of China and the Soviet Union and South Korea with the support of the United Nations, principally from the United States.
After the World War II had ended, Korea was divided two zones of occupation, the Soviets administered the northern half and the Americans administered the southern half. In 1948, two sovereign states were established as a result of geopolitical tensions of the Cold War between the Soviet Union and the United States.
A socialist state was established in the north and a capitalist state in the south. Both governments of the two new Korean states claimed to be the sole legitimate government of all of Korea, and neither accepted the border as permanent.
The conflict escalated into warfare when North Korean military forces crossed the border and advanced into South Korea on 25 June 1950.
The fighting ended on 27 July 1953, when the Korean Armistice Agreement was signed. The agreement created the Korean Demilitarized Zone to separate North and South Korea.