Korea was ruled by Japan until the end of World War II when the Soviet Union liberated Korea north of the 38th parallel. The United States then liberated the South. In 1948 Korea was officially split into North and South Korea both with separate governments and both governments claiming to be the true government of all Korea. Neither government accepted the border of the 38th parallel. On June 25th, 1950 with the support of the Soviet Union and China, North Korea invaded South Korea with the goal of uniting the country. Twenty-one countries came to the aid of South Korea with the United States providing 88% of the troops deployed by the UN.
At first North Korea had the upper hand, continuously pushing back the South Korean forces. The city of Seoul would change hands 4 times over the course of the conflict as the two sides continued to push back and forth over the front lines as both China, the Soviet Union and the United States increased forces to try and get the upper hand. For the last two years of the conflict the war became one of attrition as the two sides fought over a front line that was not far from the 38th parallel. While the war on the ground failed to progress the war in the air was no contest. The Korean War was the first time jet fighters faced each other in air to air combat and the United States dominated over the Soviets. The fighting continued until an armistice was declared on July 27th, 1953.
The three years of the war were devastating to the new countries and the soldiers that fought on each side. More than 1 million people lost their lives, most of them being North and South Koreans. However more than 33,000 Americans and over 110,000 Chinese also died in the fighting. Some estimates put the civilian deaths at over 2 million and the military deaths at up to 1 million.