The Korean War was a war between North Korea and South Korea from 25 June 1950 to 27 July 1953. It began as an attempt by North Korean supreme leader Kim Il-sung to unify Korea under his communist regime through military force. Two powers entered the war, with the United States under President Truman fighting alongside the South and the newly established People's Republic of China fighting alongside the North.
In 1910, Japan annexed Korea, where it ruled for 35 years until its surrender at the end of World War II on 15 August 1945. The United States and the Soviet Union divided Korea along the 38th parallel into two zones of occupation. The Soviets administered the northern zone and the Americans administered the southern zone. In 1948, as a result of Cold War tensions, the occupation zones became two sovereign states. A capitalist state, the First Republic of Korea, was established in the south under the authoritarian leadership of Syngman Rhee, and a socialist state, the Democratic People's Republic of Korea was established in the north under the totalitarian leadership of Kim Il-sung.