Koryo and Yi eras, during which Korea made some noteworthy contributions to world culture. In ceramics, Korean artists elaborated on Chinese styles and techniques, passing them on to Japan, and made an original contribution to coloring in the blues and greens of Korea's unique celadon ware. In painting a similar development took place, with Korean artist-scholars carrying calligraphy in Chinese characters to perfection unmatched—and widely admired—by their Chinese masters. Even where the Koreans did not add distinct contributions, they preserved and passed on to the modern age arts which died out in China, such as the ancient classical court music. In technology and learning there were also some remarkable achievements. Along with skill in metal casting came the use of moveable metal type for printing well before it was known in the West. Shortly thereafter the Koreans invented a phonetic system of writing which, however, did not come into general use until modern times because the yangban wished to preserve their monopoly of learning in the much more complicated Chinese ideographic script. Despite such occasional blighting of native Korean innovations by the overwhelming prestige of Chinese civilization, the Koreans developed a rich, vigorous, and quite distinct culture of their own.
In the late 16th and early 17th centuries, Korea experienced renwed foreign invasions. In 1592 the Japanese launched a full-scale invasion as part of an ambitious plan to conquer China. The Koreans suffered great reverses and the country was ravaged, but Chinese aid and the death of the Japanese ruler, Hideyoshi, saved them. The war produced one of Korea's great national heroes, Admiral Yi Sun-sin, who defeated the Japanese fleet in an engagement in which he used the world's first iron-clad vessel, a tortoise-shaped warship. The abortive Japanese invasion was followed by the successful Manchu conquest of Korea in 1627 and of China in 1644. Korea was to remain a Chinese vassal state under the Manchu dynasty until the end of the 19th century when Russian and Japanese power displaced Chinese influence.
These great invasions reinforced the Koreans' long-standing desire to avoid all unnecessary foreign contacts. Much earlier their kings had supplemented Korea's natural barriers by a small version of China's Great Wall across the peninsula's narrow neck near the 39th parallel. In the 17th century Korea preceded Japan in closing its door to foreigners, and it even discouraged commercial activity and the mining of precious metals to avoid arousing the avarice of foreign interests. Korea tried to remain the "Hermit Kingdom" even after Japan itself applied Perry's tactics, Korea succumbed and in 1876 signed a treaty opening Pusan, and subsequently two other ports to foreign trade. There ensued growing pressure from Western nations—especially from the United States, France, Russia, and Great Britain—which evoked considerable internal dissension over how much contact should be allowed, and with whom. Powerful and bitterly hostile factions aligned themselves either behind Korea's traditional patron and protector, China, or one of the rival neighbors, Russia or Japan. China hastened to have the Koreans open relations with other Western powers to offset Japanese predominance, at the same time seeing that China's suzerainty over Korea was recognized.
In 1894 an antiforeign rebellion led to Chinese and Japanese intervention and subsequently to the Sino-Japanese war. Victorious Japan forced China to abandon any claim to a special position in Korea. Conservative, anti-Japanese forces within the country then turned to Russia for support, and helped the Russians gain concessions for raw materials in northern Korea. The Russians helped Korea reorganize its finances and its army and then moved to acquire naval bases on the southeastern and southwestern corners of the peninsula. Although the British and Japanese, fearing the establishment of Russian control of the Korea Strait and the entrance to the Yellow Sea, jointly blocked the Russian move, Russia continued to pursue its ambitions. The Japanese ultimately responded by launching a surprise attack in February 1904 on the Russian fleet. Engagements were fought off the Korean coasts and Japan made full use of Korea as a base of operations, despite Korea's declaration of neutrality. After Russia's defeat in 1905, Korea became
