Editing Korean War (section)

==Background==
===Imperial Japanese rule (1910–1945)===
{{Main|Korea under Japanese rule}}
The [[Empire of Japan]] diminished the influence of [[Qing dynasty|China]] over Korea in the [[First Sino-Japanese War]] (1894–95).{{Sfn|Stokesbury|1990|p=}} A decade later, after defeating [[Russian Empire|Imperial Russia]] in the [[Russo-Japanese War]], Japan made the Korean Empire its [[protectorate]] with the [[Eulsa Treaty]] in 1905, then annexed it with the [[Japan–Korea Treaty of 1910]].<ref name="Schnabel1972"/>

Many [[Korean nationalism|Korean nationalists]] fled the country. The [[Provisional Government of the Republic of Korea]] was founded in 1919 in [[Republic of China (1912–1949)|Nationalist China]]. It failed to achieve international recognition, failed to unite the nationalist groups, and had a fractious relationship with its US-based founding president, [[Syngman Rhee]].{{Sfn|Stueck|2002|pp=19–20}}

In China, the nationalist [[National Revolutionary Army]] and the communist [[People's Liberation Army]] (PLA) helped organize Korean refugees against the Japanese military, which had also occupied parts of China. The Nationalist-backed Koreans, led by [[Lee Beom-seok (prime minister)|Yi Pom-Sok]], fought in the [[Burma campaign]] (1941–45). The communists, led by, among others, [[Kim Il Sung]], fought the Japanese in Korea and [[Manchuria]].{{Sfn|Cumings|2005|pp=160–61, 195–96}} At the [[Cairo Conference]] in 1943, China, the UK, and the US decided that "in due course, Korea shall become free and independent".<ref name="Early1943"/>

===Korea divided (1945–1949)===
{{Main|Division of Korea}}

At the [[Tehran Conference]] in 1943 and the [[Yalta Conference]] in February 1945, the Soviet Union promised to join its [[Allies of World War II|allies]] in the [[Pacific War]] within three months of the [[Victory in Europe Day|victory in Europe]]. [[Soviet–Japanese War|The USSR declared war on Japan]] and [[Soviet invasion of Manchuria|invaded Manchuria]] on 8 August 1945.{{Sfn|Dear|Foot|1995|p=516}}<ref name="Whelan1991"/> On 10 August, Soviet forces entered northern Korea and secured most major cities in the north by 24 August.<ref name=":02">{{Cite book |last=Li |first=Xiaobing |title=The Cold War in East Asia |date=2018 |publisher=[[Routledge]] |isbn=978-1-138-65179-1 |location=Abingdon, Oxon}}</ref>{{Rp|page=82}} Japanese resistance was light.<ref name=":02" />{{Rp|page=82}} Having fought Japan on Korean soil, the Soviet forces were well-received by Koreans.<ref name=":02" />{{Rp|page=82}}

On 10 August in [[Washington, D.C.|Washington]], US Colonels [[Dean Rusk]] and [[Charles H. Bonesteel III]] were assigned to divide Korea into Soviet and US occupation zones and proposed the [[38th parallel north|38th parallel]] as the dividing line. This was incorporated into the US [[General Order No. 1]], which responded to the [[Surrender of Japan|Japanese surrender]] on 15 August. Explaining the choice of the 38th parallel, Rusk observed, "Even though it was further north than could be realistically reached by U. S. [''sic''] forces in the event of Soviet disagreement&nbsp;... we felt it important to include the capital of Korea in the area of responsibility of American troops".{{Sfn|Goulden|1983|p=17}}<ref>{{Cite web |title=Foreign Relations of the United States: Diplomatic Papers, 1945, The British Commonwealth, The Far East, Volume VI - Office of the Historian |url=https://history.state.gov/historicaldocuments/frus1945v06/d771 |access-date=2023-01-05 |website=history.state.gov |archive-date=5 January 2023 |archive-url=https://web.archive.org/web/20230105150706/https://history.state.gov/historicaldocuments/frus1945v06/d771 |url-status=live }}</ref> [[Joseph Stalin]], however, maintained his wartime policy of cooperation, and on 16 August, the Red Army halted at the 38th parallel for three weeks to await the arrival of US forces.{{Sfn|Stokesbury|1990|pp=24, 25}}

On 7 September 1945, General [[Douglas MacArthur]] issued Proclamation No. 1 to the people of Korea, announcing US military control over Korea south of the 38th parallel and establishing English as the official language during military control.<ref>{{Cite web |title=Foreign Relations of the United States: Diplomatic Papers, 1945, The British Commonwealth, The Far East, Volume VI - Office of the Historian |url=https://history.state.gov/historicaldocuments/frus1945v06/d776 |access-date=2022-06-23 |website=history.state.gov |archive-date=11 November 2021 |archive-url=https://web.archive.org/web/20211111012102/https://history.state.gov/historicaldocuments/frus1945v06/d776 |url-status=live }}</ref> On 8 September, US Lieutenant General [[John R. Hodge]] arrived in [[Incheon]] to accept the Japanese surrender south of the 38th parallel.{{Sfn|Appleman|1998|p=}} Appointed as military governor, Hodge directly controlled South Korea as head of the [[United States Army Military Government in Korea]] (USAMGIK 1945–48).{{Sfn|Halberstam|2007|p=63}}

In December 1945, Korea was administered by a [[Division of Korea#US–Soviet Joint Commission|US–Soviet Union Joint Commission]], as agreed at the [[Moscow Conference (1945)|Moscow Conference]], to grant independence after a five-year trusteeship.{{Sfn|Stokesbury|1990|pp=25–26}}{{Sfn|Becker|2005|p=53}} Waiting five years for independence was unpopular among Koreans, and riots broke out.<ref name="Schnabel1972" /> The Communist Party supported the trusteeship, while [[Kim Ku]] and [[Syngman Rhee]] led the anti-trusteeship movement against both the [[United States Army Military Government in Korea|U.S. military government]] and the [[Soviet Civil Administration|Soviet military administration]].<ref>{{citation |last1=Yoon |first1=Sang-hyun |title=anti- trusteeship movement|date=2011 |publisher=([[Encyclopedia of Korean Culture]], 한국민족문화대백과)|url=https://encykorea.aks.ac.kr/Article/E0033478}}</ref><ref>{{citation |last1=Park |first1=Myung-soo |title=The Second Anti-trusteeship Campaign and Korean Political Landscapes in Early 1947 |journal=Kci |date=2017 |volume=74 |pages=65–93 |publisher=[[Korea Citation Index]] |url=https://www.kci.go.kr/kciportal/ci/sereArticleSearch/ciSereArtiView.kci?sereArticleSearchBean.artiId=ART002297403}}</ref> To contain them, the USAMGIK banned strikes on 8 December and outlawed the [[People's Republic of Korea|PRK Revolutionary Government]] and People's Committees on 12 December.{{Sfn|Jager|2013|pp=41–42}} Following further civilian unrest,{{Sfn|Cumings|1981|loc=chapter 3, 4}} the USAMGIK declared [[martial law]].

Citing the inability of the Joint Commission to make progress, the UN decided to hold an election under UN auspices to create an independent Korea, as stated in UN General Assembly Resolution 112. The Soviet authorities and Korean communists refused to participate in the election. The final attempt to establish a unified government was thwarted by North Korea's refusal. Due to concerns about division caused by an election without North Korea's participation, many South Korean politicians boycotted it.{{Sfn|Cumings|2005|p=211}}{{Sfn|Jager|2013|p=47}} The [[1948 South Korean general election]] was held in May.{{Sfn|Stokesbury|1990|p=26}}<ref name="Time1946" /> The resultant South Korean government promulgated a national political constitution on 17 July and elected Syngman Rhee as [[President of South Korea|president]] on 20 July. The Republic of Korea (South Korea) was established on 15 August 1948.

In the Soviet-Korean Zone of Occupation, the Soviets agreed to the establishment of a communist government{{Sfn|Stokesbury|1990|p=26}} led by Kim Il Sung.<ref name="AMH" /> The [[1948 North Korean parliamentary election]]s took place in August.{{Sfn|Malkasian|2001|p=13}} The Soviet Union withdrew its forces in 1948 and the US in 1949.<ref>{{Cite encyclopedia |title=Korea - Division of Korea |encyclopedia=Encyclopedia Britannica |url=https://www.britannica.com/place/Korea/Division-of-Korea |access-date=24 June 2022 |archive-date=27 February 2022 |archive-url=https://web.archive.org/web/20220227041057/https://www.britannica.com/place/Korea/Division-of-Korea |url-status=live }}</ref><ref>{{Cite web |title=Statement by the President on the Decision To Withdraw U.S. Forces From Korea, 1947-1949. {{!}} The American Presidency Project |url=https://www.presidency.ucsb.edu/documents/statement-the-president-the-decision-withdraw-us-forces-from-korea-1947-1949 |access-date=24 June 2022 |website=presidency.ucsb.edu |archive-date=18 August 2022 |archive-url=https://web.archive.org/web/20220818010130/https://www.presidency.ucsb.edu/documents/statement-the-president-the-decision-withdraw-us-forces-from-korea-1947-1949 |url-status=live }}</ref>

===Chinese Civil War (1945–1949)===
With the end of the [[Second Sino-Japanese War|war with Japan]], the [[Chinese Civil War]] resumed in earnest between the [[Chinese Communist Party|Communists]] and the [[Kuomintang|Nationalist]]-led government. While the Communists were struggling for supremacy in Manchuria, they were supported by the North Korean government with [[materiel|matériel]] and manpower.{{Sfn|Chen|1994|p=110}} According to Chinese sources, the North Koreans donated 2,000 railway cars worth of supplies while thousands of Koreans served in the Chinese PLA during the war.{{Sfn|Chen|1994|pp=110–11}} North Korea also provided the Chinese Communists in Manchuria with a safe refuge for non-combatants and communications with the rest of China.{{Sfn|Chen|1994|p=110}} As a token of gratitude, between 50,000 and 70,000 Korean veterans who 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.{{Sfn|Chen|1994|p=110}} China promised to support the North Koreans in the event of a war against South Korea.{{Sfn|Chen|1994|p=111}}

===Communist insurgency in South Korea (1948–1950)===
{{More citations needed section|date=November 2024}}
By 1948, a North Korea-backed insurgency had broken out in the southern half of the peninsula.{{citation needed|date=May 2025}} This was exacerbated by the undeclared border war between the Koreas, which saw division-level engagements and thousands of deaths on both sides.<ref>Gibby, Bryan (2012). ''Will to Win: American Military Advisors in Korea, 1946–1953''. University Alabama Press. p. 72.</ref> The ROK was almost entirely trained and focused on counterinsurgency, rather than conventional warfare. They were equipped and advised by a force of a few hundred American officers, who were successful in helping the ROKA to subdue guerrillas and hold its own against [[Korean People's Army|North Korean military]] (Korean People's Army, KPA) forces along the 38th parallel.<ref name="Bryan, p. 76">Bryan, p. 76.</ref> Approximately 8,000 South Korean soldiers and police officers died in the insurgent war and border clashes.<ref name="EB">{{Cite web |title=Korean War &#124; Combatants, Summary, Years, Map, Casualties, & Facts |url=https://www.britannica.com/event/Korean-War |website=Encyclopedia Britannica |date=29 May 2023 |access-date=25 July 2019 |archive-date=24 April 2016 |archive-url=https://web.archive.org/web/20160424090911/https://www.britannica.com/event/Korean-War |url-status=live }}</ref>

The [[Jeju uprising|first socialist uprising]] occurred without direct North Korean participation, though the guerrillas still professed support for the northern government. Beginning in April 1948 on [[Jeju Island]], the campaign saw arrests and repression by the South Korean government in the fight against the South Korean Labor Party, resulting in 30,000 violent deaths, among them 14,373 civilians, of whom ~2,000 were killed by rebels and ~12,000 by ROK security forces. The [[Yeosu–Suncheon rebellion]] overlapped with it, as several thousand army defectors waving red flags massacred right-leaning families. This resulted in another brutal suppression by the government and between 2,976 and 3,392 deaths. By May 1948, both uprisings had been crushed.<ref>{{Citation |last=박 |first=동찬 |title=여수·순천 10·19사건 (麗水·順天 10·19事件) |encyclopedia=한국민족문화대백과사전 [Encyclopedia of Korean Culture] |trans-title=Yeosu-Suncheon 10.19 rebellion |url=https://encykorea.aks.ac.kr/Article/E0036410 |access-date=2025-03-28 |publisher=Academy of Korean Studies |language=ko}}</ref>

Insurgency reignited in the spring of 1949 when attacks by guerrillas in the mountainous regions (buttressed by army defectors and North Korean agents) increased.{{citation needed|date=September 2024}} Insurgent activity peaked in late 1949 as the ROKA engaged so-called People's Guerrilla Units. Organized and armed by the North Korean government, and backed by 2,400 KPA commandos who had infiltrated through the border, these guerrillas launched an offensive in September aimed at undermining the South Korean government and preparing the country for the KPA's arrival in force. This offensive failed.<ref>Bryan, pp. 76-77.</ref>{{additional citation needed|date=September 2024}} However, the guerrillas were now entrenched in the Taebaek-san region of the [[North Gyeongsang Province]] and the border areas of the [[Gangwon Province, South Korea|Gangwon Province]].<ref name="Bryan, p. 78">Bryan, p. 78.</ref>

While the insurgency was ongoing, the ROKA and KPA engaged in battalion-sized battles along the border, starting in May 1949.<ref name="Bryan, p. 76"/> Border clashes between South and North continued on 4 August 1949, when thousands of North Korean troops attacked South Korean troops occupying territory north of the 38th parallel. The 2nd and 18th ROK Infantry Regiments repulsed attacks in Kuksa-bong,<ref>{{Cite web |title=Kuksa-bong |url=https://mapcarta.com/16197292 |access-date=11 November 2017 |website=Mapcarta |archive-date=21 October 2017 |archive-url=https://web.archive.org/web/20171021061118/https://mapcarta.com/16197292 |url-status=live }}</ref> and KPA troops were "completely routed".<ref>{{Cite book |last=Cumings |first=Bruce |url=https://books.google.com/books?id=lY5-7ZirsmgC&q=august+4+1949 |title=The Korean War: A History |date=27 July 2010 |publisher=Random House Publishing Group |isbn=9780679603788 |access-date=11 November 2017 |via=Google Books}}</ref> Border incidents decreased by the start of 1950.<ref name="Bryan, p. 78"/>

Meanwhile, counterinsurgencies in the South Korean interior intensified; persistent operations, paired with worsening weather, denied the guerrillas sanctuary and wore away their fighting strength. North Korea responded by sending more troops to link up with insurgents and build more partisan cadres; North Korean infiltrators had reached 3,000 soldiers in 12 units by the start of 1950, but all were destroyed or scattered by the ROKA.<ref>Bryan, pp. 79-80.</ref>

On 1 October 1949, the ROKA launched a three-pronged assault on the insurgents in [[South Jeolla Province|South Cholla]] and [[Daegu|Taegu]]. By March 1950, the ROKA claimed 5,621 guerrillas killed or captured and 1,066 small arms seized. This operation crippled the insurgency. Soon after, North Korea made final attempts to keep the uprising active, sending battalion-sized units of infiltrators under the commands of Kim Sang-ho and Kim Moo-hyon. The first battalion was reduced to a single man over the course of engagements by the ROKA [[8th Maneuver Division|8th Division]]. The second was annihilated by a two-battalion [[Hammer and anvil|hammer-and-anvil maneuver]] by units of the ROKA [[6th Infantry Division (South Korea)|6th Division]], resulting in a toll of 584 KPA guerrillas (480 killed, 104 captured) and 69 ROKA troops killed, plus 184 wounded.<ref>Bryan, p. 80.</ref> By the spring of 1950, guerrilla activity had mostly subsided; the border, too, was calm.<ref>Bryan, p. 82.</ref>

===Prelude to war (1950)===
By 1949, South Korean and US military actions had reduced indigenous communist guerrillas in the South from 5,000 to 1,000. However, Kim Il Sung believed widespread uprisings had weakened the South Korean military and that a North Korean invasion would be welcomed by much of the South Korean population. Kim began seeking Stalin's support for an invasion in March 1949, traveling to Moscow to persuade him.{{Sfn|Weathersby|2002|pp=3–4}}

Stalin initially did not think the time was right for a war in Korea. PLA forces were still embroiled in the Chinese Civil War, while US forces remained stationed in South Korea.{{Sfn|Weathersby|2002|p=3}} By spring 1950, he believed that the strategic situation had changed: PLA forces under [[Mao Zedong]] had secured final victory, US forces had withdrawn from Korea, and the Soviets [[Soviet atomic bomb project|had detonated their first nuclear bomb]], breaking the US monopoly. As the US had not directly intervened to stop the communists in China, Stalin calculated they would be even less willing to fight in Korea, which had less strategic significance.{{Sfn|Weathersby|2002|pp=9, 10}} The Soviets had cracked the codes used by the US to communicate with their [[Embassy of the United States, Moscow|embassy in Moscow]], and reading dispatches convinced Stalin that Korea did not have the importance to the US that would warrant a nuclear confrontation.{{Sfn|Weathersby|2002|pp=9, 10}} Stalin began a more aggressive strategy in Asia based on these developments, including promising economic and military aid to China through the [[Sino-Soviet Treaty of Friendship, Alliance and Mutual Assistance]].{{Sfn|Weathersby|2002|p=11}}

In April 1950, Stalin permitted Kim to attack the government in the South, under the condition that Mao would agree to send reinforcements if needed.{{Sfn|Weathersby|2002|p=10}} For Kim, this was the fulfillment of his goal to unite Korea. Stalin made it clear Soviet forces would not openly engage in combat, to avoid a direct war with the United States.{{Sfn|Weathersby|2002|p=10}}

Kim met with Mao in May 1950 and differing historical interpretations of the meeting have been put forward. According to Barbara Barnouin and Yu Changgeng, Mao agreed to support Kim despite concerns of American intervention, as China desperately needed the economic and military aid promised by the Soviets.{{Sfn|Barnouin|Yu|2006|pp=139–40}} Kathryn Weathersby cites Soviet documents which said Kim secured Mao's support.{{Sfn|Weathersby|1993|p=29}} Along with Mark O'Neill, she says this accelerated Kim's war preparations.{{Sfn|Weathersby|2002|p=13}}<ref>Mark O'Neill, "Soviet Involvement in the Korean War: A New View from the Soviet-Era Archives", OAH Magazine of History, Spring 2000, p. 21.</ref> [[Chen Jian (academic)|Chen Jian]] argues Mao never seriously challenged Kim's plans and Kim had every reason to inform Stalin that he had obtained Mao's support.<ref name=Jian>{{cite book |last1=Jian |first1=Chen |title=China's Road to the Korean War |date=27 November 1994 |publisher=Columbia University Press |location=New York |isbn=9780231100250}}</ref>{{rp|112}} Citing more recent scholarship, [[Suisheng Zhao|Zhao Suisheng]] contends Mao did not approve of Kim's war proposal and requested verification from Stalin, who did so via a telegram.<ref name=Zhao>{{Cite book |last=Zhao |first=Suisheng |url=https://www.worldcat.org/oclc/1332788951 |title=The dragon roars back : transformational leaders and dynamics of Chinese foreign policy|date=2022|publisher=[[Stanford University Press]] |isbn=978-1-5036-3415-2 |location=Stanford, California |pages=28–29|oclc=1332788951}}</ref>{{rp|28–9}} Mao accepted the decision made by Kim and Stalin to unify Korea but cautioned Kim over possible US intervention.<ref name=Zhao/>{{rp|30}}

Soviet generals with extensive combat experience from World War II were sent to North Korea as the Soviet Advisory Group. They completed plans for attack by May{{Sfn|Weathersby|1993|pp=29–30}} and called for a skirmish to be initiated in the [[Ongjin County, South Hwanghae|Ongjin Peninsula]] on the west coast of Korea. The North Koreans would then launch an attack to capture Seoul and encircle and destroy the ROK. The final stage would involve destroying South Korean government remnants and capturing the rest of South Korea, including the ports.{{Sfn|Weathersby|2002|p=14}}

On 7 June 1950, Kim called for a Korea-wide election on 5–8 August 1950 and a consultative conference in [[Haeju]] on 15–17 June. On 11 June, the North sent three diplomats to the South as a peace overture, which Rhee rejected outright.{{Sfn|Weathersby|2002|p=10}} On 21 June, Kim revised his war plan to involve a general attack across the 38th parallel, rather than a limited operation in Ongjin. Kim was concerned that South Korean agents had learned about the plans and that South Korean forces were strengthening their defenses. Stalin agreed to this change.{{Sfn|Weathersby|2002|p=15}}

While these preparations were underway in the North, there were clashes along the 38th parallel, especially at [[Kaesong]] and Ongjin, many initiated by the South.{{Sfn|Cumings|2005|pp=247–53}}{{Sfn|Stueck|2002|p=71}} The ROK was being trained by the US [[Korean Military Advisory Group]] (KMAG). On the eve of the war, KMAG commander General William Lynn Roberts voiced utmost confidence in the ROK and boasted that any North Korean invasion would merely provide "target practice".{{Sfn|Cumings|2005|pp=255–56}} For his part, Syngman Rhee repeatedly expressed his desire to conquer the North, including when US diplomat [[John Foster Dulles]] visited Korea on 18 June.{{Sfn|Cumings|2005|pp=249–58}}

Though some South Korean and US intelligence officers predicted an attack, similar predictions had been made before and nothing had happened.{{Sfn|Millett|2007|p=17}} The [[Central Intelligence Agency]] noted the southward movement by the KPA but assessed this as a "defensive measure" and concluded an invasion was "unlikely".<ref>{{Cite news |last=Tom Gjelten |date=25 June 2010 |title=CIA Files Show U.S. Blindsided By Korean War |work=[[National Public Radio]] |url=https://www.npr.org/templates/story/story.php?storyId=128092817 |url-status=live |access-date=16 February 2013 |archive-url=https://web.archive.org/web/20130824155650/http://www.npr.org/templates/story/story.php?storyId=128092817 |archive-date=24 August 2013}}</ref> On 23 June UN observers inspected the border and did not detect that war was imminent.<ref>{{Cite book |last=Seth |first=Michael J. |title=A history of Korea: From Antiquity to the Present |title-link=A History of Korea: From Antiquity to the Present |date=2010 |publisher=Rowman & Littlefield |isbn=978-0742567160 |location=Lanham, MD |page=[https://archive.org/details/historykoreafrom00seth/page/n344 324]}}</ref>

===Comparison of forces===
Chinese involvement was extensive from the beginning, building on previous collaboration between the Chinese and Korean communists during the Chinese Civil War. Throughout 1949 and 1950, the Soviets continued arming North Korea. After the communist victory in the Chinese Civil War, ethnic Korean units in the PLA were sent to North Korea.{{Sfn|Millett|2007|p=14}}

In the fall of 1949, two PLA divisions composed mainly of [[Koreans in China|Korean-Chinese]] troops (the [[5th Division (North Korea)|164th]] and [[6th Division (North Korea)|166th]]) entered North Korea, followed by smaller units throughout the rest of 1949. The reinforcement of the KPA with PLA veterans continued into 1950, with the [[12th Division (North Korea)|156th Division]] and several other units of the former Fourth Field Army arriving in February; the PLA 156th Division was reorganized as the KPA 7th Division. By mid-1950, between 50,000 and 70,000 former PLA troops had entered North Korea, forming a significant part of the KPA's strength on the eve of the war's beginning.<ref>{{Cite book |last=Stuecker |first=William |title=Korean War: World History |date=2004 |publisher=University Press of Kentucky |pages=102–103}}</ref> The combat veterans and equipment from China, the tanks, artillery, and aircraft supplied by the Soviets, and rigorous training increased North Korea's military superiority over the South, armed by the U.S. military with mostly small arms, but no heavy weaponry.{{Sfn|Millett|2007|p=15}}

Several generals, such as [[Lee Kwon-mu]], were PLA veterans born to ethnic Koreans in China. While older histories of the conflict often referred to these ethnic Korean PLA veterans as being sent from northern Korea to fight in the Chinese Civil War before being sent back, recent Chinese archival sources studied by Kim Donggill indicate that this was not the case. Rather, the soldiers were indigenous to China, as part of China's longstanding ethnic Korean community, and were recruited to the PLA in the same way as any other Chinese citizen.<ref>Zhihua Shen. [https://books.google.com/books?id=ZWNbDwAAQBAJ&dq=were+indigenous+in+Northeast+China+and+that+the+North+Korean+regime+never+dispatched+soldiers+to+Manchuria&pg=PT306 "A Misunderstood Friendship: Mao Zedong, Kim Il-sung, and Sino–North Korean Relations, 1949–1976".] {{Webarchive|url=https://web.archive.org/web/20230407163505/https://books.google.com/books?id=ZWNbDwAAQBAJ&dq=were+indigenous+in+Northeast+China+and+that+the+North+Korean+regime+never+dispatched+soldiers+to+Manchuria&pg=PT306 |date=7 April 2023 }} Columbia University Press, September 2018.</ref>

According to the first official census in 1949, the population of North Korea numbered 9,620,000,<ref>{{Cite book |last=[[Nicholas Eberstadt|Nick Eberstadt]] |url=https://books.google.com/books?id=72lpTkNcJQ4C&pg=PA61 |title=Policy and Economic Performance in Divided Korea During the Cold War Era: 1945–91 |date=27 September 2017 |publisher=Rowman & Littlefield |isbn=9780844742748 |via=Google Books}}</ref> and by mid-1950, North Korean forces numbered between 150,000 and 200,000 troops, organized into 10 infantry divisions, one tank division, and one air force division, with 210 fighter planes and 280 tanks, who captured scheduled objectives and territory, among them Kaesong, [[Chuncheon]], [[Uijeongbu]], and Ongjin. Their forces included 274 [[T-34#T-34-85|T-34-85]] tanks, 200 artillery pieces, 110 attack bombers, 150 [[Yakovlev|Yak]] fighter planes, and 35 reconnaissance aircraft. In addition to the invasion force, the North had 114 fighters, 78 bombers, 105 T-34-85 tanks, and some 30,000 soldiers stationed in reserve in North Korea.{{Sfn|Appleman|1998|p=}} Although each navy consisted of only several small warships, the North and South Korean navies fought in the war as seaborne artillery for their armies.

In contrast, the South Korean population was estimated at 20&nbsp;million,<ref name="Armstrong"/> but its army was unprepared and ill-equipped. <!-- 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 had 98,000 soldiers (65,000 combat, 33,000 support), no tanks (they had been requested from the U.S. military, but requests were denied), and a 22-plane air force comprising 12 [[Liaison aircraft|liaison-type]] and 10 [[North American T-6 Texan|AT-6]] advanced-trainer airplanes. Large U.S. garrisons and air forces were in Japan,{{Sfn|Appleman|1998|p=17}} but only 200–300 U.S. troops were in Korea.<ref name="james19500625">{{Cite news |last=James |first=Jack |date=25 June 1950 |title=North Koreans invade South Korea |language=en |agency=United Press |url=http://www.upi.com/Archives/1950/06/25/North-Koreans-invade-South-Korea/1012416555294/ |access-date=29 July 2017 |archive-date=6 August 2017 |archive-url=https://web.archive.org/web/20170806141249/https://www.upi.com/Archives/1950/06/25/North-Koreans-invade-South-Korea/1012416555294/ |url-status=live }}</ref>