The Imjin War: Japan's Sixteenth-Century Invasion of Korea and Attempt to Conquer China

by Samuel Hawley

  The squadrons that Yi Sun-sin had met and annihilated in June of 1592 were thus not the cream of the Japanese navy, if such can be said to have existed. They were disorganized bands of mainly transport ships that were probing westward with the intention of securing the Korean coastline between Pusan and the Yellow Sea, and doing a little looting along the way. They did not expect to encounter much resistance from the Koreans, certainly not in the form of formidable armored warships, and when they did they beat a hasty retreat.

  The loss of more than forty of their ships awoke the Japanese to the fact that the Korean navy was not yet beaten. It was still not seen as posing a very great threat, however, for according to the reports brought back to Pusan the Koreans had fewer than fifty large and medium-sized ships. Still, the problem had to be dealt with. The southern coastline had to be secured so that Japanese ships could begin ferrying reinforcements and supplies north via the Yellow Sea to the advancing front. A second operation to stamp out resistance along the southern coast was therefore launched in early July. This time it would comprise not just transports. There would be warships under the command of such maritime daimyo as Kurushima Michiyuki, Kamei Korenori, and Wakizaka Yasuharu.

  * * *

  Cholla Left Navy Commander Yi Sun-sin spent nearly three weeks at his home port of Yosu following the Okpo campaign, resting his men, repairing his ships, and planning a second operation against the Japanese. The hiatus was finally broken when word arrived from Won Kyun, based farther east in Kyongsang Province, that Japanese naval forces were beginning to advance in earnest along the southern coast. They were already as far as Sachon, dangerously close to Commander Yi’s home port. Yi knew that Yosu could not stand against a land attack and that the only way to forestall the Japanese was to attack them at sea before they advanced any farther. Not waiting for the arrival of Yi Ok-ki’s Cholla Right fleet, Yi Sun-sin immediately sailed east on July 8 with just twenty-three warships. This time he discarded the small sea ear fishing boats—he had found them of minimal use during the previous campaign—but added something altogether more formidable: the kobukson, or turtle ship.

  Yi and his master shipbuilder Na Tae-yong did not invent the kobukson as is often assumed. It had been developed some two centuries before, to combat the wako pirates then causing havoc along Korea’s coasts. Its first appears in the historical record in 1413, in a brief report in the annals of King Taejong of the monarch viewing a mock battle between a kobukson and a Japanese warship.[238] The vessel by all accounts proved highly effective. Over the course of the next century and a half, however, the value of the kobukson seems to have been forgotten as Korea’s military preparedness waned, until it finally became just a dim memory preserved in history books.

  It was this dim memory that Yi Sun-sin resurrected and refined. No contemporary account exists of exactly what the vessel he built looked like. Yi himself has left us only this vague description:

  Previously, foreseeing the Japanese invasion, I had had a Turtle Ship specially built with a dragon’s head, from whose mouth we could fire our cannons, and with iron spikes on its back to pierce the enemy’s feet when they tried to board. Because it is in the shape of a turtle, our men can look out from inside, but the enemy cannot look in from outside. It moves so swiftly that it can plunge into the midst of even many hundreds of enemy vessels in any weather to attack them with cannon balls and fire-throwers.[239]

  Yi’s nephew, Yi Pun, who served under the commander during the latter part of the war, added a few more details in the biography of his uncle that he subsequently wrote:

  He invented a warship of the same size as a board-roofed vessel [panokson]. On its upper deck were driven iron spikes to pierce the feet of any enemy fighters jumping on it. The only opening was a narrow passage in the shape of a cross on the surface for its crew to traverse freely. At the bow was a Dragon-head in whose mouth were the muzzles of guns, and another gun was at the stern. There were six gun ports each, port and starboard, on the lower decks. Since it was built in the shape of a big sea turtle, it was called Kobuk-son (Turtle Ship). When engaging the enemy wooden vessels in a battle, the upper deck was covered with straw mats to conceal the spikes. It rode the waves swiftly in all winds and its cannon balls and fire arrows sent destruction to the enemy targets as it darted at the front, leading our fleet to victory in all battles.[240]

  The description in Sonjo sujong sillok, the revised annals of King Sonjo compiled some fifty years after the war, is so similar to Yi Pun’s that it was likely based upon it.[241]

  These two passages contain virtually all the information we have of the turtle ship from individuals who actually saw one or heard of it firsthand. For more detail it is necessary to move forward to a description of the vessel written two hundred years later for inclusion in The Collected Works of Yi Sun-sin, compiled and published in 1795.

  Figure 7: The Kyongsang Coast

  The editors of this work listed the sizes of the kobukson’s key timbers, the number of cabins, ports, and oars, and various other bits of information like the exact size of the dragon’s head adorning the bow. Adding this information to Yi Sun-sin’s and Yi Pun’s descriptions, the following picture of the turtle ship emerges. It was roughly twenty-eight meters long, nine meters wide, and six meters high from its flat, keeled bottom to the top of its roof. It was, in other words, a fairly large ship for its day, but sat quite low in the water, allowing it to come in under the high “castles” of Japanese fighting ships and blast away at their hulls near the waterline. A sloping roof of stout planks was laid on top of the bulwarks, totally encasing the vessel like the shell of a turtle, with just a narrow slit at the apex to allow a mast and sail to be raised and lowered. The roof was covered with iron spikes to disable enemy attackers if they attempted to board. The primary means of propulsion, particularly in battle, when speed and maneuverability were of prime importance, were twenty sculling oars, ten per side, each oar handled by two or three men. Cannons pointed out from loopholes on port and starboard, bow and stern, about fifteen guns in all. The interior of the vessel, finally, consisted of two decks: a lower propulsion deck for the oarsmen, and an upper fighting deck for archers launching regular and fire arrows and for gun crews manning chonja (heaven), chija (earth), hyonja (black), and hwangja (yellow) cannons mounted on wooden carriages.[242]

  Yi Pun’s assertion that straw mats were laid upon the roof to disguise the spikes might seem at first unlikely as this would have turned the kobukson into a floating tinderbox, ready to be set alight by the many fire arrows used in sea battles at that time. Keeping the mats soaked with seawater, however, would not only have solved this problem, but additionally would have made the roof fire retardant.

  By far the biggest point of contention regarding the turtle ship is whether or not its spiked roof was covered with iron plates. Early English-language accounts of the Imjin War usually described it as such, typically adding that it was the world’s first ironclad ship. This latter claim is certainly not true. Fifteen years earlier in Japan, Oda Nobunaga had employed ships armored in some manner with iron against the fleet of the rival Mori clan in Osaka Bay, a technological innovation that the Japanese never capitalized on. Indeed, it is unlikely that Yi Sun-sin’s turtle ship was iron plated at all. The evidence to support this claim does not exist. An ironclad ship would have been something new in Korea in the late sixteenth century and would certainly have excited comment somewhere in the many letters and diaries and reports that survive from this period. Yet Yi himself makes no mention in either his diary or his reports to court of any sort of iron plating covering the roof of his kobukson. Nor does his nephew Yi Pun in his biography of the admiral. Nor does Korean prime minister Yu Song-nyong in his own account of the war. (Yu describes the kobukson as “Covered by wooden planks on top.”[243]) Nor do the annals of King Sonjo, that exhaustive compilation of dispatches, reports, conversations, and comments from this period running into the many thousands of pages. In fact, no mention exists in any
contemporary Korean account of the war that the turtle ship was ironclad.[244]

  Another factor weighing against iron plating is the difficulty that Yi Sun-sin would have faced in acquiring enough metal to cover even one large ship, let alone several. In his treatise in support of the iron plating theory, Bak Hae-ill, extrapolating from the iron cladding on the doors of Seoul’s fifteenth-century Namdaemun Gate, estimates that six tons of metal would have been needed to cover the roof of one turtle ship with plates two to three millimeters thick.[245] That is a lot of iron, the equivalent of the vessel’s entire complement of cannons. Considering that Yi Sun-sin received so little support from the government and had to scrounge most of the materials he needed to repair and outfit his fleet, the acquisition and use of such a load of iron would have been difficult, and probably would have been considered more usefully employed in the casting of additional cannons, enough to outfit an entire new ship. Yi himself considered it worth mentioning in his diary the relatively insignificant amount of fifty pounds of iron that he sent to Cholla Right Navy Commander Yi Ok-ki as a gift in early 1592.[246] And yet nowhere does he mention acquiring and using six tons of the metal—that’s twelve thousand pounds—to cover his turtle ship.

  Such a lack of evidence cannot rule out completely the possibility that the turtle ship had some sort of iron plating on its roof. But it does seem to weigh heavily against it. Until further information comes to light to the contrary, the likeliest conclusion is that Yi Sun-sin’s turtle ship was armored only insofar as it was constructed of heavy timbers and covered with a thick plank roof studded with iron spikes—which against the light guns of the Japanese was armor enough.[247]

  If there is no evidence in the historical record that the kobukson was ironclad, where did this idea come from? One hypothesis is that it may have come from the West. The first tales of Yi Sun-sin and his turtle ship to reach Europe and the United States were carried back by Westerners who visited Korea as it started to open to the world in the late 1870s. A British naval expedition to Korea in 1883, for example, included an account of the curious vessel in its official report, which subsequently appeared in a Chicago newspaper.[248] Ensign George Foulk of the U.S. Navy heard similar stories during his wide-ranging travels on the peninsula in 1884, and actually saw what locals claimed to be the ribs of a turtle ship lying in the sand at Kosong on the coast of Kyongsang Province.[249] To a Westerner of this period, these descriptions of an indestructible warship with a roof like a turtle’s back would have conjured up an immediate association: the Confederate ironclad the Virginia (a.k.a. the Merrimac) and its Union counterpart the Monitor which had battled each other in the American Civil War some twenty years before. It is possible that the inevitable comparison of Yi’s warship to these two ironclads of recent memory led to the assumption that it too was fitted with iron plates and not simply “armored” with a heavy timber shell. This progression from casual comparison to statement of fact can be roughly charted. In his 1892 account of Hideyoshi’s invasion, George Heber Jones wrote that “aided by his famous ‘Tortoise Boat,’ a prototype of the ‘Monitor’ of the American Rebellion, [Yi Sun-sin] literally swept [the Japanese] off the coast waters of the peninsula.”[250] William Griffis took this a step further in 1894 in Corea. The Hermit Kingdom, describing Yi’s ship as “apparently covered with metal.”[251] By 1905 the transformation to fact was complete. “Its greatest peculiarity,” wrote Homer Hulbert of the turtle ship in his History of Korea, “was a curved deck of iron plates.... [I]t anticipated by nearly three hundred years the ironclad war ship.”[252]

  Yi Sun-sin’s armored kobukson thus went from being regarded as “like” the ironclads of the American Civil War to being itself an ironclad, an assumption that gained weight the more often it appeared in print. It was an assumption that was readily accepted by the Koreans, who were then trying to deal with a flood of Western pressures and innovations that was making them appear to the world as a weak and backward people. In this atmosphere of vulnerability the idea that a Korean had invented the ironclad ship nearly three centuries before was immensely appealing, for it demonstrated that Korea was not a backward country, but in some things had actually preceded the West. The belief that Yi Sun-sin’s kobukson was an ironclad ship thus resides firmly in the consciousness of Koreans today, despite the lack of evidence to support the claim, for it is more than just a historical artifact. It is a symbol of national pride.

  One of the more distinctive features of the turtle ship was the impressive dragon’s head that adorned its bow. This head is depicted in modern-day models and illustrations in an attractive upraised position like a cobra rearing to strike, together with the explanation that smoke from burning gunpowder and sulfur was emitted from the dragon’s mouth to terrorize the enemy and obscure the vessel’s movements. In his own description of the craft, however, Yi Sun-sin states that a cannon could be fired through the mouth, something that could not have been done if the head was upraised. It must have projected straight out from the bow in a less majestic manner.

  The genesis of these two images is found in The Collected Works of Yi Sun-sin published in 1795, a compilation of Yi’s war diary and official dispatches, additional accounts penned many years after his death, and commentary written by the editors themselves. Among this latter material are two illustrations of the turtle ship. The first, labeled tongjeyong kobukson, is an estimation of what the vessel originally looked like in the early fifteenth century, with a dragon’s head projecting straight out from the bow. The second illustration, labeled Cholla chwasuyong kobukson, depicts a turtle ship that was still extant in 1795, anchored at Yosu, home port of the Cholla Left Navy, which was said to resemble the revised turtle ship Yi Sun-sin developed in 1592. It has two dragon heads: an upraised one above, and a downward-projecting one below that seems to emerge from the bow just beneath the fighting deck where the cannons would have been. If a vessel resembling the Cholla chwasuyong kobukson did see service in the Imjin War, then it may have been a later innovation, one of the several additional turtle ships Yi had constructed after 1592. The editors of Yi’s Collected Works may also be wrong: the illustration may depict a vessel built long after the war. The only description that Yi himself has left us indicates that the dragon’s head on his turtle ship projected straight out from the bow, as on the tongjeyong kobukson. If his ship had two heads like the Cholla chwasuyong kobukson, then the lower head must have projected forward and been positioned higher, at the gun deck.[253]

  * * *

  After leaving his home port of Yosu on July 8, Yi Sun-sin met Won Kyun at Noryang Bay and the two men once again formed a combined fleet. From there they headed toward Sachon, a port dangerously close to the Cholla border, where according to reports Japanese ships had already arrived.

  By this point Yi evidently had little use for the Kyongsang Right Navy commander and his fleet of four ships, for he gave Won the job of “finding Japanese killed by arrows or bullets anywhere on the battle-ground, and [cutting] off their heads.” Yi personally saw no value in this glory-seeking practice and instructed his own men not to waste their time with it. “Rather than cutting off the heads of a few dead enemies,” he told them, “you are expected to shoot many of the living enemy. My eyes will judge who fights best.”[254] But the job seems to have suited Won Kyun very well. It gave him the battle honors he craved while keeping him out of the actual fighting, where he was apt to do more harm than good.

  Yi and Won arrived at Sachon later that same day to find more than four hundred enemy soldiers fortifying positions on the rocky hill above the port. Red and white banners had been raised in a line stretching three kilometers along the coast. A number of ships, all flying white ensigns, rode at anchor just offshore, including twelve large “pavilion vessels” with high castles built on their decks. Yi did not want to attack the ships where they lay. Such a close approach to shore would expose his force to enemy fire from the heights above and put his heavy ships at risk of running aground with the ebbi
ng tide. He preferred to deal with the enemy in open water, where there would be ample room to maneuver. Suspecting that the Japanese might feel overconfident at the sight of his mere twenty-three ships, Yi made a tentative entrance into the bay, then turned to retreat. Sure enough, more than half the Japanese on shore rushed to their ships to pursue the fleeing Koreans. Soon they were just where Yi wanted them, in the middle of the bay.

  And so the battle began. With the impregnable turtle ship captained by Na Tae-yong leading the way, the speedy Korean warships cut a swath through the lighter, slower, less maneuverable Japanese craft, ramming them, blasting away with cannon, setting them ablaze with fire arrows, and raining death upon their unprotected crews. The Japanese fought back as best they could, but their bullets and arrows were of little use against the heavy plank tops and sides of Yi’s board-roofed ships and turtle ship. Seeing his men begin to hesitate, Japanese commander Wakizaka Yasuharu is said to have leapt onto the gunwale of his flagship and cried, “These vessels the enemy are using are only like our mekura-bune (blind ships).[255] What is there to worry about? Board them and show what you are made of!” According to this Japanese account of the battle, Wakizaka and several of his retainers then managed to draw in one of the Korean warships with a grappling hook and scramble onto its roof, but were beaten back by withering counter-fire.[256]