Korean War

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Korean War
Part of the
Korean War Montage 2.png

Clockwise from top:
Result Inconclusive

Korean Demilitarized Zone established

  • North Korea gains the city of Kaesong, but loses a net total of 3,900 km2 (1,506 sq mi), including the city of Sokcho, to South Korea.[15]
 South Korea  North Korea
Medical support:[5]
Commanders and leaders
Peak strength:

Together: 972,334

United States 1,780,000[24]
Peak strength:

Together: 1,742,000

China 2,970,000[29]
Soviet Union 72,000[28]
Casualties and losses
  • Total civilian deaths: 2–3 million (est.)[30][31]
  • South Koreans:
    990,968 total casualties[21]
  • North Koreans:
    1,550,000 total casualties (est.)[21]

The Korean War (also known by

rebellions in South Korea.[32][33][34] North Korea was supported by China and the Soviet Union while South Korea was supported by the United States and allied countries. The fighting ended with an armistice
on 27 July 1953.

In 1910,

Democratic People's Republic of Korea, was established in the north under the totalitarian communist leadership of Kim Il-sung, while a capitalist state, the Republic of Korea, was established in the south under the authoritarian, autocratic 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.

North Korean military (Korean People's Army, KPA) forces crossed the border and drove into South Korea on 25 June 1950.[35] Joseph Stalin had final decision power and several times demanded North Korea postpone the invasion, until he gave final approval in spring 1950.[36] The United Nations Security Council denounced the North Korean move as an invasion and authorized the formation of the United Nations Command and the dispatch of forces to Korea[37] to repel it.[38][39] The Soviet Union was boycotting the UN for recognizing Taiwan (Republic of China) as China,[40] and the People's Republic of China was not recognized by the UN, so neither could support their ally North Korea at the Security Council meeting. Twenty-one countries of the United Nations eventually contributed to the UN force, with the United States providing around 90% of the military personnel.[41]

After the first two months of war,

First Phase Offensive and the Second Phase Offensive
. Chinese forces were in South Korea by late December.

In these and subsequent battles,

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 the two Koreas are technically still at war, engaged in a frozen conflict.[42][43] In April 2018, the leaders of North and South Korea met at the DMZ[44] and agreed to work toward a treaty to end the Korean War formally.[45]

The Korean War was among the most destructive conflicts of the modern era, with approximately 3 million war fatalities and a larger proportional civilian death toll than World War II or the Vietnam War. It incurred the destruction of virtually all of Korea's major cities, thousands of massacres by both sides, including the mass killing of tens of thousands of suspected communists by the South Korean government, and the torture and starvation of prisoners of war by the North Koreans. North Korea became among the most heavily bombed countries in history.[46] 1.5 million North Koreans are estimated to have fled North Korea over the course of the war.[47]


Korean War
South Korean name
Hangul6·25 전쟁 or 한국 전쟁
Hanja六二五戰爭 or 韓國戰爭
North Korean name

In South Korea, the war is usually referred to as the "625 War" (6·25 전쟁; 六二五戰爭), the "625 Upheaval" (6·25 동란; 六二五動亂; yugio dongnan), or simply "625", reflecting the date of its commencement on 25 June.[48]

In North Korea, the war is officially referred to as the "Fatherland Liberation War" (Choguk haebang chŏnjaeng) or alternatively the "Chosŏn [Korean] War" (조선전쟁; Chosŏn chŏnjaeng).[49]

In mainland China, the segment of the war after the intervention of the People's Volunteer Army is most commonly and officially known as the "Resisting America and Assisting Korea War"[50] (Chinese: 抗美援朝战争; pinyin: Kàngměi Yuáncháo Zhànzhēng), although the term "Chosŏn War" (Chinese: 朝鮮戰爭; pinyin: Cháoxiǎn Zhànzhēng) is sometimes used unofficially. The term "Hán (Korean) War" (Chinese: 韓戰; pinyin: Hán Zhàn) is most commonly used in Taiwan (Republic of China), Hong Kong and Macau.

In the U.S., the war was initially described by President Harry S. Truman as a "police action", as the United States never formally declared war on its opponents and the operation was conducted under the auspices of the United Nations.[51] It has been sometimes referred to in the English-speaking world as "The Forgotten War" or "The Unknown War" because of the lack of public attention it received both during and after the war, relative to the global scale of World War II, which preceded it, and the subsequent angst of the Vietnam War, which succeeded it.[52][53]


Imperial Japanese rule (1910–1945)

Eulsa Treaty in 1905, then annexed it with the Japan–Korea Annexation Treaty in 1910. After that, the Korean Empire fell and Korea was directly ruled by Japan from 1910 to 1945.[55]


communists led internal and external warfare against the Japanese.[57][58]

In China, the nationalist

Burma Campaign (December 1941 – August 1945). The communists, led among others by Kim Il-sung, fought the Japanese in Korea and Manchuria.[59]

At the

Cairo Conference in November 1943, China, the United Kingdom and the United States all decided that "in due course Korea shall become free and independent".[60]

Korea divided (1945–1949)

At the Tehran Conference in November 1943 and the Yalta Conference in February 1945, the Soviet Union promised to join its allies in the Pacific War within three months of the victory in Europe. Germany officially surrendered on 8 May 1945, and the USSR declared war on Japan and invaded Manchuria on 8 August 1945, three months later. This was three days after the atomic bombing of Hiroshima.[58][61] By 10 August, the Red Army had begun to occupy the north of Korea.[62]

On the night of 10 August in Washington, U.S. Colonels Dean Rusk and Charles H. Bonesteel III were assigned to divide Korea into Soviet and U.S. occupation zones and proposed the 38th Parallel as the dividing line. This was incorporated into the U.S. General Order No. 1, which responded to the Japanese surrender on 15 August. Explaining the choice of the 38th Parallel, Rusk observed, "even though it was further north than could be realistically reached by U. S. [sic] forces in the event of Soviet disagreement ... we felt it important to include the capital of Korea in the area of responsibility of American troops". He noted that he was "faced with the scarcity of U.S. forces immediately available and time and space factors which would make it difficult to reach very far north before Soviet troops could enter the area".[63][64] As Rusk's comments indicate, the U.S. doubted whether the Soviet government would agree to this.[65][66][67][68] Soviet leader Joseph Stalin, however, maintained his wartime policy of co-operation, and on 16 August, the Red Army halted at the 38th Parallel for three weeks to await the arrival of U.S. forces in the south.[62]

On 7 September 1945, General Douglas MacArthur issued Proclamation No. 1 to the people of Korea, announcing U.S. military control over Korea south of the 38th parallel and establishing English as the official language during military control.[69]

On 8 September 1945, U.S. Lieutenant General John R. Hodge arrived in Incheon to accept the Japanese surrender south of the 38th Parallel.[66] Appointed as military governor, Hodge directly controlled South Korea as head of the United States Army Military Government in Korea (USAMGIK 1945–48).[70]

In December 1945, Korea was administered by a U.S.–Soviet Union Joint Commission, as agreed at the Moscow Conference, with the aim of granting independence after a five-year trusteeship.[71][72] The idea was not popular among Koreans and riots broke out.[55] 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.[73] Following further large-scale civilian unrest,[74] the USAMGIK declared martial law.

Citing the inability of the Joint Commission to make progress, the U.S. 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 that it would not be fair, and many South Korean politicians boycotted it.

general election was held in the South on 10 May 1948.[77][78] North Korea held parliamentary elections three months later on 25 August.[79]

The resultant South Korean government promulgated a national political constitution on 17 July 1948, and elected Syngman Rhee as President on 20 July 1948. This election is generally considered to have been manipulated by the Rhee regime. The Republic of Korea (South Korea) was established on 15 August 1948. In the Soviet Korean Zone of Occupation, the Soviet Union agreed to the establishment of a communist government[77] led by Kim Il-sung.[80]

The Soviet Union withdrew its forces from Korea in 1948, and U.S. troops withdrew in 1949.[81][82]

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.[83] According to Chinese sources, the North Koreans donated 2,000 railway cars worth of supplies while thousands of Koreans served in the Chinese PLA during the war.[84] North Korea also provided the Chinese Communists in Manchuria with a safe refuge for non-combatants and communications with the rest of China.[83]

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.[83] China promised to support the North Koreans in the event of a war against South Korea.[85]

After the formation of the PRC, the PRC government named the Western nations, led by the U.S., as the biggest threat to its national security.[86] Basing this judgment on multiple factors, including the idea of a Chinese century of humiliation at the hands of Western powers beginning in the mid-19th century,[87] U.S. support for the Nationalists during the Chinese Civil War,[88] and the ideological struggles between revolutionaries and reactionaries,[89] the PRC Chinese leadership believed that China would become a critical battleground in the U.S.' crusade against Communism.[90] 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.[91]

Communist insurgency in South Korea (1948–1950)

By 1948, a large-scale, North Korea-backed insurgency had broken out in the southern half of the peninsula. This was exacerbated by the ongoing undeclared border war between the Koreas, which saw division-level engagements and thousands of deaths on both sides.[92] The ROK in this time was almost entirely trained and focused on counterinsurgency, rather than conventional warfare. They were equipped and advised by a force of a few hundred American officers, who were largely successful in helping the ROKA to subdue guerrillas and hold its own against North Korean military (Korean People's Army, KPA) forces along the 38th parallel.[93] Approximately 8,000 South Korean soldiers and police died in the insurgent war and border clashes.[94]

The first socialist uprising occurred without direct North Korean participation, though the guerrillas still professed support for the northern government. Beginning in April 1948 on the isolated island of Jeju, the campaign saw mass arrests and repression by the South Korean government in the fight against the South Korean Labor Party, resulting in a total of 30,000 violent deaths, among them 14,373 civilians (of whom ~2,000 were killed by rebels and ~12,000 by ROK security forces). The Yeosu–Suncheon rebellion overlapped with it, as several thousand army defectors waving red flags massacred right-leaning families. This resulted in another brutal suppression by the government and between 2,976 and 3,392 deaths. By May 1949, both uprisings had been crushed.

Insurgency reignited in the spring of 1949 when attacks by guerrillas in the mountainous regions (buttressed by army defectors and North Korean agents) increased. Insurgent activity peaked in late 1949 as the ROKA engaged so-called People's Guerrilla Units. Organized and armed by the North Korean government, and backed up by 2,400 KPA commandos who had infiltrated through the border, these guerrillas launched a large offensive in September aimed at undermining the South Korean government and preparing the country for the KPA's arrival in force. This offensive failed.[95] However, by this point, the guerrillas were firmly entrenched in the Taebaek-san region of the North Gyeongsang Province (around Taegu), as well as in the border areas of the Gangwon Province.[96]

While the insurgency was ongoing, the ROKA and KPA engaged in multiple battalion-sized battles along the border, starting in May 1949.[93] Serious border clashes between South and North continued 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)[97] and Ch'ungmu,[citation needed] and at the end of the clashes ROK troops were "completely routed".[98] Border incidents decreased significantly by the start of 1950.[96]

Meanwhile, counterinsurgency efforts in the South Korean interior intensified; persistent operations, paired with worsening weather conditions, eventually denied the guerrillas sanctuary and wore away their fighting strength. North Korea responded by sending more troops to link up with existing insurgents and build more partisan cadres; the number of North Korean infiltrators had reached 3,000 soldiers in 12 units by the start of 1950, but all of these units were destroyed or scattered by the ROKA.

8th Division. The second battalion was annihilated by a two-battalion hammer-and-anvil maneuver by units of the ROKA 6th Division, resulting in a loss toll of 584 KPA guerrillas (480 killed, 104 captured) and 69 ROKA troops killed, plus 184 wounded.[100] By spring of 1950, guerrilla activity had mostly subsided; the border, too, was calm.[101]

Prelude to war (1950)

By 1949, South Korean and U.S. military actions had reduced the active number of indigenous communist guerrillas in the South from 5,000 to 1,000. However, Kim Il-sung believed that widespread uprisings had 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.[102]

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 U.S. forces remained stationed in South Korea.[103] By spring 1950, he believed that the strategic situation had changed: PLA forces under Mao Zedong had secured final victory in China, U.S. forces had withdrawn from Korea, and the Soviets had detonated their first nuclear bomb, breaking the U.S. atomic monopoly. As the U.S. 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 U.S. to communicate with their embassy in Moscow, and reading these dispatches convinced Stalin that Korea did not have the importance to the U.S. that would warrant a nuclear confrontation.[104] 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.[105]

In April 1950, Stalin gave Kim permission to attack the government in the South under the condition that Mao would agree to send reinforcements if needed. For Kim, this was the fulfillment of his goal to unite Korea after its division by foreign powers. Stalin made it clear that Soviet forces would not openly engage in combat, to avoid a direct war with the U.S.[106] Kim met with Mao in May 1950. Historical analyses regarding Mao's approval of Kim's plans differ.[107]: 28–9  Nikita Khrushchev's memoirs were long viewed as the most authoritative source, and Khrushchev wrote that Mao approved Kim's plans because Mao viewed the matter as one for the Korean people to decide for themselves.[107]: 29  Citing recent scholarship, Zhao Suisheng, writing in 2022, contends that Mao did not approve of Kim's plans in advance, opposing them over concerns that the U.S. would intervene and that China could be dragged into the conflict.[107]: 29  By some accounts, Mao agreed to support the North Korean invasion despite these concerns, as China desperately needed the economic and military aid promised by the Soviets.[108] However, Mao sent more ethnic Korean PLA veterans to Korea and promised to move an army closer to the Korean border.[109] Once Mao's commitment was secured, preparations for war accelerated.[110][111]

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.[112] 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.[113]

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 which Rhee rejected outright.[106] 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.[114]

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.[33][34] The ROK was being trained by the U.S. 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".[115] For his part, Syngman Rhee repeatedly expressed his desire to conquer the North, including when U.S. diplomat John Foster Dulles visited Korea on 18 June.[116]

Although some South Korean and U.S. intelligence officers predicted an attack from the North, similar predictions had been made before and nothing had happened.[117] The Central Intelligence Agency noted the southward movement by the KPA, but assessed this as a "defensive measure" and concluded an invasion was "unlikely".[118] On 23 June, UN observers inspected the border and did not detect that war was imminent.[119]

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 sent to North Korea.

small arms, but no heavy weaponry such as tanks.[122] While older histories of the conflict often referred to these ethnic Korean PLA veterans as being sent from northern Korea to fight in the Chinese Civil War before being sent back, recent Chinese archival sources studied by Kim Donggill indicate that this was not the case. Rather, the soldiers were indigenous to China (part of China's longstanding ethnic Korean community) and were recruited to the PLA in the same way as any other Chinese citizen.[123]

According to the first official census in 1949, the population of North Korea numbered 9,620,000,[124] 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.[66] Although each navy consisted of only several small warships, the North and South Korean navies fought in the war as seaborne artillery for their armies.

In contrast, the South Korean population was estimated at 20 million

AT-6 advanced-trainer airplanes. Large U.S. garrisons and air forces were in Japan,[126] but only 200–300 U.S. troops were in Korea.[127]

Course of the war

At dawn on Sunday, 25 June 1950, the KPA crossed the 38th Parallel behind artillery fire.[128] The KPA justified its assault with the claim that ROK troops attacked first and that the KPA were aiming to arrest and execute the "bandit traitor Syngman Rhee".[129] Fighting began on the strategic Ongjin Peninsula in the west.[130][131] There were initial South Korean claims that the 17th Regiment captured the city of Haeju, and this sequence of events has led some scholars to argue that the South Koreans fired first.[130][132]

Whoever fired the first shots in Ongjin, KPA forces attacked all along the 38th Parallel within an hour. The KPA had a combined arms force including tanks supported by heavy artillery. The ROK had no tanks, anti-tank weapons or heavy artillery to stop such an attack. In addition, the South Koreans committed their forces in a piecemeal fashion and these were routed in a few days.[133]

On 27 June, Rhee evacuated from Seoul with some of the government. On 28 June, at 2 am, the ROK blew up the Hangang Bridge across the Han River in an attempt to stop the KPA. The bridge was detonated while 4,000 refugees were crossing it and hundreds were killed.[134][135] Destroying the bridge also trapped many ROK units north of the Han River.[133] In spite of such desperate measures, Seoul fell that same day. A number of South Korean National Assemblymen remained in Seoul when it fell, and forty-eight subsequently pledged allegiance to the North.[136]

On 28 June, Rhee ordered the massacre of suspected political opponents in his own country.[137]

In five days, the ROK, which had 95,000 troops on 25 June, was down to less than 22,000 troops. In early July, when U.S. forces arrived, what was left of the ROK were placed under U.S. operational command of the United Nations Command.[138]

Factors in U.S. intervention

The Truman administration was unprepared for the invasion. Korea was not included in the strategic Asian Defense Perimeter outlined by United States Secretary of State Dean Acheson.[139] Truman himself was at his home in Independence, Missouri.[140] Military strategists were more concerned with the security of Europe against the Soviet Union than East Asia.[141] At the same time, the administration was worried that a war in Korea could quickly escalate without American intervention. Said diplomat John Foster Dulles in a cable: "To sit by while Korea is overrun by unprovoked armed attack would start a disastrous chain of events leading most probably to world war."[142]

While there was initial hesitance by some in the U.S. government to get involved in the war, considerations about Japan played a part in the ultimate decision to engage on behalf of South Korea. Especially after the fall of China to the Communists, U.S. experts on East Asia saw Japan as the critical counterweight to the Soviet Union and China in the region. While there was no U.S. policy dealing with South Korea directly as a national interest, its proximity to Japan increased the importance of South Korea. Said Kim: "The recognition that the security of Japan required a non-hostile Korea led directly to President Truman's decision to intervene ... The essential point ... is that the American response to the North Korean attack stemmed from considerations of U.S. policy toward Japan."[143][144]

Another major consideration was the possible Soviet reaction if the U.S. intervened. The Truman administration was fearful that a war in Korea was a diversionary assault that would escalate to a general war in Europe once the United States committed in Korea. At the same time, "[t]here was no suggestion from anyone that the United Nations or the United States could back away from [the conflict]".

Tito-Stalin Split—was vital to the defense of Italy and Greece, and the country was first on the list of the National Security Council's post-North Korea invasion list of "chief danger spots".[146] Truman believed if aggression went unchecked, a chain reaction would be initiated that would marginalize the UN and encourage Communist aggression elsewhere. The UN Security Council approved the use of force to help the South Koreans, and the U.S. immediately began using air and naval forces that were in the area to that end. The Truman administration still refrained from committing troops on the ground because some advisers believed the North Koreans could be stopped by air and naval power alone.[147]

The Truman administration was still uncertain if the attack was a ploy by the Soviet Union or just a test of U.S. resolve. The decision to commit ground troops became viable when a communiqué was received on 27 June indicating the Soviet Union would not move against U.S. forces in Korea.[148] The Truman administration now believed it could intervene in Korea without undermining its commitments elsewhere.

United Nations Security Council Resolutions

On 25 June 1950, the United Nations Security Council unanimously condemned the North Korean invasion of South Korea, with UN Security Council Resolution 82. The Soviet Union, a veto-wielding power, had boycotted the Council meetings since January 1950, protesting Taiwan's occupation of China's permanent seat in the UN Security Council.[149] After debating the matter, the Security Council, on 27 June 1950, published Resolution 83 recommending member states provide military assistance to the Republic of Korea. On 27 June, President Truman ordered U.S. air and sea forces to help South Korea. On 4 July, the Soviet Deputy Foreign Minister accused the U.S. of starting armed intervention on behalf of South Korea.[150]

The Soviet Union challenged the legitimacy of the war for several reasons. The ROK intelligence upon which Resolution 83 was based came from U.S. Intelligence; North Korea was not invited as a sitting temporary member of the UN, which violated UN Charter Article 32; and the fighting was beyond the UN Charter's scope, because the initial north–south border fighting was classed as a civil war. Because the Soviet Union was boycotting the Security Council at the time, legal scholars posited that deciding upon an action of this type required the unanimous vote of all the five permanent members including the Soviet Union.[151][152]

Within days of the invasion, masses of ROK soldiers—of dubious loyalty to the Syngman Rhee regime—were retreating southwards or defecting en masse to the northern side, the KPA.[57]

United States' response (July–August 1950)

Man of the Year, the American soldier on Time magazine
cover, 1951

As soon as word of the attack was received,[153] Acheson informed President Truman that the North Koreans had invaded South Korea.[154][155] Truman and Acheson discussed a U.S. invasion response and agreed that the U.S. was obligated to act, comparing the North Korean invasion with Adolf Hitler's aggressions in the 1930s, with the conclusion being that the mistake of appeasement must not be repeated.[156] Several U.S. industries were mobilized to supply materials, labor, capital, production facilities, and other services necessary to support the military objectives of the Korean War.[157] President Truman later explained that he believed fighting the invasion was essential to the U.S. goal of the global containment of communism as outlined in the National Security Council Report 68 (NSC 68) (declassified in 1975):

Communism was acting in Korea, just as Hitler, Mussolini and the Japanese had ten, fifteen, and twenty years earlier. I felt certain that if South Korea was allowed to fall, Communist leaders would be emboldened to override nations closer to our own shores. If the Communists were permitted to force their way into the Republic of Korea without opposition from the free world, no small nation would have the courage to resist threat and aggression by stronger Communist neighbors.[158]

In August 1950, the President and the Secretary of State obtained the consent of Congress to appropriate $12 billion for military action in Korea.[155]

Because of the extensive defense cuts and the emphasis placed on building a nuclear bomber force, none of the services were in a position to make a robust response with conventional military strength. General Omar Bradley, Chairman of the Joint Chiefs of Staff, was faced with reorganizing and deploying a U.S. military force that was a shadow of its World War II counterpart.[159][160]

Acting on Secretary of State Acheson's recommendation, President Truman ordered Supreme Commander for the Allied Powers in Japan General Douglas MacArthur to transfer matériel to the South Korean military while giving air cover to the evacuation of U.S. nationals. The President disagreed with advisers who recommended unilateral U.S. bombing of the North Korean forces and ordered the U.S. Seventh Fleet to protect the Republic of China (Taiwan), whose government asked to fight in Korea. The United States denied Taiwan's request for combat, lest it provoke a PRC retaliation.[161] Because the United States had sent the Seventh Fleet to "neutralize" the Taiwan Strait, Chinese premier Zhou Enlai criticized both the UN and U.S. initiatives as "armed aggression on Chinese territory".[162]

The drive south and Pusan (July–September 1950)

T-34-85 tanks at Masan
tank along the Nakdong River front, August 1950
73rd Heavy Tank Battalion
at the Pusan Docks, Korea.


Task Force Smith, which was a small forward element of the 24th Infantry Division which had been flown in from Japan.[163] On 5 July 1950, Task Force Smith attacked the KPA at Osan but without weapons capable of destroying the KPA tanks. The KPA defeated the U.S. soldiers; the result was 180 American dead, wounded, or taken prisoner. The KPA progressed southwards, pushing back U.S. forces at Pyongtaek, Chonan, and Chochiwon, forcing the 24th Division's retreat to Taejeon, which the KPA captured in the Battle of Taejon; the 24th Division suffered 3,602 dead and wounded and 2,962 captured, including its commander, Major General William F. Dean.[164]

By August, the KPA steadily pushed back the ROK and the Eighth United States Army southwards.[165] The impact of the Truman administration's defense budget cutbacks was now keenly felt, as U.S. troops fought a series of costly rearguard actions. Facing a veteran and well-led KPA force, and lacking sufficient anti-tank weapons, artillery or armor, the Americans retreated and the KPA advanced down the Korean Peninsula.[166][167] During their advance, the KPA purged South Korea's intelligentsia by killing civil servants and intellectuals. On 20 August, General MacArthur warned North Korean leader Kim Il-sung that he would be held responsible for the KPA's atrocities.[168] By September, UN forces were hemmed into a small corner of southeast Korea, near Pusan. This 230-kilometre (140-mile) perimeter enclosed about 10% of Korea, in a line partially defined by the Nakdong River.

Although Kim's early successes led him to predict he would end the war by the end of August, Chinese leaders were more pessimistic. To counter a possible U.S. deployment, Zhou Enlai secured a Soviet commitment to have the Soviet Union support Chinese forces with air cover, and deployed 260,000 soldiers along the Korean border, under the command of Gao Gang. Zhou commanded Chai Chengwen to conduct a topographical survey of Korea, and directed Lei Yingfu, Zhou's military advisor in Korea, to analyze the military situation in Korea. Lei concluded that MacArthur would most likely attempt a landing at Incheon.[169][170] After conferring with Mao that this would be MacArthur's most likely strategy, Zhou briefed Soviet and North Korean advisers of Lei's findings, and issued orders to PLA commanders deployed on the Korean border to prepare for U.S. naval activity in the Korea Strait.[171]

In the resulting

the Naktong Bulge, P'ohang-dong, and Taegu. The United States Air Force (USAF) interrupted KPA logistics with 40 daily ground support sorties, which destroyed 32 bridges, halting most daytime road and rail traffic. KPA forces were forced to hide in tunnels by day and move only at night.[172] To deny military equipment and supplies to the KPA, the USAF destroyed logistics depots, petroleum refineries, and harbors, while the U.S. Navy air forces attacked transport hubs. Consequently, the overextended KPA could not be supplied throughout the south.[173] On 27 August, 67th Fighter Squadron aircraft mistakenly attacked facilities in Chinese territory and the Soviet Union called the UN Security Council's attention to China's complaint about the incident.[174] The U.S. proposed that a commission of India and Sweden determine what the U.S. should pay in compensation, but the Soviets vetoed the U.S. proposal.[175][176]

Meanwhile, U.S. garrisons in Japan continually dispatched soldiers and military supplies to reinforce defenders in the Pusan Perimeter.[177] MacArthur went so far as to call for Japan's rearmament.[178] Tank battalions deployed to Korea directly from the U.S. mainland from the port of San Francisco to the port of Pusan, the largest Korean port. By late August, the Pusan Perimeter had some 500 medium tanks battle-ready.[179] In early September 1950, UN forces outnumbered the KPA 180,000 to 100,000 soldiers.[54][180]

Battle of Incheon (September 1950)

USS Mount McKinley
, 15 September 1950