Korean War, Entry Into (1950)

Beginning of the first armed conflict of the Cold War period. In June 1950, U.S. President Harry S. Truman ordered U.S. military intervention in Korea to prevent the Communist People's Democratic Republic of Korea (North Korea) from taking control of the free Republic of Korea (South Korea).

At the end of World War II, following the surrender of Japan in August 1945, the United States and the Soviet Union agreed to divide Korea into two occupation zones. The Soviet Union occupied the Korean peninsula north of the 38th parallel, whereas the United States sent its troops to South Korea, south of the demarcation line. The Soviets planted a communist regime in North Korea, led by Kim Il Sung, a Korean nationalist determined to unify the country.

Right-wing Korean nationalist Syngman Rhee, leader of the exiled Korean government during World War II, traveled to Washington, DC, in 1946 to gain support for his plan to rule South Korea and eventually reunite the country. The United States agreed to back Rhee because it believed that he and his supporters were powerful enough to repel the North Koreans.

From 1946 to 1949, severe civil unrest between procommunist forces and right-wing elements left South Korea in chaos and resulted in a guerrilla war that caused the deaths of approximately 100,000 Koreans. The United Nations, strongly supported by the United States, monitored an election in South Korea in May 1948 to determine its government—a move the United States hoped would settle the unrest. The United Nations proposed having elections in North Korea as well, but the Soviets refused to participate, and none were held there.

On August 15, 1948, the Republic of Korea was formed to act as the government of South Korea, with Syngman Rhee as its leader. One month after the Soviet Union established the People's Democratic Republic of Korea in North Korea in September 1948, the Soviets removed their troops from the peninsula. The following June (1949), the United States followed suit and withdrew its troops as well.

All through 1949, Kim Il Sung appealed to Soviet leader Josef Stalin for arms and support. Finally, in the early months of 1950, Stalin agreed to provide tanks, artillery, and air power to help the North Koreans attack the South, with the expectation that the newly established People's Republic of China (PRC), under the communist leadership of Mao Zedong, would provide troop support for the North Koreans.

In the late 1940s, U.S. foreign policy was largely focused on the precarious situation in Europe. U.S. president Harry S. Truman and his advisers expected that war might erupt at any moment over the crisis in Berlin. In January 1950, Secretary of State Dean Acheson publicly stated that South Korea was not among the nations that the United States planned to defend against Soviet aggression.

With the opening of Soviet government archives to scholars in the 1990s, it is now known that Stalin based his decision to support the North Koreans on the belief that the United States would not become involved in Korea. Although the United States had misgivings about its stance on South Korea before the North Korean invasion in June 1950, after the attack occurred, the United States dramatically shifted its policy toward the defense of South Korea.

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