Why did no European power colonize Korea?

They tried, but it was never a military possibility. The US, France, and, to a far greater extent, Russia, attempted to impose their will on Korea but failed due to either Korean resolve, the threat of Qing or Japanese intervention, or both.

Western imperialism in Asia had not one, but two peaks. In 1860, the Qing military, distracted by civil war, underfunded, mired in corruption, and over-bureaucratized utterly failed to stop the British and French from occupying Beijing and burning the Summer Palace. This disaster led a clique of reformers led by Empress Dowager Ci Xi, Prince Gong, and Zeng Guofan to seize power in a coup.

For the next 25 years, the “Tongzhi Restoration” clique defeated countless rebellions, reconquered Xinjiang, and built an army that defeated the Russians in 1878 and the French in 1885. The Qing military resurgence in this period was for a long time underappreciated by historians but was fully appreciated by contemporaries who perceived the country to be a rising power. As a result, there were effectively no Western colonial accomplishments in Northeast Asia for the entirety of this era – the aggressive gunboat diplomacy of the 1850s and early 1860s was replaced by limited expeditions, moderated by the threat of Qing intervention.

The two such expeditions to Korea – the French and American Ganghwa expeditions – by diplomatic necessity committed a very small force for a short amount of time. While both militarily succeeded in conquering Ganghwa island off the coast of Seoul, neither deployed enough forces to capture the capital itself.

The Korean court – far more conservative (and resolute) than that of Japan or China – obstinately refused to offer concessions to either party, and both countries were forced to back down. It is critical to note when evaluating the small scale of these expeditions that Korea, unlike Southeast Asia, was being subjected at the time to Qing imperialism.

The Qing court was in the process of revising Korea’s loose tributary status to that of a Western-style colonial dependency, acquiring commercial concessions, and intermittently deploying troops. Any larger or more ambitious adventure would certainly have led to a wider conflict, as the French expedition to Vietnam triggered the Sino-French War.

Western power in Asia would witness a “second peak” following the Qing’s humiliation in the First-Sino Japanese War. Until recently, scholarship surrounding the decline of Chinese forces between 1885 and 1895 has been limited, but research over the past few years has allowed a more coherent picture. Following the Empress Dowager’s retirement in 1889, Guangxu Emperor, influenced by his chief advisor, Grand Tutor Weng, slashed military funding considerably.

The rationale for the cuts was twofold: first, Guangxu’s clique did not share the Empress Dowager’s fear of Japan. Second, the army and navy were used by Ci Xi and her allies as conduits to embezzle funds. The result was a total halt to naval buildup and an underpaid army which, in the words of a contemporary journalist, “had no inducement to stay and be killed”. Equally important was Japan’s excellent espionage work: Tokyo’s spies had procured an asset in the Qing telegraph office, Chang Yinhuan, who referred to them all Qing troop movements.

Far from lionizing Japan, the outcome of the Sino-Japanese War convinced European powers that Asian countries, in general, were harmless. The much-feared China threat before 1894 rested on the assumption that even a marginally competent China, due to its immense manpower, could prevail over Western powers in a long war.

Japan, a country with a smaller population than every single Western Great Power, was no threat even if it achieved equal military competence to Westerners. At the time, the idea that Japanese soldiers and officers would exceed the capabilities of the Russians a decade later was inconceivable: the Japanese army, Western-advised until 1888, was widely perceived to be a passable but still inferior clone of Europe’s forces.

After the war, European powers re-asserted themselves in Northeast Asia, briefly leading to the possibility of Korea becoming a protectorate of Russia. Britain, France, Germany, and Russia forced the Qing to grant them new concessions, perceiving a general power vacuum in the region.

Russia, which stayed out of Korea out of fear of Qing in the decade and a half following their defeat at Ili, perceived no such threat from Japan and turned the Korean court into an effective client state. The small Korean army fell under Russian command, and Russian commercial interests were dominant in the northern half of the country. For his part, Korean King-cum-Emperor Gojong, having lost Chinese protection, was all too willing to assent to counterbalance Japan.

Japan’s upset victory in the Russo-Japanese War put an end to this short-lived Russian influence project and placed the Korean peninsula firmly under Japanese control. In 1905, the Eulsa Treaty made the country a Japanese protectorate, while the Taft-Katsura Agreement procured American support for Japanese occupation, after which point any further colonial penetration by other powers became impossible.