Ch 12 - Japanese Invasions

The Imjin War

Hideyoshi's army invaded Choson with overwhelming force in 1592. The army occupied Seoul within three weeks and took Pyongyang soon after. The legendary exploits of Admiral Yi Sun-sin killed any hope that Japan would ever succeed in invading China or hold on to its position in Choson.

Born in Seoul on April 28, 1545, Yi Sun-sin thoroughly absorbed the tactics and theories of the Seven Military Classics and passed his military examination in 1576. He not only studied the ancient military and literary classics, but actually understood how to apply their principles to contemporary warfare. This gifted naval architect with an unusual talent for mechanical inventiveness became a true soldier-scholar and a great military leader. His broad grasp of the strategic situation facing Choson from Japan and his remarkable, proven skills as a naval tactician rightfully place Admiral Yi Sun-sin among the world's great military commanders, heroic men like England's Admiral Horatio Nelson, and America's generals Robert E. Lee, George S. Patton, and Douglas A. MacArthur .

Typical fighting ships in sixteenth century Choson and Japan were little different than their merchant ship counterparts. Fighting ships generally had more oars for greater speed and a better hull design for added maneuverability. Japanese fighting ships still used the boarding tactics employed in the Battle of Lepanto. The captains's main goal was to get close enough to the enemy ship to use grappling hooks and pull his ship close aboard so his soldiers could then engage in hand-to-hand combat with the enemy. When that wasn't possible, archers and men armed with matchlock rifles targeted the crew of the enemy ship and frequently fired flaming arrows to set the enemy ship ablaze. Even the arquebus, a predecessor to the musket used by the Japanese, required the ships to get close enough for the guns to be effective. Well aware of his navy's current limitations, potential threats, and the need to improve and strengthen Choson's naval forces, Admiral Yi Sun-sin began work in 1588 to develop an entirely new ship design.

While diplomatic wrangling continued between Seoul and Kyoto, Admiral Yi was busy creating a genuinely secret weapon, the kobukson, or "turtle ship." Although Yi Sun-sin is commonly given credit for inventing the "turtle ship," the term kobukson was actually used in historic documents as early as 1414, when King T'aejong first inspected this new warship design. The aggressive use of the kobukson in Koryo's 1419 raid against pirates on Tsushima Island certainly indicates it was originally designed as an attack ship.

Beginning with a hull design adapted for high speed and maneuverability, Admiral Yi's highly-modified kobukson was essentially a flat-bottomed, oar-powered galley 100 feet in length with a 25 foot beam and two large masts rigged with large rectangular sails. Admiral Yi did not have to defend the open seas of the Tsushima Strait, but faced the constant battlefield constraint of inadequate maneuvering room in the narrow channels and shallow waters among the 400 small islands and uninhabited islets of the Hallyo Waterway. This small inland sea stretches 172 km from Hansan Island in the east, including Chungmu, SamChonp'o and Namhae Island, Odong Island, to the seaport of Yosu in the west.

Japanese superiority in both soldiers and firearms made engaging Japanese ships at close quarters a very dangerous tactic. Admiral Yi could not afford to be boarded, so he designed an arched "roof," believed to have been made of iron plate, that covered ship's entire topside structure to ward off enemy arrows and cannon shells. The top of this roof was studded with sharp upright spikes to deter potential boarders. The Yi court had discussed the idea of building ironclad ships as early as 1413, but the world's first ironclad warship was not actually built until Yi Sun-sin took command of the Choson navy.

Choson had already manufactured some very powerful cannons designed to protect fortresses and they soon figured out how to put them on ships. Yi Sun-sin increased the firepower of his kobukson by mounting thirteen small cannon atop the rowing deck along both flanks of the ship that fired through portholes to allow the vessel to deliver a broadside attack from either side at will. The Choson Navy had four types of cannons;  Chon (heaven), chi (earth), hyon (black) and hwang (yellow). The heavy 660 pound Chon cannon, with a 5.5 inch bore, could hurl a cannonball only a few hundred yards. Smaller and shorter in range than contemporary English cannons, Admiral Yi's guns certainly proved adequate to counter the threat posed by the smaller cannons aboard Japanese ships.

A large dragon head sat above the reinforced ram in the ship's bow and a wood-fired smoke generator was used to spew sulfur smoke through the dragon's grinning mouth. When put to use with the ship underway, the smoke screen enshrouded the entire ship and no doubt intimidated superstitious enemy sailors. The addition of new advanced cannons, archery ports ahead, astern and abeam, iron spikes on the roof, and the smoke generator in the bow made the kobukson a true offensive weapon.

The primary strength of Choson's professional military resided in its naval forces garrisoned along the southern coast, the direct result of Japanese pirate activity in Korea during the fourteenth century. In 1591, faced with an imposing threat from Japan and with Choson's very existence at stake, Chief Minister Yu Songnyong persuaded the royal court to appoint Admiral Yi Sun-sin to the post of Naval Commander of the Left (western) Cholla Province Naval Station headquartered at the southeastern port city of Yosu. There, in early 1592, Admiral Yi energetically set about training crews for his new warships.

With Choson enmeshed in factional squabbling, Hideyoshi readied his forces to move into Choson. From his headquarters in Hizen, Toyotomi Hideyoshi mobilized seven fully-equipped divisions, nearly 150,000 men and gathered a fleet of some 700 ships, transport vessels, naval ships and small craft to move his army across the Tsushima Strait. Many of the approximately 9,000 seamen who manned the Hideyoshi's fleet were reportedly former pirates. From their advanced staging area on Tsushima Island, an expeditionary force of three divisions (51,000 men) sailed for the south Choson coast near the end of May 1592:  11,000 men under General Kuroda Nagamasa, 18,000 men under the leadership of General Konishi Yukinaga, a Christian born of a merchant family from Sakai, and 22,000 men commanded by General Kato Kiyomasa, a Buddhist "mustang" officer who rose from the ranks with Hideyoshi.

Pusan garrison troops under the command of Chong Pal manned beachhead defensive positions around Pusan. To the north, a few miles inland at the small town of Tongnae, town magistrate Song Sang-hyon commanded a small civil defense force. General Konishi reached the port of Pusan a full five days ahead of generals Kato and Kuroda.The Japanese surprised and quickly overwhelmed the badly outnumbered defenders in both Pusan and Tongnae. Despite bravely defending the beachhead areas to the death, Choson's garrison troops proved no match for Japanese soldiers armed with short-range brass cannon and matchlock muskets. Moreover, they faced an army with extensive combat experience, men already bloodied from the many campaigns of Japan's Warring States period.

General Konishi had already established a beachhead in Choson by the time Kato and Kuroda's two remaining divisions reached Pusan. The combined Japanese army was too large to advance along a single route, particularly since the troops would have to live off the land. The Japanese left Pusan in three separate columns, opening a three-pronged northward assault toward the capital in Seoul. By messenger and beacon fires, reports of the invasion quickly reached the Yi court in Seoul along with reports of the many towns captured by the Japanese. Stunned by the news, King Sonjo's government panicked. The Border Defense Command quickly issued orders to call up the scattered remnants of the Choson army.

The government placed its hopes on the talents of General Sin Ip, a tough military fighter who had won earlier fame in successful campaigns against the Jurchen in the northern provinces. General Sin received orders to take all the men he could muster and contain the Japanese in the Naktong River basin by blocking the three mountain passes leading out of Kyongsang Province. Sin mustered a few thousand untrained men armed only with spears, bows and arrows. The leadership of this ragged group was even worse than the condition of the troops. Well before his small force reached the first of the mountain passes, General Sin received disturbing, detailed reports describing the Japanese army's battle prowess. Instead of taking the high ground, where tens of men could defend against thousands, the doughty general decided to wait for the advancing Japanese behind a strong defensive position established on an open plain near the city of Chungju, where he felt his men would fight better than in the mountains.

General Kuroda's division swept westward through the Sobaek Range over the Chup'ungyong Pass and proceeded north through the western provinces toward Seoul. General Konishi's division moved virtually unopposed up the center of Kyongsang Province. Meanwhile, General Kato's division, the third prong of the Japanese assault, drove north from Pusan toward Kyongju, turned northwestward, then linked up with Konishi in the valley near Chungju. After crossing the undefended Oryong Pass, Konishi's soldiers moved into the lower Han River valley, where the Japanese met their first strong resistance from General Sin Ip's rag-tag army. In the bitter and bloody fight that ensued, Japanese troops overran the Chungju defenders and killed General Sin.

The two Japanese divisions continued their march toward Seoul along two different routes. The main objective of the assault on Korea was plunder. The Japanese deployed six special units with orders to steal books, maps, paintings, craftsmen (especially potters) and their handicrafts, people to be enslaved, precious metals, national treasures, and domestic animals. Meeting little resistance, the Japanese ravaged the civilian population. Entire villages were swept up in the raids. Japanese merchants sold some of their loot to Portuguese merchants anchored offshore and took the rest to Japan.

If the summer of 1592 exposed fatal weaknesses in the Choson army with brutal thoroughness, it also highlighted the Choson navy's reputation. Admiral Yi Sun-sin proudly launched his kobukson just days before General Konishi's troops landed at Pusan in May 1592. The admiral selected eight of his most courageous naval officers to act as commandants at various ports. He also called up four government officials from their posts as magistrates of local cities and put them in the forefront of his battle formations as commanders of the Left Wing, Front Forward, Central Forward, and Right Forward commands. Within days of the outbreak of the Imjin War, Admiral Yi Sun-sin sailed into the Hallyo Waterway in search of Japanese shipping intent on engaging and destroying it whenever and wherever it might appear.

The war was less than ten days old when the Choson Navy had its first major engagement against the Japanese. Sailing from the southwest early one morning, Admiral Yi sighted the supply and troop ships that landed two Japanese divisions near Pusan less than two weeks earlier lying at anchor near Okp'o, off Koje Island. Borrowing a maxim from Sun Tzu's Art of War - "If the soldiers are committed to fight to the death they will live, whereas if they seek to stay alive they will die." - Admiral Yi gathered his captains and repeatedly had them pledge their willingness to fight.

Driven by a strong steady wind, Admiral Yi's ship led his ships downwind into the anchorage, firing cannon and arrows from both sides. Skillful maneuvering prevented the Japanese from boarding any of the attacking ships, which soon set a number of Japanese ships ablaze with flaming arrows. In the confusion that followed, Japanese sailors began cutting their anchor lines in a desperate attempt to flee. Few were lucky enough to escape destruction. In its first engagement the Choson Navy sank twenty-six Japanese vessels without a single loss. The only casualty was a sharpshooter who received a slight arm wound. It was the first naval combat action for many of the men in Admiral Yi's command, including many of the local magistrates recruited for military duty.

Sailing eastward from Okp'o under a steady wind, Admiral Yi ran across and attacked a smaller Japanese patrol squadron later that same afternoon. After annihilating the Japanese to the last ship before dark, he continued eastward for the rest of the night. The following morning, Admiral Yi's ships reached the main shipping lanes between Pusan and Tsushima Island, where he spotted a massive Japanese fleet sailing north. Undeterred by the odds, Admiral Yi plowed into the Japanese like a sledge-hammer. During the day-long battle, the Japanese fought with determined courage, but to no avail. By sundown, the entire Japanese fleet was either captured, ablaze, or on the bottom of the sea.

After a week of nearly constant action at sea, Admiral Yi wanted to attack Japanese ships at Pusan Harbor. After considering his situation however, with provisions low and his men exhausted and wounded, he wisely decided to avoid overextending his fleet deep into enemy territory and exposing himself to being cut off. With complete dominance of the seas along Choson's south coast and with no fear of a rival, Admiral Yi moved his fleet unobserved further west to the islands off the southern coast.

The relentless Japanese advance toward Seoul caused turmoil among the local population already gripped by confusion, fear and panic. Thoroughly alarmed and near panic themselves, King Sonjo and his court decided to flee north from Seoul to Kaesong. The government made no attempt to defend Seoul, but Sonjo ordered his two sons into the northern provinces of Hamgyong and Kangwon to raise fresh troops for the army. Neither of Sonjo's sons found anyone who would respond to their pleas to help defend the country against the Japanese. In the end, the Japanese captured both Choson princes.

King Sonjo made hasty preparations to abandon the city to the advancing Japanese. He gathered his family and with his retinue of high court officers fled through the west gate of the city along the "Beijing Road." When word of the impending royal evacuation reached the streets of the capital, citizens blocked their exit, hurling insults and stones at them. After fleeing the city to the north, the band of less than courageous aristocrats arrived in Kaesong only to be met again by local citizens armed with anger and masonry. Seven days later, the royal retreat finally crossed the Taedong River and halted in Pyongyang.

Infuriated by the government's incompetence and irresponsibility, the people of Seoul erupted in a furious rage. They placed the full blame for Choson's wretched state of affairs squarely on the backs of government officials, men who had failed to concern themselves with the welfare of the people and had permitted the farming villages to fall to ruin. Mobs of people swept through the city looting and burning government storehouses. The city's slave population attacked and burned the offices of the Ministry of Punishments and the hated Ministry of Justice. In their fury, mobs of angry citizens destroyed large numbers of census registers and the archives which held the slave-deeds. The destruction of the census registers and numerous other documents that recorded the status of Choson citizens by the Japanese freed many slaves from their bondage.

Less than three weeks after departing Tsushima Island, Konishi Yukinaga's division triumphantly marched through the South Gate into the city of Seoul. By late spring, all three of Hideyoshi's vanguard divisions occupied the Choson capital. Hideyoshi landed the remainder of his army on the nearly defenseless southern coast to occupy Kyongsang Province. There the Japanese quickly began to organize feudal land holdings similar to those in Japan for distribution to victorious commanders.

After leaving a garrison force to maintain order in the city of Seoul, the three vanguard divisions marched north. Konishi and Kato proceeded northwest toward Pyongyang, where they would halt and await resupply by the Taedong River. In their drive toward the ancient "western capital" of Koguryo, the Japanese encountered a determined defense force at the Imjin River. Choson defenders put up a fierce battle for three full days before the Japanese finally overran their positions. During the brief respite, King Sonjo and his entourage again took flight to the north, this time to the border city of Uiju on the Yalu River. General Kuroda turned his troops westward toward the Yellow Sea. General Kato marched eastward to subjugate the northern provinces of Hamgyong and P'yong'an, eventually crossing the Tumen River into Manchuria. General Konishi's division assaulted and captured Pyongyang. With no hope of repelling the Japanese alone, the royal court in hiding at Uiju dispatched envoys to Beijing with an urgent plea for help from Ming China.

In the south, Admiral Yi Sun-sin's second major campaign against the Japanese began off SaChon, where about four hundred Japanese soldiers were building fortifications to protect twelve pavilion vessels anchored near the wharf below. The Japanese held the high ground, safe among the cliffs facing the bay above SaChon, well beyond the reach of arrows. Since the ebbing tide made it impossible for Admiral Yi's kobukson to get within shooting range of Japanese ships, he employed a classic maneuver frequently cited in Sun Tzu's Art of War. Breaking his formations and giving every impression of a disorderly retreat, the well-disciplined Choson navy drew the Japanese into open water. Suddenly, Admiral Yi turned on his enemy and, as if riding a charging war chariot, drove right through their midst, firing cannon and flaming arrows into the Japanese ships. The ensuing battle turned into a complete rout as the Japanese broke and ran into the surrounding hills. Admiral Yi wisely spared a few Japanese ships to give the defeated soldiers a way to escape and to prevent them from terrorizing the local population.

Hideyoshi had the temperament of a land warrior and tended to think of his fleet as little more than transportation for the army. As a result, the Japanese "navy" embarked on the Choson invasion ill-armed and ill-trained for fighting at sea. Yi Sun-sin took full advantage of the mismatch. In several sea battles near Tangp'o and Tanghangp'o during June and July, he cleared the seas of poorly led Japanese ships using line-ahead tactics with rams and flaming arrows. In one battle, Yi Sun-sin caught a convoy with twenty-five escort ships bound for Pyongyang in open water and sent it to the bottom. Flushed with success, Yi Sun-sin's fleet lingered in the area the peninsula expecting further action.

A few days later, off Tanghangp'o, Admiral Yi once again sought the advantage of fighting in open water. He broke off his attack in a feigned retreat so the Japanese would not abandon their ships and escape to land. The results were the same as at SaChon. The Japanese set off in pursuit of the admiral's ships, which then counterattacked from both flanks and destroyed all but one of the Japanese ships. As planned, the next morning one of Admiral Yi's captains caught the lone escaping Japanese ship in open water and sank it.

Whether Hideyoshi knew of Admiral Yi Sun-sin's stunning naval successes or not, he committed a fatal blunder by holding to his original plan for reinforcing his land army in northern Choson through the western passage. The Japanese advance to Pyongyang had been so rapid that reserves meant to link up with them had to be embarked aboard ships by the end of June. In early July, hundreds of Japanese transport ships escorted by the majority of Hideyoshi's remaining fighting ships, set sail along the western passage toward the islands off Choson's southern coast and sailed directly into a trap. Anticipating the Japanese would sail a course to sight Choson's southern islands, Admiral Yi Sun-sin stationed his ships near Hansan Island and lay in wait for any Japanese shipping that happened by.

Anchored near the mouth of the Hansan Strait, a 400 yard-wide channel strewn with submerged rocks and shoals, Admiral Yi's ships were sitting in a position from which they could quickly sail in either direction. At dawn on the morning of July 9, 1592, lookouts sighted a Japanese fleet on the far eastern horizon. Fearing his large kobukson would be unable to maneuver effectively inside the strait, he decided to lure the Japanese into open water south of Hansan Island, where he could take the Japanese in a single strike.

The Battle of Hansan Island began when Admiral Yi moved five or six kobukson in a tentative attack against the approaching Japanese. When he was sure he had been sighted, he turned his ships and feigned a retreat under oars. The Japanese admiral, intent on capturing a fleeing enemy, gave immediate chase under full sail. Admiral Yi carefully drew the faster Japanese fighting ships further into open water, outrunning the slower transports. At the critical moment, and with his own ships still under oars, Admiral Yi suddenly turned about. In a spectacular demonstration of precisely-timed maneuvering, he fell hard against the lead Japanese ships, ramming them as they tried to turn away from the approaching attack. One by one, the lead Japanese ships crumbled against the reinforced bows of the kobukson and near continuous cannon fire. Those lucky enough to escape the initial disaster were driven back into the approaching main body of the convoy, which also turned away in panic to escape.

During the running fight, Admiral Yi's fleet sunk or set fire to some seventy Japanese fighting ships. When a large reinforcing convoy was spotted sailing into the onrushing melee, Japanese admirals made a valiant attempt to halt the retreat with the new arrivals. The two large bodies of ships closed on each other quickly, which added to the building confusion. Nearly fifty more Japanese ships were lost to ramming, cannon fire or flaming arrows. Faced with an apparently unconquerable enemy, for the first and only time while engaged with a foreign enemy, Japanese commanders lost courage, panicked and broke in all directions looking for a way out. The retreat quickly degenerated into a rout, with a mixture of transports, escorts and fighting ships sinking and burning together. The panic was so thorough that the majority of those who managed to escape made for the coast rather than suffer the fates of their comrades. Many ships were driven aground and wrecked with a great loss of life.

The Battle of Hansan Island not only annihilated the Japanese fleet, it destroyed the vital materiel needed by generals Konishi and Kato in the north. Admiral Yi Sun-sin's systematic application of the principles of Sun Tzu and other Chinese military classics in his four sweeping naval campaigns of 1592, culminated in a single battle which cut off the sea lanes around the southwestern tip of Choson and abruptly ended all prospects of a future Japanese invasion of China.