https://en.wikipedia.org/wiki/Korean_War



The Korean War (in South Korean Korean: 한국전쟁; Hanja: 韓國戰爭; RR: Hanguk Jeonjaeng, "Korean War"; in North Korean Korean: 조국해방전쟁; Hanja: 祖國解放戰爭; MR: Choguk haebang chŏnjaeng, "Fatherland: Liberation War"; 25 June 1950 – 27 July 1953) was a war between North Korea (with the support of China and the Soviet Union) and South Korea (with the support of the United Nations, with the principal support from the United States (US)). The war began on 25 June 1950 when North Korea invaded South Korea following a series of clashes along the border.

As a product of the Cold War between the Soviet Union and the United States, Korea had been split into two sovereign states in 1948 with the border set at the 38th parallel. A socialist state was established in the north under the communist leadership of Kim Il-sung and a capitalist state in the south under the anti-communist leadership of Syngman Rhee. Both governments of the two new Korean states claimed to be the sole legitimate government of all of Korea, and neither accepted the border as permanent. The conflict escalated into warfare when North Korean military (KPA) forces—supported by the Soviet Union and China—crossed the border and advanced into South Korea on 25 June 1950. The United Nations Security Council authorized the formation of the United Nations Command and the dispatch of forces to Korea to repel what was recognized as a North Korean invasion. Twenty-one countries of the United Nations eventually contributed to the UN force, with the United States providing around 90% of the military personnel.

After the first two months of war, the ill-equipped and underprepared South Korean Army (ROKA) and the US forces rapidly dispatched to Korea were on the point of defeat, forced back to a small area behind a defensive line known as the Pusan Perimeter. In September 1950, an amphibious UN counter-offensive was launched at Incheon, and cut off many KPA troops in South Korea. Those who escaped envelopment and capture were forced back north. UN forces invaded North Korea in October 1950 and moved rapidly towards the Yalu River—the border with China—but on 19 October 1950, Chinese forces of the People's Volunteer Army (PVA) crossed the Yalu and entered the war. The surprise Chinese intervention triggered a retreat of UN forces back below the 38th Parallel by late December.

In these and subsequent battles, Seoul changed hands four times, and the last two years of fighting became a war of attrition, with the front line close to the 38th Parallel. The war in the air, however, was never a stalemate. North Korea was subject to a massive bombing campaign. Jet fighters confronted each other in air-to-air combat for the first time in history, and Soviet pilots covertly flew in defense of their communist allies.

The fighting ended on 27 July 1953, when the Korean Armistice Agreement was signed. The agreement created the Korean Demilitarized Zone (DMZ) to separate North and South Korea, and allowed the return of prisoners. However, no peace treaty was ever signed, and according to some sources the two Koreas are technically still at war, engaged in a frozen conflict. In April 2018, the leaders of North and South Korea met at the DMZ and agreed to work towards a treaty to formally end the Korean War.

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Korea divided (1945–1949)

On 8 September 1945, US Lieutenant General John R. Hodge arrived in Incheon to accept the Japanese surrender south of the 38th Parallel. Appointed as military governor, Hodge directly controlled South Korea as head of the United States Army Military Government in Korea (USAMGIK 1945–48). He attempted to establish control by restoring Japanese colonial administrators to power, but in the face of Korean protests quickly reversed this decision. The USAMGIK refused to recognize the provisional government of the short-lived People's Republic of Korea (PRK) due to its suspected Communist sympathies.

In December 1945, Korea was administered by a US-Soviet Union Joint Commission, as agreed at the Moscow Conference, with the aim of granting independence after a five-year trusteeship. The idea was not popular among Koreans and riots broke out. To contain them, the USAMGIK banned strikes on 8 December 1945 and outlawed the PRK Revolutionary Government and the PRK People's Committees on 12 December 1945. Following further large-scale civilian unrest, the USAMGIK declared martial law.

Citing the inability of the Joint Commission to make progress, the US government decided to hold an election under United Nations auspices with the aim of creating an independent Korea. The Soviet authorities and the Korean Communists refused to co-operate on the grounds it would not be fair, and many South Korean politicians boycotted it. A general election was held in the South on 10 May 1948. North Korea held parliamentary elections three months later on 25 August.

The resultant South Korean government promulgated a national political constitution on 17 July 1948, and elected Syngman Rhee as President on 20 July 1948. The Republic of Korea (South Korea) was established on 15 August 1948. In the Soviet Korean Zone of Occupation, the Soviet Union established a communist government led by Kim Il-sung.

The Soviet Union withdrew as agreed from Korea in 1948, and US troops withdrew in 1949.

Chinese Civil War (1945–1949)
With the end of the war with Japan, the Chinese Civil War resumed in earnest between the Communists and Nationalists. While the Communists were struggling for supremacy in Manchuria, they were supported by the North Korean government with matériel and manpower. According to Chinese sources, the North Koreans donated 2,000 railway cars worth of supplies while thousands of Koreans served in the Chinese People's Liberation Army (PLA) during the war. North Korea also provided the Chinese Communists in Manchuria with a safe refuge for non-combatants and communications with the rest of China.

The North Korean contributions to the Chinese Communist victory were not forgotten after the creation of the People's Republic of China (PRC) in 1949. As a token of gratitude, between 50,000 and 70,000 Korean veterans that served in the PLA were sent back along with their weapons, and they later played a significant role in the initial invasion of South Korea. China promised to support the North Koreans in the event of a war against South Korea.

After the formation of the PRC, the PRC government named the Western nations, led by the US, as the biggest threat to its national security. Basing this judgment on China's century of humiliation beginning in the mid-19th century, US support for the Nationalists during the Chinese Civil War and the ideological struggles between revolutionaries and reactionaries, the PRC Chinese leadership believed that China would become a critical battleground in the US' crusade against Communism. As a countermeasure and to elevate China's standing among the worldwide Communist movements, the PRC leadership adopted a foreign policy that actively promoted Communist revolutions throughout territories on China's periphery.

Prelude to war (1950)
By 1949, South Korean forces had reduced the active number of communist guerrillas in the South from 5,000 to 1,000. However, Kim Il-sung believed that the guerrillas weakened the South Korean military and that a North Korean invasion would be welcomed by much of the South Korean population. Kim began seeking Stalin's support for an invasion in March 1949, traveling to Moscow to attempt to persuade him.

Serious border clashes between South and North occurred on 4 August 1949, when thousands of North Korean troops attacked South Korean troops occupying territory north of the 38th Parallel. The 2nd and 18th ROK Infantry Regiments repulsed initial attacks in Kuksa-bong (above the 38th Parallel) and Ch'ungmu, and at the end of the clashes ROK troops were "completely routed".

Stalin initially did not think the time was right for a war in Korea. PLA forces were still embroiled in the Chinese Civil War, while US forces remained stationed in South Korea. By spring 1950, he believed that the strategic situation had changed: PLA forces under Mao Zedong had secured final victory in China, US forces had withdrawn from Korea, and the Soviets detonated their first nuclear bomb, breaking the US atomic monopoly. As the US had not directly intervened to stop the communist victory in China, Stalin calculated that they would be even less willing to fight in Korea, which had much less strategic significance. The Soviets had also cracked the codes used by the US to communicate with their embassy in Moscow, and reading these dispatches convinced Stalin that Korea did not have the importance to the US that would warrant a nuclear confrontation. Stalin began a more aggressive strategy in Asia based on these developments, including promising economic and military aid to China through the Sino-Soviet Treaty of Friendship, Alliance, and Mutual Assistance.

In April 1950, Stalin gave Kim permission to invade the South under the condition that Mao would agree to send reinforcements if needed. Stalin made it clear that Soviet forces would not openly engage in combat, to avoid a direct war with the US. Kim met with Mao in May 1950. Mao was concerned the US would intervene but agreed to support the North Korean invasion. China desperately needed the economic and military aid promised by the Soviets. However, Mao sent more ethnic Korean PLA veterans to Korea and promised to move an army closer to the Korean border. Once Mao's commitment was secured, preparations for war accelerated.

Soviet generals with extensive combat experience from the Second World War were sent to North Korea as the Soviet Advisory Group. These generals completed the plans for the attack by May. The original plans called for a skirmish to be initiated in the Ongjin Peninsula on the west coast of Korea. The North Koreans would then launch a counterattack that would capture Seoul and encircle and destroy the ROK. The final stage would involve destroying South Korean government remnants and capturing the rest of South Korea, including the ports.

On 7 June 1950, Kim Il-sung called for a Korea-wide election on 5–8 August 1950 and a consultative conference in Haeju on 15–17 June 1950. On 11 June, the North sent three diplomats to the South as a peace overture that Rhee rejected outright. On 21 June, Kim Il-Sung revised his war plan to involve a general attack across the 38th Parallel, rather than a limited operation in the Ongjin Peninsula. Kim was concerned that South Korean agents had learned about the plans and that South Korean forces were strengthening their defenses. Stalin agreed to this change of plan.

While these preparations were underway in the North, there were frequent clashes along the 38th Parallel, especially at Kaesong and Ongjin, many initiated by the South. The ROK was being trained by the US Korean Military Advisory Group (KMAG). On the eve of war, KMAG commander General William Lynn Roberts voiced utmost confidence in the ROK and boasted that any North Korean invasion would merely provide "target practice". For his part, Syngman Rhee repeatedly expressed his desire to conquer the North, including when US diplomat John Foster Dulles visited Korea on 18 June.

Although some South Korean and US intelligence officers predicted an attack from the North, similar predictions were made before and nothing happened. The Central Intelligence Agency noted the southward movement by the KPA, but assessed this as a "defensive measure" and concluded an invasion was "unlikely". On 23 June, UN observers inspected the border and did not detect that war was imminent.

Comparison of forces
Throughout 1949 and 1950, the Soviets continued arming North Korea. After the Communist victory in the Chinese Civil War, ethnic Korean units in the PLA were released to North Korea. The combat veterans from China, the tanks, artillery and aircraft supplied by the Soviets, and rigorous training increased North Korea's military superiority over the South, armed by the US military with mostly small arms, but no heavy weaponry such as tanks.

According to the first official census in 1949 the population of North Korea numbered 9,620,000, and by mid-1950 North Korean forces numbered between 150,000 and 200,000 troops, organized into 10 infantry divisions, one tank division, and one air force division, with 210 fighter planes and 280 tanks, who captured scheduled objectives and territory, among them Kaesong, Chuncheon, Uijeongbu, and Ongjin. Their forces included 274 T-34-85 tanks, 200 artillery pieces, 110 attack bombers, and some 150 Yak fighter planes, and 35 reconnaissance aircraft. In addition to the invasion force, the North had 114 fighters, 78 bombers, 105 T-34-85 tanks, and some 30,000 soldiers stationed in reserve in North Korea. Although each navy consisted of only several small warships, the North and South Korean navies fought in the war as sea-borne artillery for their armies.

In contrast, the South Korean population totaled 20,188,641, and its army was unprepared and ill-equipped. As of 25 June 1950 the ROK had 98,000 soldiers (65,000 combat, 33,000 support), no tanks (they had been requested from the US military, but requests were denied), and a 22-plane air force comprising 12 liaison-type and 10 AT6 advanced-trainer airplanes. Large US garrisons and air forces were in Japan, but only 200–300 US troops were in Korea.

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