The decade of Regent Taewon-gun, alias Yi Ha-ung, has been known in Korean history for its closed door policy. His adamant refusal to open the country to the rising Western nations in the mid-nineteenth century was a major factor in delaying the modernization of Korea for more than ten years. A closer look, however, reveals that he was not in the position to deny the Western civilization in toto. Rather he was a man of reasonably open-minded trend of the period, absorbing ideas both from the traditions of Sirhak scholarship and of Christianity. Taewon-gun was a man totally different from those die-hard conservatives including Yi Hangno and Choe Ikhyon, who considered everything Western as "wicked." For one thing Taewon-gun used to have a close tie with some of the Sirhak scholars including Kim Chong-hi. He used to visit Kim while the scholar was alive in the mid-nineteenth century, when he had also met several less illustrious scholars of the Sirhak tradition including Kang Wi, Sin Kwanho, Pak Kyusu and so forth. As a matter of fact, after Taewon-gun became the actual ruler of the country, Sin Kwanho served as one of the key members of the Taewon-gun government along with Pak Kyusu. As we shall see promptly, Sin served as the Chief Commander (Hullyon taejang) when he invented new types of gun, and Pak as known today as the father of the reformist thoughts of the eighties. Taewon-gun is also known to have some relations with Christianity before 1864. Not only he knew about the eight foreign missionaries active in the Korean peninsula, but also he had Christian believers in his family including his own wife and one of his daughters. Because of such a background of Taewon-gun, the earlier period of his dominance was a honeymooning period between the Christians and himself. For both parties, a search was made to guarantee cohabitation in their common interest area, namely in Taewon-gun's wish to borrow military assistance from France to stop the infiltrating Russians of the north in the early sixties. Nevertheless, Taewon-gun suddenly changed his attitude in the early days of 1866 to thoroughly suppress Christianity and to raise the banner of close-door policy thereafter. The sudden shift in his policy was the result of purely political domain, with little to do with his ambition to introduce and learn the superior science and technology of the West. Since he could not reach, as every leader of the period could not, the realization that the Western science and technology was not necessarily a part of the Western Christianity at the time, his self-contradicting policy is understandable. Under the given circumstances the introduction of Western science and technology in the period was inescapably partial, peacemeal, and indirect. Since no foreigner was allowed to enter the country and no Korean was permitted to visit the Westerners, the only contact of the Koreans with the modern science and technology was through the partial and incomplete rendition of the Western knowledge into Chinese books. Particularly after the War of 1866 against the French (Pyongin yangyo) Taewon-gun pressed the military reforms of all kinds along the Western weaponry. To cope with the new era of guns and powder, some institutional changes were made. New methods of making gun-powder was taught and new guns styled after the Western types were produced. In their efforts for making new weapons, several Chinese books about the West were sources of their inspirations. Actually when Sin Kwanho made a marine gun (Suroep'o) in 1867 he used the model illustrated in Wei Yuan's Hai-kuo tu-chih(1842). Partially western style guns were being made from earlier period. But evidences show that the products were not anything comparable with the original Western models, because only the outward shapes were imitated without mastery of necessary skills in metallurgy. Similar efforts were continued throughout the earlier period of his rule. For instance he ordered three new ships built in 1867 possibly utilizing the Koreans' meager knowledge of the Western war-ships. One of the three war-ships might have been the first Korean steam-ship. Tradition has it that the Koreans rebuilt the steam-engine of the General Sherman, a Western boat destroyed by the Koreans in the Taedong River in 1866. The rebuilt engine was attached to a new boat for a test cruise in the Han River in 1867. But because they did not have any coal, they had to burn charcoal instead to heat the boiler. Obviously the speed of the first Korean steam-boat was not very impressive to the watchers including the Regent himself, because the speed was something like a dozen feet for a full minute. Also in this period a "floating boat"(pison) was improvised by attaching bundles of crane feathers around the boat, and an anti-bullet vest was also made of a very thick material made of thirteen layers of cotton. Both proved to be hopeless failures. When we compare Taewon-gun with his daughter-in-law, Queen Min, we find him a remarkable man with much less propensity toward magical adventures of which the Queen was so fond. In beginning months of his rule Taewon-gun also demonstrated his share of superstition in his indulgence in geomansic episodes recorded in history. Other than this, however, he showed a generously rational attitude toward the Western science and technology. With all his rational attitude to the Western science and technology, Korea in his period failed to absorb modern science and technology. In final anlysis we have to conclude that his efforts to learn modern science and technology failed simply because of his closed-door policy. His policy had successfully curtailed the slow infiltration of modern science and technology through the the hands of the Western missionaries as much as the more aggressive learning of it for the part of the Sirhak scholars in the period. Valuable efforts by Choe Han-gi notwithstanding, the Sirhak tradition suffered greatly during his rule, which was decisively adverse to the introduction of Western science.