Korean War The Korean War ( 25 June 1950 – 27 July 1953 ) was a war between the Republic of Korea ( South Korea ) , supported by the United Nations , and the Democratic People ' s Republic of Korea ( North Korea ) , at one time supported by the People ' s Republic of China and the Soviet Union . It was primarily the result of the political division of Korea by an agreement of the victorious Allies at the conclusion of the Pacific War at the end of World War II . The Korean Peninsula was ruled by the Empire of Japan from 1910 until the end of World War II . Following the surrender of the Empire of Japan in September 1945 , American administrators divided the peninsula along the 38th parallel , with U . S . military forces occupying the southern half and Soviet military forces occupying the northern half . The failure to hold free elections throughout the Korean Peninsula in 1948 deepened the division between the two sides ; the North established a communist government , while the South established a right - wing government . The 38th parallel increasingly became a political border between the two Korean states . Although reunification negotiations continued in the months preceding the war , tension intensified . Cross - border skirmishes and raids at the 38th Parallel persisted . The situation escalated into open warfare when North Korean forces invaded South Korea on 25 June 1950 . In 1950 , the Soviet Union boycotted the United Nations Security Council . In the absence of a veto from the Soviet Union , the United States and other countries passed a Security Council resolution authorizing military intervention in Korea . The U . S . provided 88 % of the 341 , 000 international soldiers which aided South Korean forces , with twenty other countries of the United Nations offering assistance . Suffering severe casualties within the first two months , the defenders were pushed back to the Pusan perimeter . A rapid U . N . counter - offensive then drove the North Koreans past the 38th Parallel and almost to the Yalu River , when the People ' s Republic of China ( PRC ) entered the war on the side of North Korea . Chinese intervention forced the Southern - allied forces to retreat behind the 38th Parallel . While not directly committing forces to the conflict , the Soviet Union provided material aid to both the North Korean and Chinese armies . The fighting ended on 27 July 1953 , when the armistice agreement was signed . The agreement restored the border between the Koreas near the 38th Parallel and created the Korean Demilitarized Zone ( DMZ ) , a - wide fortified buffer zone between the two Korean nations . Minor incidents still continue today . From a military science perspective , the Korean War combined strategies and tactics of World War I and World War II : it began with a mobile campaign of swift infantry attacks followed by air bombing raids , but became a static trench war by July 1951 . Names . In the U . S . , the war was initially described by President Harry S . Truman as a " police action " as it was an undeclared military action , conducted under the auspices of the United Nations . It has been referred to in the Anglosphere as " " The Forgotten War " " or " " The Unknown War " " because of the lack of public attention it received both during and after the war , and in relation to the global scale of World War II , which preceded it , and the subsequent angst of the Vietnam War , which succeeded it . In South Korea , the war is usually referred to as " 625 " or the " 6 – 2 – 5 Upheaval " ( " yook - i - o dongnan " ) , reflecting the date of its commencement on 25 June . In North Korea , the war is officially referred to as the " Fatherland Liberation War " ( " Choguk haebang chǒnjaeng " ) or alternatively the " " Chosǒn [ " Korean " ] War " " ( " Chosǒn chǒnjaeng " ) . In China the war is officially called the " War to Resist U . S . Aggression and Aid Korea " ( ) , although the term " " Chaoxian ( Korean ) War " " ( ) is also used in unofficial contexts , along with the term " Korean Conflict " ( ) more commonly used in regions such as Hong Kong and Macau . Background . Imperial Japanese rule ( 1910 – 1945 ) . Upon defeating the Qing Dynasty in the First Sino - Japanese War ( 1894 – 96 ) , the Empire of Japan occupied the Korean Empire — a peninsula strategic to its sphere of influence . A decade later , defeating Imperial Russia in the Russo - Japanese War ( 1904 – 05 ) , Japan made Korea its protectorate with the Eulsa Treaty in 1905 , then annexed it with the Japan – Korea Annexation Treaty in 1910 . Korean nationalists and the intelligentsia fled the country , and some founded the Provisional Korean Government in 1919 , which was headed by Syngman Rhee in Shanghai . This government - in - exile was recognized by few countries . From 1919 to 1925 and beyond , Korean communists led and were the primary agents of internal and external warfare against the Japanese . Korea under Japanese rule was considered to be part of the Empire of Japan as an industrialized colony along with Taiwan , and both were part of the Greater East Asia Co - Prosperity Sphere . In 1937 , the colonial Governor - General , General Jirō Minami , commanded the attempted cultural assimilation of Korea ' s 23 . 5 million people by banning the use and study of Korean language , literature , and culture , to be replaced with that of mandatory use and study of their Japanese counterparts . Starting in 1939 , the populace was required to use Japanese names under the Sōshi - kaimei policy . In 1938 , the Colonial Government established labor conscription . In China , the Nationalist National Revolutionary Army and the Communist People ' s Liberation Army helped organize refugee Korean patriots and independence fighters against the Japanese military , which had also occupied parts of China . The Nationalist - backed Koreans , led by Yi Pom - Sok , fought in the Burma Campaign ( December 1941 – August 1945 ) . The Communists , led by Kim Il - sung among others , fought the Japanese in Korea and Manchuria . During WWII , Japan used Korea ' s food , livestock , and metals for their war effort . Japanese forces in Korea increased from 46 , 000 soldiers in 1941 to 300 , 000 in 1945 . Japanese Korea conscripted 2 . 6 million forced laborers controlled with a collaborationist Korean police force ; some 723 , 000 people were sent to work in the overseas empire and in metropolitan Japan . By 1942 , Korean men were being conscripted into the Imperial Japanese Army . By January 1945 , Koreans comprised 32 % of Japan ' s labor force . In August 1945 , when the U . S . dropped atomic bombs on Hiroshima and Nagasaki , around 25 % of those killed were Koreans . At the end of the war , other world powers did not recognize Japanese rule in Korea and Taiwan . At the Cairo Conference ( November 1943 ) , the Republic of China , the U . K . , and U . S . decided " in due course Korea shall become free and independent " . The Yalta Conference ( February 1945 ) granted to the U . S . S . R . European " buffer zones " — satellite state s accountable to Moscow — as well as an expected Soviet pre - eminence in China and Manchuria , in return for joining the Allied Pacific War effort against Japan . Soviet invasion of Manchuria ( 1945 ) . As agreed with the Allies at the Tehran Conference ( November 1943 ) and the Yalta Conference ( February 1945 ) , the Soviet Union declared war against Japan within three months of the end of the war in Europe , on 9 August 1945 . By 10 August , the Red Army occupied the northern part of the Korean peninsula as agreed , and on 26 August halted at the 38th parallel for three weeks to await the arrival of US forces in the south . On 10 August 1945 , with the Japanese surrender near , the Americans doubted whether the Soviets would honor their part of the Joint Commission , the US - sponsored Korean occupation agreement . A month earlier , Colonel Dean Rusk and Colonel Charles H . Bonesteel III , divided the Korean peninsula at the 38th parallel after hurriedly deciding that the US Korean Zone of Occupation had to have a minimum of two ports . Explaining why the occupation zone demarcation was positioned at the 38th parallel , Rusk observed , " even though it was further north than could be realistically reached by US 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 " , especially when " faced with the scarcity of US 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 . " The Soviets agreed to the US occupation zone demarcation to improve their negotiating position regarding the occupation zones in Eastern Europe , and because each would accept Japanese surrender where they stood . Chinese Civil War ( 1945 – 1949 ) . After the end of the Second Sino - Japanese War , the Chinese Civil War resumed between the Chinese Communists and the Chinese 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 matériel while thousands of Korean 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 in 1949 . As a token of gratitude , between 50 , 000 to 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 . The Chinese support created a deep division between the Korean Communists , and Kim Il - Sung ' s authority within the Communist party was challenged by the Chinese faction led by Pak Il - yu , who was later purged by Kim . After the formation of the People ' s Republic of China in 1949 , the Chinese government named the Western nations , led by the U . S . , as the biggest threat to its national security . Basing this judgment on China ' s century of humiliation beginning in the early 19th century , American support for the Nationalists during the Chinese Civil War , and the ideological struggles between revolutionaries and reactionaries , the Chinese leadership believed that China would become a critical battleground in the United States ' crusade against Communism . As a countermeasure and to elevate China ' s standing among the worldwide Communist movements , the Chinese leadership adopted a foreign policy that actively promoted Communist revolutions throughout territories on China ' s periphery . Korea divided ( 1945 – 1949 ) . At the Potsdam Conference ( July – August 1945 ) , the Allies unilaterally decided to divide Korea — without consulting the Koreans — in contradiction of the Cairo Conference . On 8 September 1945 , U . S . Lt . Gen . John R . Hodge arrived in Incheon to accept the Japanese surrender south of the 38th parallel . Appointed as military governor , General Hodge directly controlled South Korea as head of the United States Army Military Government in Korea ( USAMGIK 1945 – 48 ) . He established control by restoring to power the key Japanese colonial administrators and their Korean police collaborators . The USAMGIK refused to recognise the provisional government of the short - lived People ' s Republic of Korea ( PRK ) because he suspected it was communist . These policies , voiding popular Korean sovereignty , provoked civil insurrections and guerrilla warfare . On 3 September 1945 , Lieutenant General Yoshio Kozuki , Commander , Japanese Seventeenth Area Army , contacted Hodge , telling him that the Soviets were south of the 38th parallel at Kaesong . Hodge trusted the accuracy of the Japanese Army report . In December 1945 , Korea was administered by a U . S . - Soviet Union Joint Commission , as agreed at the Moscow Conference ( 1945 ) . The Koreans were excluded from the talks . The commission decided the country would become independent after a five - year trusteeship action facilitated by each régime sharing its sponsor ' s ideology . The Korean populace revolted ; in the south , some protested , and some rose in arms ; 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 . On 23 September 1946 , an 8 , 000 - strong railroad worker strike began in Pusan . Civil disorder spread throughout the country in what became known as the Autumn uprising . On 1 October 1946 , Korean police killed three students in the Daegu Uprising ; protesters counter - attacked , killing 38 policemen . On 3 October , some 10 , 000 people attacked the Yeongcheon police station , killing three policemen and injuring some 40 more ; elsewhere , some 20 landlords and pro - Japanese South Korean officials were killed . The USAMGIK declared martial law . The right - wing Representative Democratic Council , led by nationalist Syngman Rhee , opposed the Soviet – American trusteeship of Korea , arguing that after 35 years ( 1910 – 45 ) of Japanese colonial rule most Koreans opposed another foreign occupation . The USAMGIK decided to forego the five - year trusteeship agreed upon in Moscow , given the 31 March 1948 United Nations election deadline to achieve an anti - communist civil government in the US Korean Zone of Occupation . On 3 April 1948 , what began as a demonstration commemorating Korean resistance to Japanese rule ended with the Jeju Uprising where between 14 , 000 and 60 , 000 citizens were killed by South Korean soldiers . On 10 May , South Korea convoked its first national general elections that the Soviets first opposed , then boycotted , insisting that the US honor the trusteeship agreed to at the Moscow Conference . North Korea held parliamentary elections three months later on 25 August 1948 . The resultant anti - communist South Korean government promulgated a national political constitution on 17 July 1948 , elected a president , the American - educated strongman Syngman Rhee on 20 July 1948 . The elections were marred by terrorism and sabotage resulting in 600 deaths . The Republic of Korea ( South Korea ) was established on 15 August 1948 . In the Russian Korean Zone of Occupation , the Soviet Union established a Communist North Korean government led by Kim Il - sung . President Rhee ' s régime expelled communists and leftists from southern national politics . Disenfranchised , they headed for the hills , to prepare for guerrilla war against the US - sponsored ROK Government . As nationalists , both Syngman Rhee and Kim Il - Sung were intent upon reunifying Korea under their own political system . The North Koreans gained support from both the Soviet Union and the People ' s Republic of China . They escalated the continual border skirmishes and raids and then prepared to invade . South Korea , with limited matériel , could not match them . During this era , the US government assumed that all communists ( regardless of nationality ) were controlled or directly influenced by Moscow ; thus the U . S . portrayed the civil war in Korea as a Soviet hegemonic maneuver . In October 1948 , South Korean left - wing soldiers rebelled against the government ' s harsh clampdown in April on Jeju island in the Yeosu - Suncheon Rebellion . The Soviet Union withdrew as agreed from Korea in 1948 . U . S . troops withdrew from Korea in 1949 , leaving the South Korean army relatively ill - equipped . On 24 December 1949 , South Korean forces killed 86 to 88 people in the Mungyeong massacre and blamed the crime on communist marauding bands . By early 1950 , Syngman Rhee had about 30 , 000 alleged communists in jails and about 300 , 000 suspected sympathisers enrolled in Bodo League re - education movement . Course of the war . The Korean War begins ( June 1950 ) . In the first half of 1950 , Kim Il - sung travelled to Moscow and Beijing to secure support reunification with the South by force . The Soviet military became extensively involved in North Korea ' s war planning . There are differing accounts of the degree of Soviet support , ranging from support if the North was attacked , to approval , to actually initiating the war . Similarly , some accounts indicate that Chinese support was stronger than Soviet support , and some say it was reluctant . Declassified documents from the Soviet Foreign Ministry and Presidential Archives now show a much clearer , but complex picture of the interactions between Kim , Soviet leader Josef Stalin , and Chinese leader Mao Zedong regarding the decision to invade South Korea . 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 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 . Initially , Stalin did not think the time was right for a war in Korea . Chinese Communist forces still were fighting in China . American forces were still stationed in South Korea ( they would complete their withdrawal in June 1949 ) and Stalin did not want the Soviet Union to become embroiled in a war with the US . But by 1950 , Stalin believed the strategic situation had changed . The Soviets had detonated their first nuclear bomb in September 1949 ; Americans had fully withdrawn from Korea ; the Americans had not intervened to stop the communist victory in China , and Stalin calculated that the Americans would be even less willing to fight in Korea - which had seemingly much less strategic significance . Stalin began a more aggressive strategy in Asia based on these developments , including promising economic and military aid to China through the Sino - Soviet Friendship , Alliance , and Mutual Assistance Treaty . Throughout 1949 and 1950 the Soviets continued to arm North Korea . After the Communist victory in China , ethnic Korean units in the Chinese People ' s Liberation Army ( PLA ) were released to North Korea . The combat experienced veterans from China , the tanks , artillery and aircraft supplied by the Soviets , and rigorous training increased North Korea ' s military superiority over the South , who had been armed by the American military . In April 1950 , Stalin gave Kim permission to invade the South under the condition that Mao would agree to send reinforcements if they became needed . Stalin made it clear that Soviet forces would not directly engage in combat to avoid a war with the Americans . Kim met with Mao in May 1950 . Mao was concerned that the Americans would intervene but agreed to support the North Korean invasion . China desperately needed the economic and military aid promised by the Soviets . At that time , the Chinese were in the process of demobilizing half of the PLA ' s 5 . 6 million soldiers . 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 who had extensive combat experience in WWII were sent to the Soviet Advisory Group in North Korea . These generals completed plans for the attack by May . The original plans were to start with a skirmish 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 South Korean army . The final stage would involve destroying South Korean government remnants , capturing the rest of the 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 part of a planned peace overture that South Korean were certain to reject . On 21 June , Kim Il - Sung requested permission to start with 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 South Korean forces were strengthening their defenses . Stalin agreed to this change of plan . Albeit South Korean and American intelligence officers had in fact predicted an attack , they had incorrectly done so many times before . The Central Intelligence Agency noted the southward movement of North Korean forces , but said it was a " defensive measure " and concluded an invasion was " unlikely " . South Korean and U . S . forces were unprepared . On 23 June , UN observers had inspected the border and failed to notice the imminent attack . The KPA crossed the 38th parallel behind artillery fire at dawn on Sunday 25 June 1950 . The KPA claimed that Republic of Korea Army ( ROK Army ) troops , under command of the régime of the " bandit traitor Syngman Rhee " , had attacked first , and that they would arrest and execute Rhee . There had been frequent skirmishes along the 38th parallel . Fighting began on the strategic Ongjin peninsula in the west . There were initial South Korean claims that they had captured the city of Haeju , and this sequence of events had led some scholars to argue that the South Koreans actually fired first . For South Koreans , the Korean war is sometimes called the " June 25th incident " . Whoever fired the first shots in Ongjin , within an hour , North Korean forces attacked all along the 38th parallel . The North Korean had a combined arms force including tanks supported by heavy artillery . The South Koreans did not have any tanks , anti - tank weapons , nor heavy artillery , that could stop such an attack . In addition , South Koreans deployed their outgunned forces piecemeal and were routed within the first few days . On 27 June , Rhee secretly evacuated from Seoul with government officials . On 28 June , at 2am , the South Korean Army blew up the highway bridge across the Han River in an attempt to stop the North Korean army . The bridge was detonated while 4 , 000 refugees were crossing the bridge , and hundreds were killed . Destroying the bridge also trapped many South Korean military units North of the Han River . In spite of such desperate measures , Seoul fell that same day . A number of South Korean National Assemblymen remained in Seoul when it fell . 48 subsequently pledged allegiance to the North . The South Korean forces , which had 95 , 000 men on 25 June , could account for less than 22 , 000 men by the end of June . In early July , when U . S . forces arrived , South Korean forces were placed under U . S . operational command of the United Nations Command ( Korea ) . There were numerous massacres of civilians and atrocities throughout the Korean war . Both sides began killing civilians even during the first days of the war . On 28 June , Rhee ordered the Bodo League massacre . See also # War crimes . Factors in U . S . intervention . The Truman administration was caught at a crossroads . Before the invasion , Korea was not included in the strategic Asian Defense Perimeter outlined by Secretary of State Acheson . Military strategists were more concerned with the security of Europe against the Soviet Union than East Asia . At the same time , the Administration was worried that a war in Korea could quickly widen into another world war should the Chinese or Soviets decide to get involved as well . One facet of the changing attitude toward Korea and whether to get involved was Japan . Especially after the fall of China to the Communists , " . . . Japan itself increasingly appeared as the major East Asian prize to be protected " . U . S . East Asian experts saw Japan as the critical counterweight to the Soviet Union and China in the region . While there was no United States policy that dealt with South Korea directly as a national interest , its proximity to Japan pushed South Korea to the fore . " 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 US policy toward Japan . " The U . S . was working to shore up Japan which was its protectorate . The other important part of committing to intervention lay in speculation about Soviet action in the event that the U . S . intervene . The Truman administration was fretful that a war in Korea was a diversionary assault that would escalate to a general war in Europe once the U . S . 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 ] " . In Truman ' s mind , this aggression , if left unchecked , would start a chain reaction that would destroy the United Nations and give the go ahead to further Communist aggression elsewhere . Korea was where a stand had to be made ; the difficult part was how . The UN Security Council approved the use of force to help the South Koreans and the U . S . immediately begin using air and naval forces in the area to that end . The Administration still refrained from committing on the ground because some advisors believed the North Koreans could be stopped by air and naval power alone . It was still uncertain if this was a clever ploy by the Soviet Union to catch the U . S . unawares or just a test of U . S . resolve . The decision to commit ground troops and to intervene eventually became viable when a communiqué was received on 27 June from the Soviet Union that alluded it would not move against U . S . forces in Korea . " This opened the way for the sending of American ground forces , for it now seemed less likely that a general war — with Korea as a preliminary diversion — was imminent " . With the Soviet Union ' s tacit agreement that this would not cause an escalation , the U . S . now could intervene with confidence that other commitments would not be jeopardized . United Nations Security Council Resolutions . On 25 June 1950 , the United Nations Security Council unanimously condemned the North Korean invasion of the Republic of Korea , with United Nations Security Council Resolution 82 . The Soviet Union , a veto - wielding power , had boycotted the Council meetings since January 1950 , protesting that the Republic of China ( Taiwan ) , not the People ' s Republic of China , held a permanent seat in the UN Security Council . 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 the South Korean régime . On 4 July the Soviet Deputy Foreign Minister accused the U . S . of starting armed intervention on behalf of South Korea . The Soviet Union challenged the legitimacy of the war for several reasons . The ROK Army 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 Korean conflict was beyond UN Charter scope , because the initial north – south border fighting was classed as a civil war . The Soviet representative boycotted the UN to prevent Security Council action , and to challenge the legitimacy of the UN action ; legal scholars posited that deciding upon an action of this type required the unanimous vote of the five permanent members . Comparison of military forces . 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 , some 150 Yak fighters , 110 attack bombers , 200 artillery pieces , 78 Yak trainers , and 35 reconnaissance aircraft . In addition to the invasion force , the North KPA 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 in - country armies . In contrast , the ROK Army defenders were vastly unprepared , and the political establishment in the south , while well aware of the threat to the north , were unable to convince American administrators of the reality of the threat . In " South to the Naktong , North to the Yalu " ( 1961 ) , R . E . Appleman reports the ROK forces ' low combat readiness as of 25 June 1950 . The ROK Army 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 – piece air force comprising 12 liaison - type and 10 AT6 advanced - trainer airplanes . There were no large foreign military garrisons in Korea at invasion time , but there were large US garrisons and air forces in Japan . Within days of the invasion , masses of ROK Army soldiers — of dubious loyalty to the Syngman Rhee régime — were either retreating southwards or were defecting en masse to the northern side , the KPA . United Nations response ( July – August 1950 ) . Despite the rapid post – Second World War Allied demobilizations , there were substantial U . S . forces occupying Japan ; under General Douglas MacArthur ' s command , they could be made ready to fight the North Koreans . Only the British Commonwealth had comparable forces in the area . On Saturday , 24 June 1950 , U . S . Secretary of State Dean Acheson informed President Truman by telephone , " Mr . President , I have very serious news . The North Koreans have invaded South Korea . " Truman and Acheson discussed a U . S . invasion response with defense department principals , who agreed that the United States was obligated to repel military aggression , paralleling it with Adolf Hitler ' s aggressions in the 1930s , and said that the mistake of appeasement must not be repeated . In his autobiography , President Truman acknowledged that fighting the invasion was essential to the American goal of the global containment of communism as outlined in the National Security Council Report 68 ( NSC - 68 ) ( declassified in 1975 ) : President Truman announced that the U . S . would counter " unprovoked aggression " and " vigorously support the effort of the [ UN ] security council to terminate this serious breach of peace . " In Congress , the Joint Chiefs of Staff Chairman General Omar Bradley warned against appeasement , saying that Korea was the place " for drawing the line " against communist expansion . In August 1950 , the President and the Secretary of State obtained the consent of Congress to appropriate $ 12 billion to pay for the military expenses . Acting on State Secretary Acheson ' s recommendation , President Truman ordered General MacArthur to transfer matériel to the Army of the Republic of Korea 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 US Seventh Fleet to protect the Republic of China ( Taiwan ) , whose government asked to fight in Korea . The U . S . denied ROC ' s request for combat , lest it provoke a communist Chinese retaliation . Because the U . S . 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 . " The Battle of Osan , the first significant American engagement of the Korean War , involved the 540 - soldier Task Force Smith , which was a small forward element of the 24th Infantry Division . On 5 July 1950 , Task Force Smith attacked the North Koreans at Osan but without weapons capable of destroying the North Koreans ' tanks . They were unsuccessful ; the result was 180 dead , wounded , or taken prisoner . The KPA progressed southwards , pushing back the US force 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 the Division ' s Commander , Major General William F . Dean . Overhead , the KPAF shot down 18 USAF fighters and 29 bombers ; the USAF shot down five KPAF fighters . By August , the KPA had pushed back the ROK Army and the Eighth United States Army to the vicinity of Pusan , in southeast Korea . In their southward advance , the KPA purged the Republic of Korea ' s intelligentsia by killing civil servants and intellectuals . On 20 August , General MacArthur warned North Korean leader Kim Il - Sung that he was responsible for the KPA ' s atrocities . By September , the UN Command controlled the Pusan perimeter , enclosing about 10 % of Korea , in a line partially defined by the Nakdong River . Although Kim ' s early successes had led him to predict that he would end the war by the end of August , Chinese leaders were more pessimistic . To counter the possibility of U . S . , 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 . 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 Chinese army commanders deployed on the Korean border to prepare for American naval activity in the Korea Strait . Escalation ( August – September 1950 ) . In the resulting Battle of Pusan Perimeter ( August – September 1950 ) , the U . S . Army withstood KPA attacks meant to capture the city at the Naktong Bulge , P ' ohang - dong , and Taegu . The United States Air Force ( USAF ) interrupted KPA logistics with 40 daily ground support sortie s that 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 . To deny matériel to the KPA , the USAF destroyed logistics depots , petroleum refineries , and harbors , while the U . S . Navy air forces attacked transport hubs . Consequently , the over - extended KPA could not be supplied throughout the south . Meanwhile , U . S . garrisons in Japan continually dispatched soldiers and matériel to reinforce defenders in the Pusan Perimeter . 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 . In early September 1950 , ROK Army and UN Command forces outnumbered the KPA 180 , 000 to 100 , 000 soldiers . The UN forces , once prepared , counterattacked and broke out of the Pusan Perimeter . Battle of Inchon ( September 1950 ) . Against the rested and re - armed Pusan Perimeter defenders and their reinforcements , the KPA were undermanned and poorly supplied ; unlike the UN Command , they lacked naval and air support . To relieve the Pusan Perimeter , General MacArthur recommended an amphibious landing at Inchon ( now known as Incheon ) , well over behind the KPA lines . On 6 July , he ordered Major General Hobart R . Gay , Commander , 1st Cavalry Division , to plan the division ' s amphibious landing at Incheon ; on 12 – 14 July , the 1st Cavalry Division embarked from Yokohama , Japan to reinforce the 24th Infantry Division inside the Pusan Perimeter . Soon after the war began , General MacArthur had begun planning a landing at Incheon , but the Pentagon opposed him . When authorized , he activated a combined U . S . Army and Marine Corps , and ROK Army force . The X Corps , led by General Edward Almond , Commander , consisted of 40 , 000 men of the 1st Marine Division , the 7th Infantry Division and around 8 , 600 ROK Army soldiers . By 15 September attack date , the amphibious assault force faced few KPA defenders at Incheon : military intelligence , psychological warfare , guerrilla reconnaissance , and protracted bombardment facilitated a relatively light battle . However , the bombardment destroyed most of the city of Incheon . After the Incheon landing , the 1st Cavalry Division began its northward advance from the Pusan Perimeter . " Task Force Lynch " ( after Lieutenant Colonel James H . Lynch ) , 3rd Battalion , 7th Cavalry Regiment , and two 70th Tank Battalion units ( Charlie Company and the Intelligence – Reconnaissance Platoon ) effected the " Pusan Perimeter Breakout " through of enemy territory to join the 7th Infantry Division at Osan . The X Corps rapidly defeated the KPA defenders around Seoul , thus threatening to trap the main KPA force in Southern Korea . On 18 September , Stalin dispatched General H . M . Zakharov to Korea to advise Kim Il - sung to halt his offensive around the Pusan perimeter and to redeploy his forces to defend Seoul . Chinese commanders were not briefed on North Korean troop numbers or operational plans . As the overall commander of Chinese forces , Zhou Enlai suggested that the North Koreans should attempt to eliminate the enemy forces at Inchon only if they had reserves of at least 100 , 000 men ; otherwise , he advised the North Koreans to withdraw their forces north . On 25 September , Seoul was recaptured by South Korean forces . American air raids caused heavy damage to the KPA , destroying most of its tanks and much of its artillery . North Korean troops in the south , instead of effectively withdrawing north , rapidly disintegrated , leaving Pyongyang vulnerable . During the general retreat only 25 , 000 to 30 , 000 soldiers managed to rejoin the Northern KPA lines . On 27 September , Stalin convened an emergency session of the Politburo , in which he condemned the incompetence of the KPA command and held Soviet military advisers responsible for the defeat . UN forces cross partition line ( September – October 1950 ) . On 27 September , MacArthur received the top secret National Security Council Memorandum 81 / 1 from Truman reminding him that operations north of the 38th parallel were authorized only if " at the time of such operation there was no entry into North Korea by major Soviet or Chinese Communist forces , no announcements of intended entry , nor a threat to counter our operations militarily . . . " On 29 September MacArthur restored the government of the Republic of Korea under Syngman Rhee . On 30 September , Defense Secretary George Marshall sent an eyes - only message to MacArthur : " We want you to feel unhampered tactically and strategically to proceed north of the 38th parallel . " During October , the ROK police executed people who were suspected to be sympathetic to North Korea , and similar massacres were carried out until early 1951 . On 30 September , Zhou Enlai warned the U . S . that it was prepared to intervene in Korea if the U . S . crossed the 38th parallel . Zhou attempted to advise North Korean commanders on how to conduct a general withdrawal by using the same tactics which had allowed Chinese communist forces to successfully escape Chiang Kai - shek ' s Encirclement Campaigns in the 1930s , but by some accounts North Korean commanders did not utilize these tactics effectively . Bruce Cumings argues , however , the KPA ' s rapid withdrawal was strategic , with troops melting into the mountains from where they could launch guerrilla raids on the UN forces spread out on the coasts . By 1 October 1950 , the UN Command repelled the KPA northwards past the 38th parallel ; the ROK Army crossed after them , into North Korea . MacArthur made a statement demanding the KPA ' s unconditional surrender . Six days later , on 7 October , with UN authorization , the UN Command forces followed the ROK forces northwards . The X Corps landed at Wonsan ( in southeastern North Korea ) and Riwon ( in northeastern North Korea ) , already captured by ROK forces . The Eighth U . S . Army and the ROK Army drove up western Korea and captured Pyongyang city , the North Korean capital , on 19 October 1950 . The 187th Airborne Regimental Combat Team ( " Rakkasans " ) made their first of two combat jumps during the Korean War on 20 October 1950 at Sunchon and Sukchon . The missions of the 187th were to cut the road north going to China , preventing North Korean leaders from escaping from Pyongyang ; and to rescue American prisoners of war . At month ' s end , UN forces held 135 , 000 KPA prisoners of war . Taking advantage of the UN Command ' s strategic momentum against the communists , General MacArthur believed it necessary to extend the Korean War into China to destroy depots supplying the North Korean war effort . President Truman disagreed , and ordered caution at the Sino - Korean border . China intervenes ( October – December 1950 ) . On 27 June 1950 , two days after the KPA invaded and three months before the Chinese entered the war , President Truman dispatched the United States Seventh Fleet to the Taiwan Strait , to prevent hostilities between the Nationalist Republic of China ( Taiwan ) and the People ' s Republic of China ( PRC ) . On 4 August 1950 , with the PRC invasion of Taiwan aborted , Mao Zedong reported to the Politburo that he would intervene in Korea when the People ' s Liberation Army ' s ( PLA ) Taiwan invasion force was reorganized into the PLA North East Frontier Force . China justified its entry into the war as a response to " American aggression in the guise of the UN " . On 20 August 1950 , Premier Zhou Enlai informed the UN that " Korea is China ' s neighbor . . . The Chinese people cannot but be concerned about a solution of the Korean question " . Thus , through neutral - country diplomats , China warned that in safeguarding Chinese national security , they would intervene against the UN Command in Korea . President Truman interpreted the communication as " a bald attempt to blackmail the UN " , and dismissed it . 1 October 1950 , the day that UN troops crossed the 38th parallel , was also the first anniversary of the founding of the People ' s Republic of China . On that day the Soviet ambassador forwarded a telegram from Stalin to Mao and Zhou requesting that China send five to six divisions into Korea , and Kim Il - sung sent frantic appeals to Mao for Chinese military intervention . At the same time , Stalin made it clear that Soviet forces themselves would not directly intervene . In a series of emergency meetings that lasted from 2 – 5 October , Chinese leaders debated whether to send Chinese troops into Korea . There was considerable resistance among many leaders , including senior military leaders , to confronting the U . S . in Korea . Mao strongly supported intervention , and Zhou was one of the few Chinese leaders who firmly supported him . After Lin Biao politely refused Mao ' s offer to command Chinese forces in Korea ( citing his upcoming medical treatment ) , Mao decided that Peng Dehuai would be the commander of the Chinese forces in Korea after Peng agreed to support Mao ' s position . Mao then asked Peng to speak in favor of intervention to the rest of the Chinese leaders . After Peng made the case that if U . S . troops conquered Korea and reached the Yalu they might cross it and invade China the Politburo agreed to intervene in Korea . Later , the Chinese claimed that US bombers had violated PRC national airspace on three separate occasions and attacked Chinese targets before China intervened . On 8 October 1950 , Mao Zedong redesignated the PLA North East Frontier Force as the Chinese People ' s Volunteer Army ( PVA ) . In order to enlist Stalin ' s support , Zhou and a Chinese delegation left for Moscow on 8 October , arrived there on 10 October at which point they flew to Stalin ' s home at the Black Sea . There they conferred with the top Soviet leadership which included Joseph Stalin as well as Vyacheslav Molotov , Lavrentiy Beria and Georgi Malenkov . Stalin initially agreed to send military equipment and ammunition , but warned Zhou that the Soviet Union ' s air force would need two or three months to prepare any operations . In a subsequent meeting , Stalin told Zhou that he would only provide China with equipment on a credit basis , and that the Soviet air force would only operate over Chinese airspace , and only after an undisclosed period of time . Stalin did not agree to send either military equipment or air support until March 1951 . Mao did not find Soviet air support especially useful , as the fighting was going to take place on the south side of the Yalu . Soviet shipments of matériel , when they did arrive , were limited to small quantities of trucks , grenades , machine guns , and the like . Immediately on his return to Beijing on 18 October 1950 , Zhou met with Mao Zedong , Peng Dehuai , and Gao Gang , and the group ordered two hundred thousand Chinese troops to enter North Korea , which they did on 25 October . After consulting with Stalin , on 13 November , Mao appointed Zhou the overall commander and coordinator of the war effort , with Peng as field commander . Orders given by Zhou were delivered in the name of the Central Military Commission . UN aerial reconnaissance had difficulty sighting PVA units in daytime , because their march and bivouac discipline minimized aerial detection . The PVA marched " dark - to - dark " ( 19 : 00 – 03 : 00 ) , and aerial camouflage ( concealing soldiers , pack animals , and equipment ) was deployed by 05 : 30 . Meanwhile , daylight advance parties scouted for the next bivouac site . During daylight activity or marching , soldiers were to remain motionless if an aircraft appeared , until it flew away ; PVA officers were under order to shoot security violators . Such battlefield discipline allowed a three - division army to march the from An - tung , Manchuria to the combat zone in some 19 days . Another division night - marched a circuitous mountain route , averaging daily for 18 days . Meanwhile , on 10 October 1950 , the 89th Tank Battalion was attached to the 1st Cavalry Division , increasing the armor available for the Northern Offensive . On 15 October , after moderate KPA resistance , the 7th Cavalry Regiment and Charlie Company , 70th Tank Battalion captured Namchonjam city . On 17 October , they flanked rightwards , away from the principal road ( to Pyongyang ) , to capture Hwangju . Two days later , the 1st Cavalry Division captured Pyongyang , the North ' s capital city , on 19 October 1950 . On 15 October 1950 , President Truman and General MacArthur met at Wake Island in the mid - Pacific Ocean . This meeting was much publicized because of the General ' s discourteous refusal to meet the President on the continental U . S . To President Truman , MacArthur speculated there was little risk of Chinese intervention in Korea , and that the PRC ' s opportunity for aiding the KPA had lapsed . He believed the PRC had some 300 , 000 soldiers in Manchuria , and some 100 , 000 – 125 , 000 soldiers at the Yalu River . He further concluded that , although half of those forces might cross south , " if the Chinese tried to get down to Pyongyang , there would be the greatest slaughter " without air force protection . After secretly crossing the Yalu River on 19 October , the PVA 13th Army Group launched the First Phase Offensive on 25 October , attacking the advancing U . N . forces near the Sino - Korean border . This military decision made by China solely changed the attitude of the Soviet Union . After 12 days of Chinese troops entering the war , Stalin allowed the Soviet Air Force to provide air cover , and supported more aid to China . After decimating the ROK II Corps at the Battle of Onjong , the first confrontation between Chinese and U . S . military occurred on 1 November 1950 ; deep in North Korea , thousands of soldiers from the PVA 39th Army encircled and attacked the US 8th Cavalry Regiment with three - prong assaults — from the north , northwest , and west — and overran the defensive position flanks in the Battle of Unsan . The surprise assault resulted in the U . N . forces retreating back to the Ch ' ongch ' on River , while the Chinese unexpectedly disappeared into mountain hideouts following victory . It is unclear why the Chinese did not press the attack and follow - up their victory . The UN Command , however , were unconvinced that the Chinese had openly intervened due to the sudden Chinese withdrawal . On 24 November , the Home - by - Christmas Offensive was launched with the U . S . Eighth Army advancing in northwest Korea , while the US X Corps were attacking along the Korean east coast . But the Chinese were waiting in ambush with their Second Phase Offensive . On 25 November at the Korean western front , the PVA 13th Army Group attacked and overran the ROK II Corps at the Battle of the Ch ' ongch ' on River , and then decimated the US 2nd Infantry Division on the UN forces ' right flank . The UN Command retreated ; the U . S . Eighth Army ' s retreat ( the longest in US Army history ) was made possible because of the Turkish Brigade ' s successful , but very costly , rear - guard delaying action near Kunuri that slowed the PVA attack for two days ( 27 – 29 November ) . On 27 November at the Korean eastern front , a US 7th Infantry Division Regimental Combat Team ( 3 , 000 soldiers ) and the U . S . 1st Marine Division ( 12 , 000 – 15 , 000 marines ) were unprepared for the PVA 9th Army Group ' s three - pronged encirclement tactics at the Battle of Chosin Reservoir , but they managed to escape under Air Force and X Corps support fire — albeit with some 15 , 000 collective casualties . By 30 November , the PVA 13th Army Group managed to expel the U . S . Eighth Army from northwest Korea . Retreating from the north faster than they had counter - invaded , the Eighth Army crossed the 38th parallel border in mid December . U . N . morale hit rock bottom when commanding General Walton Walker of the U . S . Eighth Army was killed on 23 December 1950 in an automobile accident . In northeast Korea by 11 December , the U . S . X Corps managed to cripple the PVA 9th Army Group while establishing a defensive perimeter at the port city of Hungnam . The X Corps were forced to evacuate by 24 December in order to reinforce the badly depleted U . S . Eighth Army to the south . During the Hungnam evacuation , about 193 shiploads of U . N . Command forces and matériel ( approximately 105 , 000 soldiers , 98 , 000 civilians , 17 , 500 vehicles , and 350 , 000 tons of supplies ) were evacuated to Pusan . The SS " Meredith Victory " was noted for evacuating 14 , 000 refugees , the largest rescue operation by a single ship , even though it was designed to hold 12 passengers . Before escaping , the U . N . Command forces razed most of Hungnam city , especially the port facilities ; and on 16 December 1950 , President Truman declared a national emergency with Presidential Proclamation No . 2914 , 3 C . F . R . 99 ( 1953 ) , which remained in force until 14 September 1978 . Fighting around the 38th parallel ( January – June 1951 ) . With Lieutenant - General Matthew Ridgway assuming the command of the U . S . Eighth Army on 26 December , the PVA and the KPA launched their Third Phase Offensive ( also known as the " Chinese New Year ' s Offensive " ) on New Year ' s Eve of 1950 . Utilizing night attacks in which U . N . Command fighting positions were encircled and then assaulted by numerically superior troops who had the element of surprise , the attacks were accompanied by loud trumpets and gongs , which fulfilled the double purpose of facilitating tactical communication and mentally disorienting the enemy . UN forces initially had no familiarity with this tactic , and as a result some soldiers panicked , abandoning their weapons and retreating to the south . The Chinese New Year ' s Offensive overwhelmed UN forces , allowing the PVA and KPA to conquer Seoul for the second time on 4 January 1951 . These setbacks prompted General MacArthur to consider using nuclear weapon s against the Chinese or North Korean interiors , with the intention that radioactive fallout zones would interrupt the Chinese supply chains . However , upon the arrival of the charismatic General Ridgway , the " esprit de corps " of the bloodied Eighth Army immediately began to revive . U . N . forces retreated to Suwon in the west , Wonju in the center , and the territory north of Samcheok in the east , where the battlefront stabilized and held . The PVA had outrun its logistics capability and thus were unable to press on beyond Seoul as food , ammunition , and matériel were carried nightly , on foot and bicycle , from the border at the Yalu River to the three battle lines . In late January , upon finding that the PVA had abandoned their battle lines , General Ridgway ordered a reconnaissance - in - force , which became " Operation Roundup " ( 5 February 1951 ) . A full - scale X Corps advance proceeded which fully exploited the UN Command ' s air superiority , concluding with the UN reaching the Han River and recapturing Wonju . After cease fire negotiations failed in January , the United Nations General Assembly passed Resolution 498 on 1 February , condemning PRC as an aggressor , and called upon its forces to withdraw from Korea . In early February , ran the operation to destroy the guerrillas and their sympathizer citizens in Southern Korea . During the operation , the division and police conducted Geochang massacre and Sancheong - Hamyang massacre . In mid - February , the PVA counterattacked with the Fourth Phase Offensive and achieved initial victory at Hoengseong . But the offensive was soon blunted by the IX Corps positions at Chipyong - ni in the center . Units of the U . S . 2nd Infantry Division and the French Battalion fought a short but desperate battle that broke the attack ' s momentum . The battle is sometimes known as the Gettysburg of the Korean War . The battle saw 5 , 600 Korean , American and French defeat a numerically superior Chinese force . Surrounded on all sides , the US 2nd Infantry Division Warrior Division ' s 23rd Regimental Combat Team with an attached French Battalion was hemmed in by more than 25 , 000 Chinese Communist Forces . United Nations Forces had previously retreated in the face of large Communist forces instead of getting cut off , but this time they stood and fought at odds of roughly 15 to 1 . In the last two weeks of February 1951 , " Operation Roundup " was followed by " Operation Killer " , carried out by the revitalized Eighth Army . It was a full - scale , battlefront - length attack staged for maximum exploitation of firepower to kill as many KPA and PVA troops as possible . " Operation Killer " concluded with I Corps re - occupying the territory south of the Han River , and IX Corps capturing Hoengseong . On 7 March 1951 , the Eighth Army attacked with " Operation Ripper " , expelling the PVA and the KPA from Seoul on 14 March 1951 . This was the city ' s fourth conquest in a years ' time , leaving it a ruin ; the 1 . 5 million pre - war population was down to 200 , 000 , and people were suffering from severe food shortages . On 1 March 1951 Mao sent a cable to Stalin , in which he emphasized the difficulties faced by Chinese forces and the urgent need for air cover , especially over supply lines . Apparently impressed by the Chinese war effort , Stalin finally agreed to supply two air force divisions , three anti - aircraft divisions , and six thousand trucks . PVA troops in Korea continued to suffer severe logistical problems throughout the war . In late April Peng Dehuai sent his deputy , Hong Xuezhi , to brief Zhou Enlai in Beijing . What Chinese soldiers feared , Hong said , was not the enemy , but that they had nothing to eat , no bullets to shoot , and no trucks to transport them to the rear when they were wounded . Zhou attempted to respond to the PVA ' s logistical concerns by increasing Chinese production and improving methods of supply , but these efforts were never completely sufficient . At the same time , large - scale air defense training programs were carried out , and the Chinese Air Force began to participate in the war from September 1951 onward . On 11 April 1951 , Commander - in - Chief Truman relieved the controversial General MacArthur , the Supreme Commander in Korea . There were several reasons for the dismissal . MacArthur had crossed the 38th parallel in the mistaken belief that the Chinese would not enter the war , leading to major allied losses . He believed that whether or not to use nuclear weapons should be his own decision , not the President ' s . MacArthur threatened to destroy China unless it surrendered . While MacArthur felt total victory was the only honorable outcome , Truman was more pessimistic about his chances once involved in a land war in Asia , and felt a truce and orderly withdrawal from Korea could be a valid solution . MacArthur was the subject of congressional hearings in May and June 1951 , which determined that he had defied the orders of the President and thus had violated the U . S . Constitution . A popular criticism of MacArthur was that he never spent a night in Korea , and directed the war from the safety of Tokyo . General Ridgway was appointed Supreme Commander , Korea ; he regrouped the UN forces for successful counterattacks , while General James Van Fleet assumed command of the U . S . Eighth Army . Further attacks slowly depleted the PVA and KPA forces ; Operations " Courageous " ( 23 – 28 March 1951 ) and " Tomahawk " ( 23 March 1951 ) were a joint ground and airborne infilltration meant to trap Chinese forces between Kaesong and Seoul . UN forces advanced to " Line Kansas , " north of the 38th parallel . The 187th Airborne Regimental Combat Team ( " Rakkasans " ) second of two combat jumps were on Easter Sunday , 1951 at Munsan - ni , South Korea codenamed Operation Tomahawk . The mission was to get behind Chinese forces and block their movement north . The 60th Indian Parachute Field Ambulance provided the medical cover for the operations , dropping an ADS and a surgical team and treating over 400 battle casualties apart from the civilian casualties that formed the core of their objective as the unit was on a humanitarian mission . The Chinese counterattacked in April 1951 , with the Fifth Phase Offensive ( also known as the " Chinese Spring Offensive " ) with three field armies ( approximately 700 , 000 men ) . The offensive ' s first thrust fell upon I Corps , which fiercely resisted in the Battle of the Imjin River ( 22 – 25 April 1951 ) and the Battle of Kapyong ( 22 – 25 April 1951 ) , blunting the impetus of the offensive , which was halted at the " No - name Line " north of Seoul . On 15 May 1951 , the Chinese commenced the second impulse of the Spring Offensive and attacked the ROK Army and the US X Corps in the east at the Soyang River . After initial success , they were halted by 20 May . At month ' s end , the US Eighth Army counterattacked and regained " Line Kansas , " just north of the 38th parallel . The UN ' s " Line Kansas " halt and subsequent offensive action stand - down began the stalemate that lasted until the armistice of 1953 . Stalemate ( July 1951 – July 1953 ) . For the remainder of the Korean War the UN Command and the PVA fought , but exchanged little territory ; the stalemate held . Large - scale bombing of North Korea continued , and protracted armistice negotiations began 10 July 1951 at Kaesong . On the Chinese side , Zhou Enlai directed peace talks , and Li Kenong and Qiao Guanghua headed the negotiation team . Combat continued while the belligerents negotiated ; the UN Command forces ' goal was to recapture all of South Korea and to avoid losing territory . The PVA and the KPA attempted similar operations , and later effected military and psychological operations in order to test the UN Command ' s resolve to continue the war . The principal battles of the stalemate include the Battle of Bloody Ridge ( 18 August – 15 September 1951 ) , the Battle of the Punchbowl ( 31 August - 21 September 1951 ) , the Battle of Heartbreak Ridge ( 13 September – 15 October 1951 ) , the Battle of Old Baldy ( 26 June – 4 August 1952 ) , the Battle of White Horse ( 6 – 15 October 1952 ) , the Battle of Triangle Hill ( 14 October – 25 November 1952 ) , the Battle of Hill Eerie ( 21 March – 21 June 1952 ) , the sieges of Outpost Harry ( 10 – 18 June 1953 ) , the Battle of the Hook ( 28 – 9 May 1953 ) , the Battle of Pork Chop Hill ( 23 March – 16 July 1953 ) , and the Battle of Kumsong ( 13 – 27 July 1953 ) . Chinese troops suffered from deficient military equipment , serious logistical problems , overextended communication and supply lines , and the constant threat of UN bombers . All of these factors generally led to a rate of Chinese casualties that was far greater than the casualties suffered by UN troops . The situation became so serious that , on November 1951 , Zhou Enlai called a conference in Shenyang to discuss the PVA ' s logistical problems . At the meeting it was decided to accelerate the construction of railways and airfields in the area , to increase the number of trucks available to the army , and to improve air defense by any means possible . These commitments did little to directly address the problems confronting PVA troops . In the months after the Shenyang conference Peng Dehuai went to Beijing several times to brief Mao and Zhou about the heavy casualties suffered by Chinese troops and the increasing difficulty of keeping the front lines supplied with basic necessities . Peng was convinced that the war would be protracted , and that neither side would be able to achieve victory in the foreseeable future . On 24 February 1952 , the Military Commission , presided over by Zhou , discussed the PVA ' s logistical problems with members of various government agencies involved in the war effort . After the government representatives emphasized their inability to meet the demands of the war , Peng , in an angry outburst , shouted : " You have this and that problem . . . You should go to the front and see with your own eyes what food and clothing the soldiers have ! Not to speak of the casualties ! For what are they giving their lives ? We have no aircraft . We have only a few guns . Transports are not protected . More and more soldiers are dying of starvation . Can ' t you overcome some of your difficulties ? " The atmosphere became so tense that Zhou was forced to adjourn the conference . Zhou subsequently called a series of meetings , where it was agreed that the PVA would be divided into three groups , to be dispatched to Korea in shifts ; to accelerate the training of Chinese pilots , to provide more anti - aircraft guns to the front lines ; to purchase more military equipment and ammunition from the Soviet Union ; to provide the army with more food and clothing ; and , to transfer the responsibility of logistics to the central government . Armistice ( July 1953 – November 1954 ) . The on again , off again armistice negotiations continued for two years , first at Kaesong ( southern North Korea ) , then relocated at Panmunjom ( bordering the Koreas ) . A major , problematic negotiation point was prisoner of war ( POW ) repatriation . The PVA , KPA , and UN Command could not agree on a system of repatriation because many PVA and KPA soldiers refused to be repatriated back to the north , which was unacceptable to the Chinese and North Koreans . In the final armistice agreement , signed on 27 July 1953 , a Neutral Nations Repatriation Commission was set up to handle the matter . In 1952 , the US elected a new president , and on 29 November 1952 , the president - elect , Dwight D . Eisenhower , went to Korea to learn what might end the Korean War . With the United Nations ' acceptance of India ' s proposed Korean War armistice , the KPA , the PVA , and the UN Command ceased fire with the battle line approximately at the 38th parallel . Upon agreeing to the armistice , the belligerents established the Korean Demilitarized Zone ( DMZ ) , which has since been patrolled by the KPA and ROKA , US , and Joint UN Commands . The Demilitarized Zone runs northeast of the 38th parallel ; to the south , it travels west . The old Korean capital city of Kaesong , site of the armistice negotiations , originally lay in the pre - war ROK , but now is in the DPRK . The United Nations Command , supported by the United States , the North Korean Korean People ' s Army , and the Chinese People ' s Volunteers , signed the Armistice Agreement on 27 July 1953 to end the fighting . The Armistice also called upon the governments of South Korea , North Korea , China and the United States to participate in continued peace talks . The war is considered to have ended at this point , even though there was no peace treaty . North Korea nevertheless claims that it won the Korean War . After the war , Operation Glory ( July – November 1954 ) was conducted to allow combatant countries to exchange their dead . The remains of 4 , 167 US Army and US Marine Corps dead were exchanged for 13 , 528 KPA and PVA dead , and 546 civilians dead in UN prisoner - of - war camps were delivered to the ROK government . After Operation Glory , 416 Korean War unknown soldiers were buried in the National Memorial Cemetery of the Pacific ( The Punchbowl ) , on the island of Oahu , Hawaii . Defense Prisoner of War / Missing Personnel Office ( DPMO ) records indicate that the PRC and the DPRK transmitted 1 , 394 names , of which 858 were correct . From 4 , 167 containers of returned remains , forensic examination identified 4 , 219 individuals . Of these , 2 , 944 were identified as American , and all but 416 were identified by name . From 1996 to 2006 , the DPRK recovered 220 remains near the Sino - Korean border . Division of Korea ( 1954 – present ) . The Korean Armistice Agreement provided for monitoring by an international commission . Since 1953 , the Neutral Nations Supervisory Commission ( NNSC ) , composed of members from the Swiss and Swedish Armed Forces , has been stationed near the DMZ . In April 1975 , South Vietnam ' s capital was captured by the North Vietnamese army . Encouraged by the success of Communist revolution in Indochina , Kim Il - sung saw it as an opportunity to invade the South . Kim visited China in April of that year , and met with Mao Zedong and Zhou Enlai to ask for military aid . Despite Pyongyang ' s expectations , however , Beijing refused to help North Korea for another war in Korea . Since the armistice , there have been numerous incursions and acts of aggression by North Korea . In 1976 , the axe murder incident was widely publicized . Since 1974 , four incursion tunnels leading to Seoul have been uncovered . In 2010 , a North Korean submarine torpedoed and sank the South Korean corvette ROKS " Cheonan " , resulting in the deaths of 46 sailors . Again in 2010 , North Korea fired artillery shells on Yeonpyeong island , killing two military personnel and two civilians . After a new wave of U . N . sanctions , on 11 March 2013 , North Korea claimed that it had invalidated the 1953 armistice . On 13 March 2013 , North Korea confirmed it ended the 1953 Armistice and declared North Korea " is not restrained by the North - South declaration on non - aggression . " On 30 March 2013 , North Korea stated that it had entered a " state of war " with South Korea and declared that " The long - standing situation of the Korean peninsula being neither at peace nor at war is finally over . " Speaking on 4 April 2013 , United States Secretary of Defense , Chuck Hagel , informed press that Pyongyang had ' formally informed ' the Pentagon that it had ' ratified ' the potential usage of a nuclear weapon against South Korea , Japan and the United States of America , including Guam and Hawaii . Hagel also stated that the US would deploy the Terminal High Altitude Area Defense anti - ballistic missile system to Guam , due to a credible and realistic nuclear threat from North Korea . Characteristics . Casualties . According to the data from the U . S . Department of Defense , the United States suffered 33 , 686 battle deaths , along with 2 , 830 non - battle deaths during the Korean War and 8 , 176 missing in action . South Korea reported some 373 , 599 civilian and 137 , 899 military deaths . Western sources estimate the PVA suffered about 400 , 000 killed and 486 , 000 wounded , while the KPA suffered 215 , 000 killed and 303 , 000 wounded . Data from official Chinese sources , on the other hand , reported that the PVA had suffered 114 , 000 battle deaths , 34 , 000 non - battle deaths , 340 , 000 wounded , 7 , 600 missing and 21 , 400 captured during the war . Among those captured , about 14 , 000 defected to Taiwan while the other 7 , 110 were repatriated to China . Chinese sources also reported that North Korea had suffered 290 , 000 casualties , 90 , 000 captured and a " large " number of civilian deaths . In return , the Chinese and North Koreans estimated that about 390 , 000 soldiers from United States , 660 , 000 soldiers from South Korea and 29 , 000 other UN soldiers were " eliminated " from the battlefield . Recent scholarship has put the full battle death toll on all sides at just over 1 . 2 million . Armored warfare . Initially , North Korean armor dominated the battlefield with Soviet T - 34 - 85 medium tanks designed during the Second World War . The KPA ' s tanks confronted a tankless ROK Army armed with few modern anti - tank weapons , including American World War II – model 2 . 36 - inch ( 60 mm ) M9 bazooka s , effective only against the 45 mm side armor of the T - 34 - 85 tank . The US forces arriving in Korea were equipped with light M24 Chaffee tanks ( on occupation duty in nearby Japan ) that also proved ineffective against the heavier KPA T - 34 tanks . During the initial hours of warfare , some under - equipped ROK Army border units used American 105 mm howitzers as anti - tank gun s to stop the tanks heading the KPA columns , firing high - explosive anti - tank ammunition ( HEAT ) over open sights to good effect ; at the war ' s start , the ROK Army had 91 howitzers , but lost most to the invaders . Countering the initial combat imbalance , the UN Command reinforcement matériel included heavier US M4 Sherman , M26 Pershing , M46 Patton , and British Cromwell and Centurion tanks that proved effective against North Korean armor , ending its battlefield dominance . Unlike in the Second World War ( 1939 – 45 ) , in which the tank proved a decisive weapon , the Korean War featured few large - scale tank battles . The mountainous , heavily forested terrain prevented large masses of tanks from maneuvering . In Korea , tanks served largely as infantry support and mobile artillery pieces . Aerial warfare . The Korean War was the first war in which jet aircraft played a central role . Once - formidable fighters such as the P - 51 Mustang , F4U Corsair , and Hawker Sea Fury — all piston - engined , propeller - driven , and designed during World War II — relinquished their air superiority roles to a new generation of faster , jet - powered fighters arriving in the theater . For the initial months of the war , the P - 80 Shooting Star , F9F Panther , and other jets under the UN flag dominated North Korea ' s prop - driven air force of Soviet Yakovlev Yak - 9 and Lavochkin La - 9 s . The balance would shift with the arrival of the swept wing Soviet MiG - 15 Fagot . The Chinese intervention in late October 1950 bolstered the Korean People ' s Air Force ( KPAF ) of North Korea with the MiG - 15 Fagot , one of the world ' s most advanced jet fighters . The fast , heavily armed MiG outflew first - generation UN jets such as the American F - 80 and Australian and British Gloster Meteors , posing a real threat to B - 29 Superfortress bombers even under fighter escort . Soviet Air Force pilots flew missions for the North to learn the West ' s aerial combat techniques . This direct Soviet participation was a " casus belli " that the UN Command deliberately overlooked , lest the war for the Korean peninsula expand , as the US initially feared , to include three communist countries — North Korea , the Soviet Union , and China — and so escalate to atomic warfare . The USAF moved quickly to counter the MiG - 15 , with three squadrons of its most capable fighter , the F - 86 Sabre , arriving in December 1950 . Although the MiG ' s higher service ceiling — vs . — could be advantageous at the start of a dogfight , in level flight , both swept wing designs attained comparable maximum speeds of around . The MiG climbed faster , but the Sabre turned and dived better . The MiG was armed with one 37 mm and two 23 mm cannons , while the Sabre carried six . 50 caliber ( 12 . 7 mm ) machine guns aimed with radar - ranged gunsights . By early 1951 , the battle lines were established and changed little until 1953 . In summer and autumn 1951 , the outnumbered Sabres of the USAF ' s 4th Fighter Interceptor Wing — only 44 at one point — continued seeking battle in MiG Alley , where the Yalu River marks the Chinese border , against Chinese and North Korean air forces capable of deploying some 500 aircraft . Following Colonel Harrison Thyng ' s communication with the Pentagon , the 51st Fighter - Interceptor Wing finally reinforced the beleaguered 4th Wing in December 1951 ; for the next year - and - a - half stretch of the war , aerial warfare continued . UN forces gained air superiority in the Korean theater after the initial months of the war and maintained it for the duration . This was decisive for the UN : first , for attacking into the peninsular north , and second , for resisting the Chinese intervention . North Korea and China also had jet - powered air forces ; their limited training and experience made it strategically untenable to lose them against the better - trained UN air forces . Thus , the United States and the Soviet Union fed matériel to the war , battling by proxy and finding themselves virtually matched , technologically , when the USAF deployed the F - 86F against the MiG - 15 late in 1952 . Unlike the Vietnam War , in which the Soviet Union only officially sent ' advisers ' , in the Korean aerial war Soviet forces participated via the 64th Airborn Corps . 1106 enemy airplanes were officially downed by the Soviet pilots , 52 of whom earned the title of ' aces ' with more than 5 confirmed kills . Since the Soviet system of confirming air kills erred on the conservative side – the pilot ' s words were never taken into account without corroboration from other witnesses , and enemy airplanes falling into the sea were not counted – the number might exceed 1106 . < ref name = " airwar . ru / history " > < / ref > After the war , and to the present day , the USAF reports an F - 86 Sabre kill ratio in excess of 10 : 1 , with 792 MiG - 15s and 108 other aircraft shot down by Sabres , and 78 Sabres lost to enemy fire . The Soviet Air Force reported some 1 , 100 air - to - air victories and 335 MiG combat losses , while China ' s People ' s Liberation Army Air Force ( PLAAF ) reported 231 combat losses , mostly MiG - 15s , and 168 other aircraft lost . The KPAF reported no data , but the UN Command estimates some 200 KPAF aircraft lost in the war ' s first stage , and 70 additional aircraft after the Chinese intervention . The USAF disputes Soviet and Chinese claims of 650 and 211 downed F - 86s , respectively . However , one unconfirmed source claims that the US Air Force has more recently cited 230 losses out of 674 F - 86s deployed to Korea . The differing tactical roles of the F - 86 and MiG - 15 may have contributed to the disparity in losses : MiG - 15s primarily targeted B - 29 bombers and ground - attack fighter - bombers , while F - 86s targeted the MiGs . The Korean War marked a major milestone not only for fixed - wing aircraft , but also for rotorcraft , featuring the first large - scale deployment of helicopter s for medical evacuation ( medevac ) . In 1944 – 1945 , during the Second World War , the YR - 4 helicopter saw limited ambulance duty , but in Korea , where rough terrain trumped the jeep as a speedy medevac vehicle , helicopters like the Sikorsky H - 19 helped reduce fatal casualties to a dramatic degree when combined with complementary medical innovations such as Mobile Army Surgical Hospital s . The limitations of jet aircraft for close air support highlighted the helicopter ' s potential in the role , leading to development of the AH - 1 Cobra and other helicopter gunships used in the Vietnam War ( 1965 – 75 ) . Bombing North Korea . On 12 August 1950 , the USAF dropped 625 tons of bombs on North Korea ; two weeks later , the daily tonnage increased to some 800 tons . U . S . warplanes dropped more napalm and bombs on North Korea than they did during the whole Pacific campaign of World War II . As a result , almost every substantial building in North Korea was destroyed . The war ' s highest - ranking American POW , US Major General William F . Dean , reported that most of the North Korean cities and villages he saw were either rubble or snow - covered wastelands . US Air Force General Curtis LeMay commented , " we burned down " every " town in North Korea and South Korea , too . " As well as conventional bombing , the Communist side claimed that the US had used biological weapons . Naval warfare . Because neither Korea had a large navy , the Korean War featured few naval battles ; mostly the combatant navies served as naval artillery for their in - country armies . A skirmish between North Korea and the UN Command occurred on 2 July 1950 ; the US Navy cruiser USS " Juneau " , the Royal Navy cruiser HMS " Jamaica " , and the frigate HMS " Black Swan " fought four North Korean torpedo boats and two mortar gunboats , and sank them . During most of the war , the UN navies patrolled the west and east coasts of North Korea and sank supply and ammunition ships to deny the sea to North Korea . Aside from very occasional gunfire from North Korean shore batteries , the main threat to US and UN navy ships was from magnetic mines the North Koreans employed for defensive purposes . During the war , five U . S . Navy ships were lost ( two minesweepers , two minesweeper escorts , and one ocean tug ) all of them to mines , while 87 other warships suffered from slight to moderate damage from North Korean coastal artillery . The USS " Juneau " sank ammunition ships that had been present in her previous battle . The last sea battle of the Korean War occurred at Inchon , days before the Battle of Incheon ; the ROK ship " PC 703 " sank a North Korean mine layer in the Battle of Haeju Island , near Inchon . Three other supply ships were sunk by " PC - 703 " two days later in the Yellow Sea . U . S . threat of atomic warfare . On 5 April 1950 , the Joint Chiefs of Staff ( JCS ) issued orders for the retaliatory atomic bombing of Manchurian PRC military bases , if either their armies crossed into Korea or if PRC or KPA bombers attacked Korea from there . The President ordered the transfer of nine Mark 4 nuclear bomb s " to the Air Force ' s Ninth Bomb Group , the designated carrier of the weapons . . . [ and ] signed an order to use them against Chinese and Korean targets " , which he never transmitted . Many American officials viewed the deployment of nuclear - capable ( but not nuclear - armed ) B - 29 bombers to Britain as helping to resolve the Berlin Blockade of 1948 - 1949 . Truman and Eisenhower both had military experience and viewed nuclear weapons as potentially usable components of their military . During Truman ' s first meeting to discuss the war on 25 June 1950 , he ordered plans be prepared for attacking Soviet forces if they entered the war . By July , Truman approved another B - 29 deployment to Britain , this time with bombs ( but without their cores ) , to remind the Soviets of American offensive ability . Deployment of a similar fleet to Guam was leaked to " The New York Times " . As United Nations forces retreated to Pusan , and the CIA reported that mainland China was building up forces for a possible invasion of Taiwan , the Pentagon believed that Congress and the public would demand using nuclear weapons if the situation in Korea required them . As Chinese forces pushed back the United States forces from the Yalu River , Truman stated during a 30 November 1950 press conference that using nuclear weapons was " always been [ under ] active consideration " , with control under the local military commander . The Indian Ambassador , K . Madhava Panikkar , reports " that Truman announced that he was thinking of using the atom bomb in Korea . But the Chinese seemed totally unmoved by this threat . . . The propaganda against American aggression was stepped up . The ' Aid Korea to resist America ' campaign was made the slogan for increased production , greater national integration , and more rigid control over anti - national activities . One could not help feeling that Truman ' s threat came in very useful to the leaders of the Revolution , to enable them to keep up the tempo of their activities . " After his statement caused concern in Europe , Truman met on 4 December 1950 with UK prime minister and Commonwealth spokesman Clement Attlee , French Premier René Pleven , and Foreign Minister Robert Schuman to discuss their worries about atomic warfare and its likely continental expansion . The US ' s forgoing atomic warfare was not because of " a disinclination by the Soviet Union and People ' s Republic of China to escalate " the Korean War , but because UN allies — notably from the UK , the Commonwealth , and France — were concerned about a geopolitical imbalance rendering NATO defenseless while the US fought China , who then might persuade the Soviet Union to conquer Western Europe . The Joint Chiefs of Staff advised Truman to tell Attlee that the United States would only use nuclear weapons if necessary to protect an evacuation of UN troops , or to prevent a " major military disaster " . On 6 December 1950 , after the Chinese intervention repelled the UN Command armies from northern North Korea , General J . Lawton Collins ( Army Chief of Staff ) , General MacArthur , Admiral C . Turner Joy , General George E . Stratemeyer , and staff officers Major General Doyle Hickey , Major General Charles A . Willoughby , and Major General Edwin K . Wright , met in Tokyo to plan strategy countering the Chinese intervention ; they considered three potential atomic warfare scenarios encompassinging the next weeks and months of warfare . Both the Pentagon and the State Department were nonetheless cautious about using nuclear weapons due to the risk of general war with China and the diplomatic ramifications . Truman and his senior advisors agreed , and never seriously considered using them in early December 1950 despite the poor military situation in Korea . In 1951 , the US escalated closest to atomic warfare in Korea . Because the PRC had deployed new armies to the Sino - Korean frontier , pit crews at the Kadena Air Base , Okinawa , assembled atomic bombs for Korean warfare , " lacking only the essential pit nuclear cores . " In October 1951 , the US effected Operation Hudson Harbor to establish nuclear weapons capability . USAF B - 29 bombers practised individual bombing runs from Okinawa to North Korea ( using dummy nuclear or conventional bombs ) , coordinated from Yokota Air Base in east - central Japan . " Hudson Harbor " tested " actual functioning of all activities which would be involved in an atomic strike , including weapons assembly and testing , leading , ground control of bomb aiming " . The bombing run data indicated that atomic bombs would be tactically ineffective against massed infantry , because the " timely identification of large masses of enemy troops was extremely rare . " Ridgway was authorized to use nuclear weapons if a major air attack originated from outside Korea . An envoy was sent to Hong Kong to deliver a warning to China . The message likely caused Chinese leaders to be more cautious about potential American use of nuclear weapons , but whether they learned about the B - 29 deployment is unclear and the failure of the two major Chinese offensives that month likely was what caused them to shift to a defensive strategy in Korea . The B - 29s returned to the United States in June . When Eisenhower succeeded Truman in early 1953 he was similarly cautious about using nuclear weapons in Korea , including for diplomatic purposes to encourage progress in the ongoing truce discussions . The administration prepared contingency plans for using them against China , but like Truman , the new president feared that doing so would result in Soviet attacks on Japan . The war ended as it had begun , without American nuclear weapons deployed near battle . War crimes . Civilian deaths and massacres . There were numerous atrocities and massacres of civilians throughout the Korean war committed by both the North and South Koreans . Many of them started on the first days of the war . South Korean President Syngman Rhee ordered the Bodo League massacre on 28 June , beginning numerous killings of more than 100 , 000 suspected leftist sympathizers and their families by South Korean officials and right - wing groups . During the massacre , the British protested to their allies and saved some citizens . In occupied areas , North Korean Army political officers purged South Korean society of its intelligentsia by executing every educated person — academic , governmental , religious — who might lead resistance against the North ; the purges continued during the NPA retreat . R . J . Rummel estimated that the North Korean Army executed at least 500 , 000 civilians during the Korean War with many dying in North Korea ' s drive to conscript South Koreans to their war effort . When the North Koreans retreated north in September 1950 , they abducted tens of thousands of South Korean men . The reasons are not clear but many of the victims had skills , or had been arrested as right - wing activists . In addition to conventional military operations , North Korean soldiers fought the U . N . forces by infiltrating guerrillas among refugees . These soldiers disguised as refugees would approach UN forces asking for food and help , then open fire and attack . U . S . troops acted under a " shoot - first - ask - questions - later " policy against any civilian refugee approaching U . S . battlefield positions , a policy that led U . S . soldiers to kill an estimated 400 civilians at No Gun Ri ( 26 – 29 July 1950 ) in central Korea because they believed some of the refugees killed to be North Korean soldiers in disguise . The South Korean Truth and Reconciliation Commission defended this policy as a " military necessity " . Beginning in 2005 , the South Korean Truth and Reconciliation Commission has investigated numerous atrocities committed by the Japanese colonial government and the authoritarian South Korean governments that followed it . It has investigated atrocities before , during and after the Korean War . Some of the worst pre - Korean War violence involved the Jeju Uprising ( 1948 – 49 ) . The Commission has verified over 14 , 000 civilians were killed in the brutal fighting between South Korean military and paramilitary units against pro - North Korean guerrillas . Although most of the fighting had subsided by 1949 , fighting continued until 1950 . The Commission estimates 86 % of the civilians were killed by South Korean forces . The Americans on the island documented the events , but never intervened . Recently declassified US documents show that the South Koreans massacred entire families of leftists near Daejeon . Many of the victims were members of the Bodo League . The Truth and Reconciliation Commission estimates that at least 100 , 000 people — and possibly more — were executed in the summer of 1950 . The victims include political prisoners , civilians who were killed by US forces , civilians who allegedly collaborated with communist North Korea or local communist groups , and civilians killed by communist insurgents . The Commission has found evidence that both the South Korean government and the leftists murdered the children of their enemies . Prisoners of war . During the first days of the war North Korean soldiers committed the Seoul National University Hospital Massacre . The US reported that North Korea mistreated prisoners of war : soldiers were beaten , starved , put to forced labor , marched to death , and summarily executed . The KPA killed POWs at the battles for Hill 312 , Hill 303 , the Pusan Perimeter , and Daejeon — discovered during early after - battle mop - up actions by the UN forces . Later , a US Congress war crime s investigation , the " United States Senate Subcommittee on Korean War Atrocities of the Permanent Subcommittee of the Investigations of the Committee on Government Operations " reported that " . . . two - thirds of all American prisoners of war in Korea died as a result of war crimes " . Although the Chinese rarely executed prisoners like their Korean counterparts , mass starvation and diseases swept through the Chinese - run POW camps during the winter of 1950 – 51 . About 43 percent of all US POWs died during this period . The Chinese defended their actions by stating that all Chinese soldiers during this period were suffering mass starvation and diseases due to logistical difficulties . The UN POWs pointed out that most of the Chinese camps were located near the easily supplied Sino - Korean border , and that the Chinese withheld food to force the prisoners to accept the communism indoctrination programs . North Korea may have detained up to 50 , 000 South Korean POWs after the ceasefire . Over 88 , 000 South Korean soldiers were missing and the Communists ' themselves had claimed they had captured 70 , 000 South Koreans . However , when ceasefire negotiations began in 1951 , the Communists reported they held only 8 , 000 South Koreans . The UN Command protested the discrepancies and alleged the Communists were forcing South Korean POWs to join the KPA . The Communists denied such allegations . They claimed their POW rosters were small because many POWs were killed in UN air raids and they had released ROK soldiers at the front . They insisted that only volunteers were allowed to serve in the KPA . By early 1952 , UN negotiators gave up trying to get back the missing South Koreans . The POW exchange proceeded without access to South Korean POWs not on the Communist rosters . North Korea continued to claim that any South Korean POW who stayed in the North did so voluntarily . However , since 1994 , South Korean POWs have been escaping North Korea on their own after decades of captivity . As of 2010 , the South Korean Ministry of Unification reports that 79 ROK POWs have escaped the North as of 2010 . The South Korean government estimates 500 South Korean POWs continue to be detained in North Korea . The escaped POWs have testified about their treatment and written memoirs about their lives in North Korea . They report that they were not told about the POW exchange procedures , and were assigned to work in mines in the remote northeastern regions near the Chinese and Russian border . Declassified Soviet Foreign Ministry documents corroborate such testimony . In 1997 the Geoje POW Camp in South Korea was turned into a memorial . Starvation . In December 1950 , National Defense Corps was founded , the soldiers were 406 , 000 drafted citizens . In the winter of 1951 , 50 , 000 to 90 , 000 South Korean National Defense Corps soldiers starved to death while marching southward under the Chinese offensive when their commanding officers embezzled funds earmarked for their food . This event is called the National Defense Corps Incident . There is no evidence that Syngman Rhee was personally involved in or benefited from the corruption . Recreations . In 1950 , Secretary of Defence George C . Marshall and Secretary of the Navy Francis P . Matthews called on the USO which was disbanded by 1947 to provide support for U . S servicepersons . By the end of the war , more than 113 , 000 American USO volunteers were working at home front and abroad . Many stars came to Korea to give their performances . Throughout the Korean War , U . N . Comfort Station s were operated by South Korean officials for U . N soldiers . Aftermath . Mao Zedong ' s decision to confront the United States in the Korean War was a direct attempt to confront what the Communist bloc viewed as the most powerful anti - Communist power in the world , undertaken at a time when the Chinese Communist regime was still consolidating its own power after winning the Chinese Civil War . Mao primarily supported intervention not to save North Korea or to appease the Soviet Union , but because he believed that a military conflict with the United States was inevitable after United States entered the Korean War . Mao ' s secondary motive was to improve his own prestige inside the communist international community by demonstrating that his Marxist concerns were international . In his later years Mao believed that Stalin only gained a positive opinion of him after China ' s entrance into the Korean War . Inside Mainland China , the war improved the long - term prestige of Mao , Zhou , and Peng , allowing the Chinese Communist Party to increase its legitimacy while weakening anti - Communist dissent . China emerged from the Korean War united by a sense of national pride , despite the war ' s enormous costs . The Chinese people have the point of view of the war being initiated by the United States and South Korea . In Chinese media , the Chinese war effort is considered as an example of China ' s engaging the strongest power in the world with an under - equipped army , forcing it to retreat , and fighting it to a military stalemate . These successes were contrasted with China ' s historical humiliations by Japan and by Western powers over the previous hundred years , highlighting the abilities of the PLA and the . The most significant negative long - term consequence of the war ( for China ) was that it led the United States to guarantee the safety of Chiang Kai - shek ' s regime in Taiwan , effectively ensuring that Taiwan would remain outside of PRC control until the present day . Mao had also discovered the usefulness of large - scale mass movement s in the war while implementing it among most of his ruling measures over PRC . Finally , anti - American sentiments , which were already a significant factor during the Chinese Civil War , was ingrained into Chinese culture during the Communist propaganda campaigns of the Korean War . The Korean War affected other participant combatants . Turkey , for example , entered NATO in 1952 and the foundation for bilateral diplomatic and trade relations was laid . Racial integration efforts in the U . S . military began during the Korean War , where African Americans fought in integrated units for the first time . Among the 1 . 8 million American soldiers who fought in the Korean War there were more than 100 , 000 African Americans . Post - war recovery was different in the two Koreas . South Korea stagnated in the first post - war decade . In 1953 , South Korea and the United States concluded a Mutual Defense Treaty . In 1960 , April Revolution occurred students joined anti - Syngman Rhee demonstration , 142 were killed by police , in consequence Syngman Rhee resigned and defected to the United States . Park Chung - hee ' s May 16 coup enabled social stability . In 1960s , western princess earned 25 percent of South Korean GNP with the help of their military government . During 1965 - 1973 , South Korea dispatched troops to Vietnam , got 235 , 560 , 000 dollars allowance and military procurement from US . GNP increased fivefold during the Vietnam War . South Korea industrialized and modernized . Contemporary North Korea remains underdeveloped , but its external debt is 30 times lower than that of South Korea . South Korea had one of the world ' s fastest growing economies from the early 1960s to the late 1990s . In 1957 South Korea had a lower per capita GDP than Ghana , and by 2010 it was ranked thirteenth in the world ( Ghana was 86th ) . Post - war , about 100 , 000 North Koreans were executed in purges . According to Rummel , forced labor and concentration camps were responsible for over one million deaths in North Korea from 1945 to 1987 ; others have estimated 400 , 000 deaths in concentration camps alone . Estimates based on the most recent North Korean census suggest that 240 , 000 to 420 , 000 people died as a result of the 1990s North Korean famine and that there were 600 , 000 to 850 , 000 unnatural deaths in North Korea from 1993 to 2008 . The North Korean government has been accused of " crimes against humanity " for its alleged culpability in creating and prolonging the 1990s famine . A study by South Korean anthropologists of North Korean children who had defected to China found that 18 - year - old males were 5 inches shorter than South Koreans their age due to malnutrition . Korean anti - Americanism after the war was fueled by the presence and behavior of American military personnel ( USFK ) and U . S . support for the authoritarian regime , a fact still evident during the country ' s democratic transition in the 1980s . However , anti - Americanism has declined significantly in South Korea in recent years , from 46 % favorable in 2003 to 74 % favorable in 2011 , making South Korea one of the most pro - American countries in the world . In addition a large number of mixed race ' G . I . babies ' ( offspring of U . S . and other U . N . soldiers and Korean women ) were filling up the country ' s orphanages . Korean traditional society places significant weight on paternal family ties , bloodlines , and purity of race . Children of mixed race or those without fathers are not easily accepted in South Korean society . International adoption of Korean children began in 1954 . The U . S . Immigration Act of 1952 legalized the naturalization of non - whites as American citizens , and made possible the entry of military spouses and children from South Korea after the Korean War . With the passage of the Immigration Act of 1965 , which substantially changed U . S . immigration policy toward non - Europeans , Koreans became one of the fastest growing Asian groups in the United States .