In the meantime, the communists had built a formidable political and military structure in North Korea under the aegis of the Soviet command. They had created a regional Five-Province Administrative Bureau in October 1945, which was reorganized into the North Korean Provisional People's Committee in February 1946 and shed the "Provisional" component of its name twelve months later. The communists also expanded and consolidated their party's strength by merging all of the left-wing groups into the North Korean Workers' Party in August 1946. Beginning in 1946, the armed forces also were organized and reinforced. Between 1946 and 1949, large numbers of North Korean youths--at least 10,000--were taken to the Soviet Union for military training. A draft was instituted, and in 1949 two divisions--40,000 troops--of the former Korean Volunteer Army in China, who had trained under the Chinese communists, and had participated in the Chinese civil war (1945-49), returned to North Korea.

By June 1950, North Korean forces numbered between 150,000 and 200,000 troops, organized into ten infantry divisions, one tank division, and one air force division. Soviet equipment, including automatic weapons of various types, T-34 tanks, and Yak fighter planes, had also been pouring into North Korea in early 1950. These forces were to fight the ill-equipped South Korean army of less than 100,000 men--an army lacking in tanks, heavy artillery, and combat airplanes, plus a coast guard of 4,000 men and a police force of 45,000 men.

The events following the June 1950 invasion proved the superiority of North Korean military forces and the soundness of their overall invasion strategy. South Korea's army was simply overwhelmed Seoul fell within three days. By early August, South Korean forces were confined in the southeastern corner of the peninsula to a territory 140 kilometers long and 90 kilometers wide. The rest of the territory was completely in the hands of the North Korean army.

The only unforeseen event complicating North Korea's strategy was the swift decision by the United States to commit forces in support of South Korea. On June 26, 1950, Truman ordered the use of United States planes and naval vessels against North Korean forces, and on June 30 United States ground troops were dispatched. The United States, fearing that inaction in Korea would be interpreted as appeasement of communist aggression elsewhere in the world, was determined that South Korea should not be overwhelmed and asked the UN Security Council to intervene. When Douglas MacArthur, the commanding general of the United Nations forces in Korea, launched his amphibious attack and landed at Inch'on on September 15, the course of the war changed abruptly. Within weeks much of North Korea was taken by United States and South Korean forces before Chinese "volunteers" intervened in October, enabling North Korea to eventually restore its authority over its domain. The war lasted until July 27, 1953, when a cease-fire agreement was signed at P'anmunjom. By then, the war had involved China and the Soviet Union, which had dispatc87a tched air force divisions to Manchuria in support of North Korea and had furnished the Chinese and North Koreans with arms, tanks, military supplies, fuel, foodstuffs, and medicine. Fifteen member-nations of the United Nations had contributed armed forces and medical units to South Korea.

The war left indelible marks on the Korean Peninsula and the world surrounding it. The entire peninsula was reduced to rubble casualties on both sides were enormous. The chances for peaceful unification had been remote even before 1950, but the war dashed all such hopes. Sizable numbers of South Koreans who either had been sympathetic or indifferent to communism before the war became avowed anticommunists afterwards. The war also intensified hostilities between the communist and noncommunist camps in the accelerating East-West arms race. Moreover, a large number of Chinese volunteer troops remained in North Korea until October 1958, and China began to play an increasingly important role in Korean affairs. Because tension on the Korean Peninsula remained high, the United States continued to station troops in South Korea, over the strenuous objections of North Korean leaders. The war also spurred Japan's industrial recovery and the United States' decision to rearm Japan.

Data as of June 1990