Marlborough College Summer School

Destined to Fail? How the division of Korea led to the Korean War

Rowena Hammal explains why the Korean War broke out in 1950.

F4U-5 Corsairs provide close air support to U.S. Marines fighting Chinese forces, December 1950.If there is one issue on which historians should be able to agree, it is that the artificial division of a country usually creates more problems than it solves. The twentieth century is full of examples: Ireland in 1921, Germany after each of the two world wars, the partition of India in 1947, the creation of Israel in 1948. Korea’s division led to a war which proved as serious as any of the difficulties encountered by those nations. A unique set of internal and external factors combined to create a conflict which almost precipitated a nuclear war. President Truman wrote in despair in December 1950, ‘I’ve worked for peace for five years and six months and it looks like World War III is here.’

Fortunately, Truman was proved wrong. The US was able to restrain itself from using the atomic bomb, and the USSR decided not to become fully involved in the war. Instead, North Korean and later Chinese troops fought a conventional war against the United Nations forces led by the US. International losses were heavy: up to 1 million Chinese, 33,000 Americans, and 686 British soldiers were killed. However, for Korea the war was truly cataclysmic, leaving an estimated 3 million civilians (approximately a tenth of the population) and 500,000 soldiers dead (from North and South), and ending with a stalemate which has left the country divided to this day. This article will examine the division of Korea into North and South, and consider how this led to war.

A Line on a Map

The division of Korea in August 1945 was a practical response to the situation in East Asia at the end of the Second World War. The USSR had entered the war against Japan a week previously, and Soviet troops were marching south through Japanese-controlled Korea when news came of Japan’s surrender. Japan’s defeat had occurred sooner than anticipated by the US command, which did not yet have troops in Korea, so in order to prevent the USSR from seizing control of the whole country (as had recently happened in Eastern Europe), it was agreed that the Soviets and the Americans would divide Korea between them. Two US colonels were given half an hour with a map and a ruler, and decided on the 38th parallel as it gave the US control of the capital, Seoul, and was already printed on most maps of Korea.

The line cut across a thousand years of Korea’s history as a unified nation. It also ran counter to economic logic, as the resulting halves were interdependent; industry was concentrated in the north, while the south was predominantly given over to agriculture. Most importantly, the division flew in the face of the wishes of the Korean population. Koreans had suffered under Japanese colonial rule since 1910, and by 1945 Korean nationalism was at fever pitch. Korean independence was, in fact, almost the only thing which the vast majority of Koreans agreed on. The country had yet to modernise its economy, and was effectively still a feudal society with vast areas of land concentrated in the hands of a privileged elite, many of whom had worked with the hated Japanese administration. Korean politics was therefore dominated by left-wing groups, some of which where Communist, calling for land reform and the punishment of collaborators, and by right-wing elements who hoped to maintain the status quo within an independent Korea.

An opportunity to build consensus across the political divide was lost in 1945 when the US refused to work with the Korean People’s Republic (KPR), a coalition of parties which included rightists, moderates, and Communists, all keen to provide a united front so that government could be passed into Korean hands. However, the US was determined that Korea should be prepared for independence via a long trusteeship, principally to ensure that Communism would not take root. The KPR declined to accept American authority, claiming that it was the official government, and as a result it was first ignored and then outlawed by the American Military Government. The differences between members of the KPR made it an inherently unstable organisation, but it would surely have been a good starting point from which to work toward a united self-governing Korea.


Korea’s political landscape was complex, and the division of the country only served to polarise the right and left further. Spontaneous ‘People’s Committees’ sprang up across Korea, formed by communities seeking control at a local level. In the North the USSR encouraged these groups as a recruiting vehicle for the Communists. However, the US viewed left-wing activity as a threat, particularly given the presence of Communists in many People’s Committees. The American Military Government, headed by General Hodge, did not distinguish between home-grown Communism , more a product of anti-imperialism than Marxism, and Soviet-controlled Communism . People’s Committees were therefore shut down in the South and under US rule left-wing activity was heavily restricted.

Hodge knew little about Korea, and did not even have anyone in his staff who could translate Korean. As a result he depended heavily on members of the aristocratic elite who had been educated in English, an association which only deepened his suspicion of leftists. In an attempt to unify the South under a pro-American figurehead, the US arranged for the nationalist septuagenarian Syngman Rhee to return to Korea from the USA, where he had been in exile for over 30 years. This was a miscalculation. Rhee was so virulently anti-Communist that US censors had to screen his speeches to remove the most inflammatory remarks. Far from being a unifying figure, Rhee would first help to scupper negotiations for the reunification of Korea, and then, having achieved the Presidency, go on to create a right-wing police state in which political opponents were arrested in their thousands.

The Soviet-controlled North was moulded into a totalitarian state under the leadership of Kim Il Sung, a young Communist guerrilla fighter who was brought in by the USSR in October 1945. The Communist policy of land redistribution was popular, as was the fact that the North was nominally being run by a Korean, and by the late 1940s up to a quarter of the adult population were members of the North Korean Communist Party. However, the USSR’s desire to create an obedient satellite state led to the ‘re-education’ of those who did not conform politically, and many thousands of right-leaning Koreans fled to the South. Homogeneity within the Korean Communist Party was achieved by expelling members who challenged Kim’s leadership.

Thus it was that, under US and Soviet control, Korea was transformed from a single nation with political fissures running horizontally through society, into a peninsula with a vertical polarisation between North and South. This suited both the US and the USSR within the context of the Cold War, and as Adrian Buzo has written: ‘… their policies derived from the nature of their mission: they were occupying powers, not nation builders.’ The historian Richard Whelan has contrasted Korea’s situation with that of Austria, a country divided between American-British, French, and Russian zones after the Second World War, but which was able to gain independence in 1955. He writes: ‘the difference was that in Austria the dominant parties of the left and the right were moderate enough to be able to form a stable coalition. In Austria the most powerful political forces were centripetal, in Korea centrifugal.’

Peaceful Reunification?

The division of Korea had always been intended to be temporary, the plan being to form a provisional government to unify the country. The government would then govern under the trusteeship of the Soviet- US Joint Commission. This was agreed in the Moscow Accords of December 1945, but by September 1947 it was clear that the Joint Commission was unworkable. North and South were now so opposed to each other, and so tightly bound to the superpowers, that talks on a provisional government failed. The US allowed Rhee’s Representative Democratic Council (RDC) to attend the talks, despite a previous agreement that groups who were anti-trusteeship would be excluded. The RDC was campaigning against trusteeship, and the USSR therefore refused to recognise it. The USA would not consider removing the RDC because, as a right-wing grouping, its inclusion was required to produce a provisional government that the US could accept. There were no moderate Korean political parties, and in the absence of the RDC any government would have been dominated by Communists and leftists. America’s patronage of Rhee, and support of authoritarian rightists, had ultimately prevented reunification under trusteeship: ironic given that the US had designed the scheme.

Following the breakdown of talks, the USSR suggested that both occupying powers withdraw their armies and leave the Koreans to come to some arrangement. The result would probably have been civil war resulting in a Communist victory. However, in an attempt to save the situation Truman referred the matter to the United Nations, which set up a United Nations Temporary Commission on Korea (UNTCOK) to oversee democratic elections for a fully independent Korean government. This was Korea’s final chance for peaceful reunification, but it was squandered. The USSR would not allow elections to go ahead as it feared that the 9 million Koreans in the North would be outvoted by the 16 million Koreans in the South, resulting in the formation of a pro-American government. In May 1948, UNTCOK oversaw elections in the South which gave the Presidency of the new Republic of Korea to Syngman Rhee. The North held its own elections in August 1948 which, unsurprisingly, placed Kim Il Sung at the head of the new Democratic People’s Republic of Korea (DPRK). The division of Korea was now permanent and polarisation was absolute. War was now the only way to achieve reunification.


From their inception, the governments of both South Korea and North Korea openly advocated military reunification. Kim claimed that his government represented the whole of Korea, not simply the North, and provided support to guerrilla activity in the South. Meanwhile, Syngman Rhee frequently alluded to an invasion, which so concerned the Americans that they restricted the amount of military aid given to South Korea. The historian Bruce Cummings has shown that border fighting took place in a series of battles across the 38th Parallel, particularly in the summer of 1949. It appears that the South was as much to blame as the North in these incidents, and may even have initiated more conflicts than the North. Both Korean leaders were committed nationalists, harnessing popular support from their commitment to unification. In January 1950 Kim told the Soviet ambassador: ‘Lately I do not sleep at night. If the matter of the liberation of the people of the southern portion of Korea and the unification of the country is drawn out, then I can lose the trust of the people of Korea.’


Each side was therefore keen to launch a civil war, but they were restrained by their dependence on the US and the USSR. The superpowers provided massive amounts of aid to their Korean protégés, ensuring that they retained influence in Korea. The US would not support an invasion, and without military and financial support South Korea was unable to act. Far from being a model of liberty and capitalism, this ‘tight little dictatorship run as a police state’ (US journalist A.T. Steele, writing in 1949) was racked by economic problems and internal dissent. In the North, Kim needed Stalin’s backing to launch an invasion, and initially the Soviet leader was unwilling to help, fearing that any invasion might prompt American intervention. Evidence from the Soviet archives shows that Kim lobbied Stalin from March 1949, when his invasion request was flatly turned down, through to January 1950, when Stalin began arming North Korea in preparation for the attack.

Four key factors caused Stalin to change his mind. Firstly, the USA pulled its troops out of South Korea in June 1949, leaving only 500 military advisers behind. Secondly, the USSR acquired the atomic bomb in August 1949, meaning that any attempt by the US to intervene in a civil war in Korea now carried far greater risks. Thirdly, in October 1949 Mao’s Communists emerged victorious from the Chinese civil war, a sea change in Asian politics and one which the US made no direct attempt to prevent. Fourthly, additional evidence of the US’s unwillingness to intervene militarily in Asia was provided by Secretary of State Dean Acheson’s National Press Club Speech in January 1950, in which he described a ‘defensive perimeter’ around the USA. It included Japan, the Philippines, and the Aleutians, but Korea was excluded. Stalin was prepared to support the attack, provided that Mao gave his consent to conflict on China’s doorstep. Mao had received significant help from North Korea in the civil war, some tens of thousands of Koreans having fought on the side of the Communists, and he therefore agreed to Kim’s invasion.

Widening Participation

Stalin was not the prime mover behind the outbreak of war, but rather the sponsor of Kim’s ambition to reunite his country. However, the US rightly surmised that the USSR was involved and, to Stalin and Kim’s great surprise, took action to prevent Korea from being overrun by Communists. Truman needed to ‘draw the line’ in Korea to maintain his containment policy and prevent the USSR from expanding in Asia as it had in Eastern Europe. The US was keen to legitimise its decision to support South Korea, and by the 27th June had obtained backing from the UN. (The USSR was unable to veto the resolution at the Security Council. It was boycotting the UN because China had been denied membership.) The entry of the US and UN into Korea would transform the conflict from a civil war to an international one. In September 1950 the US would take the decision to ‘roll-back’ Communist forces, with the aim of pushing them out of North Korea entirely. The decision to push up to the Yalu River, Korea’s border with China, would precipitate a massive military response from the Chinese and the start of ‘an entirely new war’ (General MacArthur, commander of UN forces).


The Korean War developed into a major Cold War conflict, a war which neither the Americans nor the Chinese could afford to lose. It did not begin as such. Rather, it began as a civil war, albeit with the involvement of the USSR and China. The pressure for war came from Koreans, both north and south of the border. It was a war which seemed inevitable to many at the time, including American observers, given the desire for reunification emanating from all levels of society. The division of Korea in 1945 had ignored the nation’s long history, economic situation, and public opinion. Peaceful reunification had been ruled out by the polarisation of North and South under Soviet and American occupation, and then by the aggressive regimes supported by the superpowers. Hence by 1948 war was effectively inevitable. The timing of the war would be determined by the USSR, and the nature and scale of the fighting would ultimately be determined by US and Chinese intervention, but at heart this was a Korean war: the result of the nation’s arbitrary division.