Korean War - Background
Throughout most of its history, Korea has been invaded, influenced, and fought over by its larger neighbors. Korea's closed-door policy, adopted to ward off foreign encroachment, earned it the name of "Hermit Kingdom." Japanese, Chinese, and Russian competition in Northeast Asia led to armed conflict, and Japan defeated its two competitors and established dominance in Korea, formally annexing it in 1910. Japan remained firmly in control until the end of World War II. Near the end of the war, the April 1945 Yalta Conference agreed to establish a four-power trusteeship for Korea. With the unexpected early surrender of Japan, the United States proposed-and the Soviet Union agreed-that Japanese troops surrender to US forces south of the 38th parallel and to Soviet forces north of that line.
In 1948 two different governments were inaugurated on the Korean Peninsula, fixing the South-North division of Korea. The Republic of Korea (South Korea) was born south of the 38th parallel and the Democratic People's Republic of Korea (North Korea) north of it. North Korea, having obtained a massive amount of weapons from the Soviet Union and the Chinese Communist Party, launched guerrilla and other subversive operations against the South, preparing in haste to invade the South in a bid to communize the entire peninsula.
The communists 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.
The US military government tried to put together a moderate coalition to provide itself with a broad base of political support.But the July 1947 assassination of a prominent leftist in the coalition and the decision of a coalition moderate to enter into unification talks with the north led to the demise of the coalition efforts.
On August 15, 1948, the Republic of Korea (R.O.K.) was established. Syngman Rhee became the republic's first president. On September 9, 1948, the Democratic People's Republic of Korea (D.P.R.K.) was established in the north under Kim Il Sung. Guerrilla fighting in the south and clashes between southern and northern forces along the 38th parallel intensified during 1948-50. Although it continued to provide modest military aid to the south, the U.S. withdrew its occupation forces, leaving behind a 500-man Military Advisory Group by June 1949.
The communist South Korean Workers' Party led a partly indigenous guerrilla movement in the south after a major rebellion on Cheju Island in April 1948 that claimed tens of thousands of lives. South Korea's military and paramilitary forces were beset by mutinies and defections but eventually gained the upper hand. A communist-led revolt of army regiments in the southern part of the peninsula in October 1948, known as the Yosu-Sunch'on rebellion, consumed much of the army's attention and resources, and a massive purge in the aftermath of that revolt weakened the entire military establishment. In reaction to the Yosu-Sunch'on rebellion, a harsh national security law was passed in December 1949 that made communism a crime. However, the law was so comprehensive and vague that it could be used against any opposition group. Under the law, members of the South Korean Workers' Party were arrested and some 150,000 persons were barred from political activity.
North Korea put itself on a war footing in early 1949. Military officers were assigned to all high schools and higher institutions and all men and women aged 17 to 40 were given compulsory military training. Joint infantry, tank, and artillery field maneuvers were held by all major army units to test their ability to break through the 38th parallel.
North Korea's effort to win control of the south using guerrilla warfare forced South Korea's military leaders to concentrate on counterinsurgency operations. Fighting between South and North Korea began on 4 May 1949, in a battle probably started by the South. In the fall of 1949, North Korean guerrilla units attempted to gain control of remote areas and small towns in the mountainous areas of eastern and southern South Korea. It was estimated that as many as 5,000 guerrillas trained in North Korea were infiltrated into these areas by the winter of 1949. Two South Korean army divisions and one army brigade were quickly deployed to conduct sweep and destroy missions to eliminate the guerrillas. Counterinsurgency operations were initiated in South Cholla Province in October 1949. In some areas, South Korean villages were evacuated both to protect civilians and to assist counterinsurgency units in locating guerrilla bases. Guerrilla warfare continued until the end of 1949, coupled with skirmishing along the thirty-eighth parallel. By April 1950, less than 500 North Korean guerrillas remained in South Korea. Although the counterinsurgency program succeeded in ending the threat posed by the guerrillas, it had a deleterious effect on the army, necessitating reorganization and retraining for conventional war preparedness.
North Korea's conventional attack followed when it became clear that the insurgents would not triumph easily. At the beginning of 1950, more than 70 percent of North Korean troops were deployed in areas along the 38th parallel. By mid-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, with 210 fighter planes and 280 tanks. 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.
Despite the heightening of Cold War tensions, the Truman Administration originally did not expect a major military conflict, and it drastically downsized American forces from 1945 to 1950. Military planners, for their part, assumed that the next war would be similar to the Second World War (except that nuclear weapons would be used earlier on). The North Koreans took encouragement from the US policy which left Korea outside the US "defense line" in Asia, discounting the probability of American counteraction.
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