French campaign against Korea ( 1866 ) The French campaign against Korea of 1866 is also known as Byeong - in yangyo ( " Western disturbance of the byeong - in year " ) . It refers to the French invasion of Ganghwa Island in Korea in retaliation for the earlier execution by Korea ' s Joseon Dynasty of French Catholic priests proselytizing in that country . The encounter , which lasted nearly six weeks , was the first armed encounter between Korea and a Western power . The overall result was a French retreat and a check on its influence in the region . The violent encounter also confirmed Korea in its isolationism for another decade , until Japan forced it to end its isolationism in 1876 through the threat of military force ( see Treaty of Ganghwa ) . Background . Throughout the history of the Joseon Dynasty , Korea maintained a policy of strict isolationism from the outside world ( with the exceptions being interaction with the Qing dynasty and occasional trading with Japan through the island of Tsushima ) . However , it did not succeed entirely in sealing itself off from foreign contact . Catholic missionaires had begun to show an interest in Korea as early as the 16th century with their arrival in China and Japan . Through Korean envoy missions to the Qing court in the 18th century , foreign ideas , including Christianity , began to enter Korea and by the late 18th century Korea had its first native Christians . However , it was only in the mid 19th century that the first western Catholic missionaries began to enter Korea . This was done by stealth , either via the Korean border with Manchuria or the Yellow Sea . These French missionaries of the Paris Foreign Missions Society arrived in Korea in the 1840s to proselytize to a growing Korean flock . Bishop Siméon - François Berneux , appointed in 1856 as head of the infant Korean Catholic church , estimated in 1859 that the number of Korean faithful had reached nearly 17 , 000 . At first , the Korean court turned a blind eye to such incursions . This attitude changed abruptly , however , with the enthronement of the fourteen - year - old King Gojong in 1864 . By Korean tradition , the regency in the case of a minority would go to the ranking dowager queen , In this case , it was the conservative mother of the previous crown prince , who had died before he could ascend the throne . The new king ’ s father , Yi Ha - ung , a wily and ambitious man in his early forties , was given the traditional title of the unreigning father of a king : Heungseon Daewongun , or “ Prince of the Great Court ” . Though the Heungseon Daewongun ’ s authority at court was not official , stemming in fact from the traditional imperative in Confucian societies for sons to obey their fathers , he quickly seized the initiative and began to control state policy . He became one of the most effective and forceful leaders of the 500 - year - old Joseon Dynasty . With the aged dowager regent ’ s blessing , the Heungseon Daewongun set out upon a dual campaign of both strengthening central authority and Korean isolation from the disintegrating traditional order outside its borders . By the time the Heungseon Daewongun assumed de facto control of the government in 1864 there were twelve French Jesuit priests living and preaching in Korea and an estimated 23 , 000 native Korean converts . In January 1866 , Russian ships appeared on the east coast of Korea demanding trading and residency rights in what seemed an echo of the demands made on China by other western powers . Korean Christians with connections at court saw in this an opportunity to advance their cause and suggested an alliance between France and Korea to repel the Russian advances , suggesting further that this alliance could be negotiated through Bishop Berneux . The Heungseon Daewongun seemed open to this idea , but it might have been a ruse to bring the head of the Korean Catholic Church out into the open . Berneux was summoned to the capital , but upon his arrival in February 1866 , he was seized and executed . A round - up then began of the other French Catholic priests and Korean converts . Several factors contributed to the Heungseon Daewongun ‘ s decision to crack down on the Catholics . Perhaps the most obvious was the lesson provided by China , which had apparently reaped nothing but hardship and humiliation from its dealing with the western powers , seen most recently in its disastrous defeat during the Second Opium War . No doubt also fresh in the Heungseon Daewongun ‘ s mind was the example of the Taiping Rebellion in China , which had been infused with Christian doctrines . 1865 had seen poor harvests in Korea as well as social unrest , which may have contributed to a heightened sensitivity to the foreign creed . The crackdown may also have been related to attempts to combat factional cliques at court , where Christianity had made some inroads . As a result of the Korean dragnet all but three of the French missionaries were captured and executed : among them were Bishop Siméon Berneux , Bishop Antoine Daveluy , Father Just de Bretenières , Father Louis Beaulieu , Father Pierre - Henri Dorie , Father Pierre Aumaître , Father Martin - Luc Huin , all of them members of the Paris Foreign Missions Society and canonized by Pope John Paul II on 6 May 1984 . An untold number of Korean Catholics also met their end ( estimations run around 10 , 000 ) , many being executed at a place called Jeoldu - san in Seoul on the banks of the Han River . In late June 1866 , one of the three surviving French missionaries , Father Félix - Claire Ridel , managed to escape via a fishing vessel , thanks to 11 native converts , and make his way to Chefoo ( today known as Yantai ) , China in early July 1866 . Fortuitously in Tianjin at the time of Ridel ‘ s arrival was the commander of the French Far Eastern Squadron , Rear Admiral Pierre - Gustave Roze . Hearing of the massacre and the affront to French national honor , Roze determined to launch a punitive expedition . In this , he was strongly supported by the acting French consul in Peking , Henri de Bellonet . On the French side , there were also compelling reasons behind the decision to launch a punitive expedition . These had to do with increasing violence against Christian missionaries and converts in the Chinese interior , which after the Second Opium War in 1860 had been opened up to westerners . As Korea was a nominal vassal of China , the massacre of westerners and Christians in Korea was seen by diplomatic and military authorities in the context of anti - Western behavior in China . Many believed a firm response to such acts of violence was necessary to maintain national prestige and authority . In response to the event , the French chargé d ' affaires in Beijing , Henri de Bellonet , took a number of intitiatives without consulting with Quai d ' Orsay . Bellonet sent a note to the Zongli Yamen threatening to occupy Korea , and he also gave the French Naval Commander in the Far East , rear admiral Pierre - Gustave Roze instruction to launch a punitive expedition against Korea , to which Roze responded : " Since [ the kingdom of ] Choson killed nine French priests , we shall avenge by killing 9 , 000 Koreans . " Preliminaries ( 10 September – 3 October 1866 ) . Though the French diplomatic and naval authorities in China were eager to launch an expedition , they were stymied by the almost total absence of any detailed information on Korea , including any navigational charts . Prior to the actual expedition , Rear Admiral Roze decided to undertake a smaller surveying expedition along the Korean coast , especially along the waterway leading to the Korean capital of Seoul . This was done in late September and early October 1866 . These preliminaries resulted in some rudimentary navigational charts of the waters around Ganghwa Island and the Han River leading to Seoul . The treacherous nature of these waters , however , also convinced Roze that any movement against the fortified Korean capital with his limited numbers and large hulled vessels was impossible . Instead , he opted to seize and occupy Ganghwa Island , which commanded the entrance to the Han River , in the hopes of blockading the waterway to the capital during the important harvest season and thus forcing demands and reparations on the Korean court . The nature that these demands were to take was never fully determined . In Peking , the French consul Bellonet had made outrageous ( and as it turned out unofficial ) demands that the Korean monarch forfeit his crown and cede sovereignty to France . Such a stance was not in keeping with the more circumspect goals of Rear Admiral Roze , who hoped to force reparations . In any case , the demands of Bellonet were never officially endorsed by the French government of Napoleon III . Bellonet would later be severely reprimanded for his importunate blusterings . Expedition ( 11 October – 12 November 1866 ) . On 11 October , Admiral Roze left Chefoo with one frigate ( " Guerrière " ) , two avisos ( " Kien – Chan " and " Déroulède " ) , two gunboats ( " Lebrethon " and " Tardif " ) and two corvettes ( " Laplace " and " Primauguet " ) , as well as almost 300 Naval Fusiliers from their post in Yokohama , Japan . The total number of French troops is estimated at 800 . On 16 October , a group of 170 Naval Fusiliers landed on Ganghwa island , seized the fortress which controlled the Han river , and occupied the fortified city of Ganghwa itself . On Ganghwa Island , the Naval Fusiliers managed to seize several fortified positions , as well as booty such as flags , cannons , 8 , 000 muskets , 23 boxes of silver ingots and few ones of gold , and various lacquer works , jades , and manuscripts and paintings that comprised the royal library ( Oikyujanggak ) on the island . From his earlier exploratory expedition , Roze knew it was impossible for him to lead a fleet of limited force up the treacherous and shallow Han River to the Korean capital and satisfied himself instead with a “ coup de main ” on the coast . On the mainland across the narrow channel from Ganghwa Island , however , the French offensive was met with stiff resistance from the troops of General Yi Yong - Hui , to whom Roze sent several letters asking for reparation , without success . A major blow to the French expedition came on 26 October , when 120 French Naval Fusiliers landed briefly on the Korean mainland in an attempt to seize a small fortification at Munsusansong , or Mt . Munsu Fort ( depicted in the illustration above ) . As the landing party came ashore they were met by brisk fire from its Korean defenders . If the monastery of Munsusansong fell into French hands , the way to Seoul would be open , so , on 7 November , a second landing party was launched by Roze . 160 Naval Fusiliers attacked Munsusansong defended by 543 Korean " Tiger Hunters . " Three French soldiers were killed and 36 injured before a retreat was called . Except for continued bombing and surveying activity around Ganghwa and the mouth of the Han River , French forces now largely fortified themselves in and around the city of Ganghwa . Roze then sent a new letter , asking for the release of the two remaining French missionaries whom he had reason to believe were imprisoned . No answer was forthcoming , but it became clear from activity seen on the mainland across the narrow straits that Korean forces were mobilizing daily . On 9 November , the French were again checked when they attempted to seize a fortified monastery on the southern coast of Ganghwa called Jeongdeung – sa . Here again stiff Korean resistance , coupled by the overwhelming numerical superiority of the Korean defenders , now numbering 10 000 men , forced a French retreat with dozens of casualties but no deaths . Soon thereafter , with winter approaching and the Korean forces growing stronger , Roze made the strategic decision to evacuate . Before doing so , orders were given to bombard the government buildings on Ganghwa Island and to carry off the varied contents of official storehouses there . It was also learned around this time that the two missing missionaries feared captured in Korea had in fact managed to escape to China . This news contributed to the decision to leave . All told the French suffered three dead and approximately 35 wounded . In retreating from Korea , Roze attempted to lessen the extent of his retreat by stating that with his limited means , there was little more he could have accomplished , but that his actions would have a dissuasive effect upon the Korean government : The European residents in China considered the results of the expedition minimal and demanded unsuccessfully a larger expedition for the following spring . After this expedition , Roze with most his fleet returned to Japan , where they were able to welcome the first French military mission to Japan ( 1867 – 1868 ) in the harbour of Yokohama on 13 January 1867 . The French government ordered the military to leave as a result of heavy losses in the French intervention in Mexico . Ancient Korean books . The books seized by the French at Ganghwa , some 297 volumes of Uigwe , royal court protocols of Korea ' s last ruling monarchy , the Joseon dynasty , dating from between the 14th and 19th centuries , went on to become the core of the Korea collection in the Bibliothèque nationale de France . In 2010 it was revealed that the French government was planning to return the books on a renewable lease to Korea , despite the fact that French law generally prohibited the cession of museum property . In early 2011 South Korean president Lee Myung Bak and French president Nicolas Sarkozy finalized an agreement for the return of all the books on a renewable lease . In June 2011 celebrations were held in the port city of Incheon to commemorate their final return . The collection is now being stored in the National Museum of Korea . Epilogue . In the course of these events , in August 1866 , an American ship " General Sherman " foundered on the coast of Korea . Some of the sailors were massacred , but the United States could not obtain reparations . The United States offered France a combined operation , but the project was abandoned due to the relatively low interest for Korea at that time . An intervention happened in 1871 , with the United States Korean expedition . The Korean government would finally agree to open the country in 1876 , when a fleet of the Imperial Japanese Navy was sent under the orders of Kuroda Kiyotaka , leading to the Treaty of Ganghwa .