Imjin War

In 1402, the Japanese shogun Ashikaga Yoshimitsu (despite not being the Emperor of Japan) was conferred the title of "King of Japan" by the Chinese emperor and through this title had similarly accepted a position in the imperial tributary system as of 1404. This relationship ended in 1408 when Japan, unlike Korea, chose to end its recognition of China's regional hegemony and cancel any further tribute missions. Membership in the tributary system was a prerequisite for any economic exchange with China. In exiting the system, Japan relinquished its trade relationship with China.

By the last decade of the 16th century, Toyotomi Hideyoshi, the most preeminent daimyō, had unified all of Japan in a brief period of peace. Since he came to hold power in the absence of a legitimate successor of the Minamoto lineage necessary for the imperial shōgun commission, he sought military power to legitimize his rule and to decrease his dependence on the imperial family. It is also suggested that Hideyoshi planned an invasion of China to fulfill the dreams of his late lord, Oda Nobunaga, and to mitigate the possible threat of civil disorder or rebellion posed by the large number of now-idle samurai and soldiers in unified Japan. It is also possible that Hideyoshi might have set a more realistic goal of subjugating the smaller neighbouring states (the Ryukyu Islands, Taiwan, and Korea) and treating the larger or more distant countries as trading partners, because throughout the invasion of Korea, Hideyoshi sought for legal tally trade with China.

By seeking to invade China, Hideyoshi was in effect claiming for Japan the role traditionally played by China in East Asia as the center of the East Asian international order. He rallied support in Japan as a man of relatively humble origins who owed his position to his military might. Finally, during the 1540s–1550s, the wakō had staged a series of samurai raids into Korea, some of which were so large as to be "mini-invasions". Hideyoshi mistakenly thought his enemies were weak.

The construction of as many as 2,000 ships may have begun as early as 1586. To estimate the strength of the Korean military, Hideyoshi sent an assault force of 26 ships to the southern coast of Korea in 1587. On the diplomatic front, Hideyoshi began to establish friendly relations with China long before he had completed the unification of Japan. He also helped to police the trade routes against the wokou.

In 1587, Hideyoshi sent his first envoy Yutani Yasuhiro, to Korea, which was during the rule of King Seonjo, to re-establish diplomatic relations between Korea and Japan (broken since the Wokou raid in 1555). Hideyoshi hoped to use as a foundation to induce the Korean court to join Japan in a war against Ming China. Around May 1589, Hideyoshi's second embassy reached Korea and secured the promise of a Korean embassy to Japan in exchange for a group of Korean rebels which had taken refuge in Japan.

In 1587, Hideyoshi had ordered an ultimatum to be sent to the Joseon Dynasty to submit to Japan and participate in the conquest of China, or face the prospect of open war with Japan. In April 1590, the Korean ambassadors asked for Hideyoshi to write a reply to the Korean king, for which they waited 20 days at the port of Sakai. Upon the ambassadors' return, the Joseon court held serious discussions concerning Japan's invitation. They nonetheless pressed that a war was imminent. Some, including King Seonjo, argued that Ming should be informed about the dealings with Japan, as failure to do so could make Ming suspect Korea's allegiance, but the court finally concluded to wait further until the appropriate course of action became definite.

In the end, Hideyoshi's diplomatic negotiations did not produce the desired result with Korea. The Joseon Court approached Japan as a country inferior to Korea, and saw itself as superior according to its favored position within the Chinese tributary system. It mistakenly evaluated Hideyoshi's threats of invasions to be no better than the common wokou Japanese pirate raids. The Korean court handed to Shigenobu and Genso, Hideyoshi's third embassy, King Seonjo's letter rebuking Hideyoshi for challenging the Chinese tributary system. Hideyoshi replied with another letter, but since it was not presented by a diplomat in person as expected by custom, the court ignored it. After this denial of his second request, Hideyoshi proceeded to launch his armies against Korea in 1592.

The Japanese invasion force consisting of 400 transports bearing 18,700 men under the command of Konishi Yukinaga departed from Tsushima Island on May 23 and arrived at Busan harbor without any incident. The Joseon fleet of 150 ships did nothing and sat idle at port. A single vessel bearing the daimyō of Tsushima, Sō Yoshitoshi (who had been a member of the Japanese mission to Korea in 1589), detached from the Japanese fleet with a letter to the commander of Busan, Yeong Bal, demanding that the Korean forces stand down to allow the Japanese armies to proceed on towards China. The letter went unanswered, and the Japanese commenced landing operations from four o'cklock the following morning.

While Sō Yoshitoshi attacked Busan, Konishi led a smaller force against the fort of Dadaejin, located a few kilometers to the southwest of Busan at the mouth of the Nantong River. Konishi Yukinaga's first attack was repelled by Yun Heungsin. The second attack came at night when Japanese forces filled the moat with rocks and lumber under cover of gunfire before scaling the walls using bamboo ladders. The entire garrison was massacred.

On the morning of May 25, 1592, the First Division arrived at Dongnae eupseong. Konishi sent a message to Song Sanghyǒn, the commander of the Dongnae fortress, explaining to him that his objective was the conquest of China and if the Koreans would just submit, their lives would be spared. Song replied "It is easy for me to die, but difficult to let you pass", which led Konishi to order that no prisoners be taken to punish Song for his defiance. The resulting Siege of Dongnae lasted twelve hours, killed 3,000, and resulted in Japanese victory.The Japanese took no prisoners and killed everyone at Dongnae, civilian and military, even killing all of the cats and dogs of Dongnae.

However, as with previous engagements, the superior range and firepower of the arquebus-armed ashigaru soldiers inflicted heavy casualties on the crowded Korean forces while remaining out of range of the defender's bows and spears. Sin Rip did manage one cavalry charge, but found that various vegetation on the plain impeded his horses and that the Japanese forces also employed a considerable number of pikemen, who were able to break his charge before he could penetrate the Japanese lines. Sin Rip and a number of his commanders mounted on horses managed to escape the disaster; however, most of his men were cut down by the Japanese as they attempted to retreat. Sin Rip later killed himself to atone for the defeat by drowning himself in a spring a short distance from Chungju.

Konishi arrived at Hanseong first on June 10 while the Second Division was halted at the river with no boats with which to cross. The First Division found the castle undefended with its gates tightly locked, as King Seonjo and the Royal Family had fled the day before. The Japanese broke into a small floodgate, located in the castle wall, and opened the capital city's gate from within. Katō's Second Division arrived at the capital the next day (having taken the same route as the First Division), and the Third and Fourth Divisions the day after. Parts of Hanseong had already been looted and torched, including bureaus holding the slave records and weapons, and they were already abandoned by its inhabitants. The King's subjects stole the animals in the royal stables and fled before him, leaving the King to rely on farm animals. In every village, the King's party was met by inhabitants, lined up by the road, grieving that their King was abandoning them, and neglecting their duty of paying homage.

Yi Sunsin's fleet of 39 warships depart from Yeosu.

At the outbreak of hostilities, Admiral Yi had sent out his fleet out on a naval exercise. Upon hearing that Pusan had been captured, Yi immediately set out on an east course to Pusan, hoping to block Japanese naval advances along the coast to aid their land forces.

His first encounter at Okpo was a decisive victory, destroying almost half of the ships of the anchored Japanese fleet of Todo Takatora. Prior to the Okpo Campaign, Yi mainly patrolled the seas near his Jeolla Province, to fortify its position before he began moving westward, due to the call for help from Admiral Won Gyun. A day later, after destroying an additional 18 Japanese transports in nearby waters (at Happo and Jeokjinpo), Yi Sun-sin and Won Gyun parted ways and returned to their home ports after receiving news of the fall of Hanseong.

However, Yi treated each battle with extreme care and made certain that he suffered few serious casualties. From his Okpo battle, the only casualty was a minor gunshot wound on an oarsman from stray musket fire. The Battle of Okpo caused anxiety and nervousness among the Japanese, because afterward Yi began to deploy his navy to attack Japanese supply and carrier vessels.

The Hamgyong campaign was largely due to the help of Korean defectors who also handed over to the Japanese their princes Sunhwa and Imhae. The Japanese reached the northeastern edge of Hamgyeong, crossed the Duman River, and attacked the Orangai Jurchens, but met with heavy resistance. Katō returned south and took up residence in Anbyeon while Nabeshima Naoshige headquartered in Gilju. By winter local resistance began pushing back at Japanese occupation and laid siege to Gilju.

From the beginning of the war, the Koreans organized militias that they called "righteous armies" (Korean: 의병) to resist the Japanese invasion. These fighting bands were raised throughout the country, and participated in battles, guerilla raids, sieges, and the transportation and construction of wartime necessities.

There were three main types of Korean "righteous army" militias during the war: the surviving and leaderless Korean regular soldiers, the patriotic yangbans (aristocrats) and commoners, and Buddhist monks. By the summer of 1592, there were about 22,200 Korean guerrillas serving the Righteous Army, who tied up much of the Japanese force.

During the first invasion, Jeolla Province remained the only untouched area on the Korean peninsula. In addition to the successful patrols of the sea by Yi Sun-sin, the activities of volunteer forces pressured the Japanese troops to avoid the province in favour of other priorities.

The Japanese vanguard was the army under Konishi Yukinaga and Sō Yoshitoshi, followed by the army of Kato Kiyomasa and the army of Kuroda Nagamasa. The Japanese forces arrived at the Imjin River without difficulty, but found that the Koreans had finally managed to mount an effective defense, and had 10,000 soldiers amassed on the far bank under the command of Gim Myeongweon. Seeing that the Koreans would not budge after waiting for ten days, the Japanese forces conducted a false retreat to lure them into attacking. The Koreans took the bait and one inexperienced commander Sin Hal immediately ordered his men to cross the river and attack the Japanese. A portion of the Korean army thus crossed the river and rushed past the abandoned Japanese campsite into the ambush. The Japanese fired on them with muskets and chased them to the river where they were slaughtered. The Japanese crossed the river by 7 July and took Kaesong without a fight. Afterwards the three divisions split up. Konishi Yukinaga went north to Pyeongyang, Kuroda Nagamasa went west to Hwanghae, and Katō Kiyomasa headed northeast to Hamgyeong.

Admiral Yi set out again eastward and encountered another force around the Sacheon-Dangpo area, where he again engaged in minor skirmishes against the Japanese fleet. Yi Sunsin's fleet managed to destroy 13 large Japanese ships. It was the first battle of Admiral Yi's 2nd Campaign in the Imjin War, between Japan and Korea, when the turtle ship was first used. The fierce and sudden Korean attack shocked the Japanese. But unlike their previous poor performance at the Battle of Okpo, the Japanese soldiers fought bravely and returned fire with their arquebuses in a timely manner.

Unfortunately for the Japanese, they did not have a chance to board the Korean ships because of concentrated Korean cannon fire. Also, the turtle ship was impossible to board anyway due to iron spikes on its roof. Then, the Japanese began to panic when the turtle ship smashed into Japanese lines, firing in every direction.

As the Korean fleet approached the Dangpo harbor, Yi Sun-shin noticed that the flagship of this Japanese fleet was anchored among the other vessels. Realizing the golden opportunity, Admiral Yi led the assault with his own flagship (a turtleship) targeting the Japanese flagship. The sturdy construction of his turteship allowed Yi Sun-shin to easily ram through the line of Japanese ships and position his ship right alongside the anchored Japanese flagship. The light construction of the Japanese ship was no match for a full broadside assault and was left sinking in minutes. From the turtle ship, a hail of cannonballs rained down on the other ships, destroying more vessels. The Koreans circled the other ships anchored and began to sink them. Then, Korean general Kwon Joon shot an arrow into Kurushima. The Japanese commander fell dead and a Korean captain jumped onboard and cut off his head. The Japanese soldiers panicked upon seeing the beheading of their admiral and were slaughtered by the Koreans in their confusion.

The Korean fleet assumed a circular formation to navigate the enclosed bay and took turns bombarding the Japanese. Realizing that this would only force the Japanese to flee inland, Yi Sunsin ordered a false retreat. Falling for the ploy, the Japanese fleet gave chase, only to be surrounded and shot to splinters. A few Japanese managed to flee to shore and take refuge in the hills. All the Japanese ships were destroyed. After securing this area (the last in the series of Jeolla coastal defenses), Admiral Yi decided to press the advantage of his enemy's inactivity and moved out to the Noryang-Hansando area. The Korean fleet spent the next few days searching for Japanese ships but could not find any.  On 18 July the fleet was dissolved and each commander returned to their respective ports.

Realizing that the Japanese attack was coming, Korean General Gim Myeongweon had his remaining men sink their cannon and arms into a pond to prevent them from falling into the hands of the Japanese, and fled north to Sunan. The Japanese crossed the river on 24 July and found the city completely deserted. Suspecting a trap, Konishi and Kuroda sent scouts to a nearby hill to confirm before entering the empty city. Within the city's warehouses, they found seven thousand tons of rice, which would be enough to feed their army for several months. The Japanese occupation of Pyeongyang would not be contested until Ming general Zhu Chengxun arrived with 6,000 men on 23 August 1592.

Desperate Korean envoys had been finally sent to the Forbidden City in Beijing to ask the Wanli Emperor to protect his loyal vassals in Korea by sending an army to drive out the Japanese. The Chinese assured the Koreans that an army would be sent, but they were engaged in a major war in Ningxia, and the Koreans would have to wait for the arrival of their assistance.

Toyotomi Hideyoshi made an order to Kobayakawa Takakage to attack the Jeolla Province. Jeolla Province was famous for it rice, and Japan needed that rice to feed their army. Also, Admiral Yi Sun-sin's naval force was stationed in Jeolla Province. Capturing Jeolla Province would provide a land route for the Japanese army to attack Admiral Yi, who had interfered with Japanese supply lines for the past two months. So Kobayakawa, who was in Seoul at the time, advanced to attack the Korean army.

Japanese army needed to go from Geumsan County to Jeonju to capture the province. There were two paths that the Japanese could take. One path was blocked by a hill called Ungchi and the other was blocked by Ichi hill. The Japanese split their forces and so did the Koreans. So the battle for Ichi and Ungchi happened at the same time. At the same time, Ko Kyong-myong was advancing to Geumsan to try to trap the Japanese. Although force at Ichi were winning by the 8th, Korean force at Ungchi routed to Jeonju at that time and the Japanese force advanced to Jeonju by that path. However, later on, Japanese force retreated from Ichi and Jeonju. Ko Kyong-myong force has arrived and was attacking the Japanese rear. The Koreans won this battle and stopped the Japanese army from advancing to Jeolla Province. As a result, Japan failed to provide enough rice for its army, which affected its ability to fight.

In response to the Korean navy's success, Toyotomi Hideyoshi recalled three commanders from land-based activities: Wakisaka Yasuharu, Katō Yoshiaki, and Kuki Yoshitaka. They were the first commanders with naval responsibilities in the entirety of the Japanese invasion forces. Hideyoshi understood that if the Koreans won command of the sea, this would be the end of the invasion of Korea, and ordered the destruction of the Korean fleet with Yi Sun Sin's head to be brought to him. Kuki, a former pirate, had the most naval experience, while Katō Yoshiaki was one of the "Seven Spears of Shizugatake". However, the commanders arrived in Busan nine days before Hideyoshi's order was actually issued, and assembled a squadron to counter the Korean navy. Eventually Wakisaka completed his preparations, and his eagerness to win military honor pushed him to launch an attack against the Koreans without waiting for the other commanders to finish.

The combined Korean navy of 53 ships under the commands of Yi Sun-sin and Yi Eok-gi was carrying out a search-and-destroy operation because the Japanese troops on land were advancing into the Jeolla Province. The Jeolla Province was the only Korean territory to be untouched by a major military action, and served as home for the three commanders and the only active Korean naval force. The Korean navy considered it best to destroy naval support for the Japanese to reduce the effectiveness of the enemy ground troops.

On August 13, 1592, the Korean fleet sailing from the Miruk Island at Dangpo received local intelligence that a large Japanese fleet was nearby. After surviving a storm, the Korean fleet had anchored off Dangpo, where a local man appeared on the beach with the news that the Japanese fleet had just entered the narrow strait of Gyeonnaeryang that divided Koje Island. The following morning, the Korean fleet spotted the Japanese fleet of 82 vessels anchored in the straits of Gyeonnaeryang. Due to the narrowness of the strait and the hazard posed by the underwater rocks, Yi Sun-sin sent six ships as bait to lure out 63 Japanese vessels into the wider sea; the Japanese fleet pursued. Once in the open water, the Japanese fleet was surrounded by the Korean fleet in a semicircular formation, called a "crane wing" by Yi Sun-sin. With at least three turtle ships (two of which were newly completed) spearheading the clash against the Japanese fleet, the Korean vessels fired volleys of cannonballs into the Japanese formation. The Korean ships then engaged in a free-for-all battle with the Japanese ships, maintaining enough distance to prevent the Japanese from boarding; Yi Sun-sin permitted melee combats only against severely damaged Japanese ships. During the battle, the Korean navy made use of a metal-cased fire bomb that caused substantial damage to Japanese deck crews, and caused fierce fires on board their ships.

The battle ended in a Korean victory, with Japanese losses of 59 ships – 47 destroyed and 12 captured. Not a single Korean ship was lost during the battle. Wakisaka Yasuharu escaped due to the speed of his flagship. After this, Yi set up his headquarters on Hansan Island itself and began plans to attack the main Japanese base at Pusan harbor.

News of the Japanese defeat at Hansan Island reached Busan within hours and two Japanese commanders, Kuki Yoshitaka and Kato Yoshiaki, immediately set sail with 42 ships for the port of Angolpo, where they hoped to face the Korean fleet close to shore.

Yi Sun-sin received news of their movements on 15 August and he advanced towards Angolpo to confront them. This time the Japanese were unwilling to follow the Koreans into open water and stayed onshore. They would not take the bait. In response the Korean fleet moved forwards and bombarded the anchored Japanese fleet for hours until they retreated inland. Later the Japanese returned and escaped on small boats. Both Kuki and Kato survived the battle.

The battles of Hansan Island and Angolpo forced Hideyoshi to give a direct order to his naval commanders to cease all unnecessary naval operations and limit activity to the immediate area around Pusan Harbor. He told his commanders that he would come to Korea personally to lead the naval forces himself, but Hideyoshi was never able to carry through on this as his health was deteriorating rapidly. This meant that all the fighting would be in Korea, not China, and that Pyongyang would be the furthest northwestern advance of the Japanese armies (to be sure, Katō Kiyomasa's second contingent's brief march into Manchuria was Japan's northernmost advance, however, Manchuria was not a part of Imperial China in the 16th century). While Hideyoshi was unlikely to be able to invade China and conquer a large part of it, the battles of Hansan Island and Angolpo checked his supply routes and hindered his movements in Korea.

Viewing the crisis in Joseon, the Ming Dynasty Wanli emperor and his court were initially filled with confusion and skepticism as to how their tributary could have been overrun so quickly.

The Korean Court was at first hesitant to call for help from the Ming Dynasty, and began a withdrawal to Pyongyang. After repeated requests by King Seonjo and after the Japanese army had already reached Korea's border with China, China finally came to the aid of Korea. China was also somewhat obligated to come to the assistance of Korea because Korea was a vassal state of China, and the Ming Dynasty did not tolerate the possibility of a Japanese invasion of China. The local governor at Liaodong eventually acted upon King Seonjo's request for aid following the capture of Pyongyang by sending a small force of 5,000 soldiers led by Zu Chengxun. Zu, a general who had fought successfully against the Mongols and the Jurchens, was over-confident, holding the Japanese in contempt.

The combined army of Zhu Chengxun and Shi Ru arrived at Pyeongyang on 23 August 1592 in a pouring rain at night. The Japanese were caught completely off guard and the Ming army was able to take the undefended Chilsongmun ("Seven Stars Gate") in the north wall and entered the city. However the Japanese soon realized just how tiny the Ming army actually was, so they spread out, causing the enemy army to stretch out and disperse. The Japanese then took advantage of the situation and counterattacked with gunfire. Small groups of isolated Ming soldiers were picked off until the signal to retreat was sounded. The Ming army had been turned around, driven out of the city, its stragglers cut down. By the end of the day, Shi Ru was killed while Zhu Chengxun escaped back to Uiju. Some 3,000 Ming soldiers were killed. Zhu Chengxun attempted to downplay the defeat, advising King Seonjo that he had only made a "tactical retreat" due to the weather, and would return from China after raising more troops. However, upon his return to Liaodong, he wrote an official report blaming the Koreans for the defeat. Ming envoys sent to Korea found this accusation groundless.

Katō Kiyomasa, leading the Second Division of more than 20,000 men, crossed the peninsula to Anbyon County with a ten-day march, and swept north along the eastern coast. Among the castles captured was Hamhung, the provincial capital of Hamgyong Province. There a part of the Second Division was assigned to defense and civil administration.

The rest of the division, 10,000 men, continued north, and fought a battle on August 23 against the southern and northern Hamgyong armies under the command of Yi Yong at Songjin. A Korean cavalry division took advantage of the open field at Songjin, and pushed the Japanese forces into a grain storehouse. There the Japanese barricaded themselves with bales of rice, and successfully repelled a charge from the Korean forces with their arquebuses. While the Koreans planned to renew the battle in the morning, Katō Kiyomasa ambushed them at night; the Second Division completely surrounded the Korean forces with the exception of an opening leading to a swamp. Those that fled were trapped and slaughtered in the swamp.

Koreans who fled gave alarm to the other garrisons, allowing the Japanese troops to easily capture Kilju County, Myongchon County, and Kyongsong County. The Second Division then turned inland through Puryong County toward Hoeryong, where two Korean princes had taken refuge. On August 30, 1592, the Second Division entered into Hoeryong where Katō Kiyomasa received the Korean princes and the provincial governor Yu Yong-rip, these having already been captured by the local inhabitants. Shortly afterward, a Korean warrior band handed over the head of an anonymous Korean general, plus General Han Kuk-ham, tied up in ropes.

Prompted by King Seonjo, the Buddhist monk Hyujeong issued a manifesto calling upon all monks to take up arms, writing "Alas, the way of heaven is no more. The destiny of the land is on the decline. In defiance of heaven and reason, the cruel foe had the temerity to cross the sea aboard a thousand ships". Hyujeong called the samurai "poisonous devils" who were "as virulent as snakes or fierce animals" whose brutality justified abandoning the pacifism of Buddhism to protect the weak and innocent. Hyujeong ended his appeal with a call for monks who were able-bodied to "put on the armor of mercy of Bodhisattvas, hold in hand the treasured sword to fell the devil, wield the lightning bolt of the Eight Deities and come forward!". At least 8,000 monks responded to Hyujeong's call, some out of a sense of Korean patriotism and others motivated by a desire to improve the status of Buddhism, which suffered discrimination from a Sinophile court intent upon promoting Confucianism.

Hyujeong and the monk Yeonggyu gathered a force of 2,600 to attack Cheongju, which served as the administrative center of central Korea and contained a large government granary. It was previously taken on 4 June and was under the control of Hachisuka Iemasa.

When the Koreans attacked, some of the Japanese were still out foraging for food. The Japanese came out and fired at the Koreans, but they were surrounded and killed. The Koreans didn't know how to use the matchlock firearms, so they used them as clubs. At this point a heavy downpour started so the Koreans fell back and retreated. The next day the Koreans discovered the Japanese had evacuated from Cheongju and took the city without a fight.

After the victory at the Battle of Cheongju, the Korean leaders began to quarrel among themselves over who was most responsible, and it was that when the Koreans took the offensive, the regulars under Yun Songak refused to take part while the Righteous Army under Hyujeong and the warrior monks under abbot Yeonggyu marched separately.

On 22 September 1592, Hyujeong with 700 Righteous Army guerrillas attacked a Japanese force of 10,000 under Kobayakawa Takakage. Turnbull described the second battle of Geumsan as an act of folly on Jo's part as his outnumbered force took on "10,000 of the toughest samurai", who encircled the Righteous Army and "exterminated" them, wiping out the entire Korean force as Kobayakawa ordered that no prisoners be taken. Feeling obligated to come to Jo's aid, the abbot Yeonggyu now led his warrior monks against Kobayakawa at the third battle of Geumsan, who likewise suffered the same fate – "total annihilation".

However, as the Geumsan salient had taken three successive Korean attacks in a row in a single month, the 6th Division under Kobayakawa was pulled back as Toyotomi Hideyoshi decided the salient was not worth the trouble to hold it, and to the suffering people of the region that was all that mattered. The Japanese withdrawal inspired further guerrilla attacks and one Righteous Army leader, Pak Chin, had an object hurled over the walls of the Japanese-held town of Gyeongju, which caused "the robbers", as Korean accounts always called the Japanese, to go examine it; the object turned out to be a bomb that killed 30 Japanese. Fearing his garrison was now under-strength, the Japanese commander ordered a retreat to the coastal wajo (castle) at Sosaengpo.

In October 1592, Katō Kiyomasa decided to attack a nearby Jurchen castle across the Tumen River in Manchuria to test his troops against the "barbarians", as the Koreans called the Jurchens. Kato's army of 8,000 was joined by 3,000 Koreans, at Hamgyong, because the Jurchens periodically raided across the border. Soon the combined force sacked the castle, and camped near the border; after the Koreans left for home, the Japanese troops suffered a retaliatory assault from the Jurchens. Katō Kiyomasa retreated with his forces to avoid heavy losses. Because of this invasion, rising Jurchen leader Nurhaci offered military assistance to the Joseon and Ming in the war. However, the offer was refused by both countries, particularly Joseon, saying that it would be disgraceful to accept assistance from the "Barbarians" to the north.

Off the coast of Busan, the united Joseon fleet realized that the Japanese navy had readied their ships for battle and the Japanese army had stationed themselves around the shoreline. The united Joseon fleet assembled in the Jangsajin, or "Long Snake" formation, with many ships advancing in a line, and attacked straight into the Japanese fleet. Overwhelmed by the Joseon fleet, the Japanese navy abandoned their ships and fled to the coast where their army was stationed. The Japanese army and navy joined their forces and attacked the Joseon fleet from the nearby hills in desperation. The Joseon fleet shot arrows from their ships to defend and restrict their attacks, and in the meantime concentrated their cannon fire on destroying Japanese vessels.The Korean ships fired on the Japanese fleet and burned them using fire arrows while the Japanese fired on them from above in their forts. Even with cannons captured at Busan, the Japanese did little damage to the Korean warships. By the time the day had ended, 128 Japanese ships had been destroyed. Yi Sunsin gave orders to withdraw, ending the battle.

Yi Sun Shin originally intended to destroy all the remaining Japanese ships, however, he realized that doing so would effectively trap the Japanese soldiers on the Korean Peninsula, where they would travel inland and slaughter the natives. Therefore, Yi left a small number of Japanese ships unharmed and withdrew his navy to resupply. And just as Yi suspected, under the cover of darkness, the remaining Japanese soldiers boarded their remaining ships and retreated.

After this battle, the Japanese forces lost the control of the sea. The devastating blow dealt to the Japanese fleet isolated their armies in Korea and cut them off from their home bases. Since the Japanese forces realized the importance of the defensive lines of Busan Bay to secure the supply line, they tried to bring the west area of Busan under their control, when the Joseon navy came.

The Japanese heartily approached Jinju fortress. They expected another easy victory at Jinju but the Korean general Kim Si-min defied the Japanese and stood firm with his 3,800 men. Again, the Koreans were outnumbered. Kim Si-min had recently acquired around 170 arquebuses, equivalent to what the Japanese used. Kim Si-min had them trained and believed he could defend Jinju. After three days of fighting, Kim Si-min was hit by a bullet on the side of his head and fell, unable to command his forces. The Japanese commanders then pressed even harder on the Koreans to dishearten them, but the Koreans fought on. The Japanese soldiers were still unable to scale the walls even with heavy fire from arquebuses. The Koreans were not in a good position since Kim Si-min was wounded and the garrison was now running low on ammunition. Gwak Jae-u, one of the main leaders of the Righteous armies of Korea arrived at night with an extremely small band, not enough to relieve the Koreans at Jinju. Gwak ordered his men to grab attention by blowing on horns and making noises. About 3,000 guerrillas and irregular forces arrived at the scene. At this time, the Japanese commanders realized their danger and were forced to abandon the siege and retreated.

The Ming Emperor mobilized and dispatched a larger force under the general Li Rusong and Imperial Superintendent Song Yingchang. According to the collection of letters left by Song Yingchang, the strength of the Ming army was around 40,000, composed mostly of garrisons from the north, including around 3,000 men with experience against Japanese pirates under Qi Jiguang. Li wanted a winter campaign as the frozen ground would allow his artillery train to move more easily than it would under the roads turned into mud by the fall rains. At Uiju, King Sonjo and the Korean court formally welcomed Li and the other Chinese generals to Korea, where strategy was discussed. On January 5, Wu Weizhong leads 5,000 men across the Yalu River. Li Rusong's army of 35,000 reaches the Yalu River a few weeks later.

A Ming force of 43,000 with 200+ cannons and a Joseon army of 10000 with 4200 monks siege Pyongyang held by the Japanese. In the morning of 8 January, Li Rusong's army advanced on the city, their tightly packed ranks "looking like the scales on a fish. The Japanese defense was almost too much. Although nominally successful in repelling the enemies, the Japanese were no longer capable of defending the city. All the gates had been breached, no food was left, and they had suffered horrible casualties. With this in mind Konishi led the entire garrison out into the night and snuck across the frozen Daedong River back to Hanseong. Konishi's men reached Hanseong on 17 February. Song Yingchang invited Seonjo of Joseon to return to Pyeongyang on 6 March.

The Battle of Byeokjegwan was a military engagement fought on 27 February 1593 between the armies of the Ming dynasty led by Li Rusong and Japanese forces under Kobayakawa Takakage. It resulted in Japanese victory and Ming retreat. The battle lasted from late morning until noon. Finally Li Rusong was forced to retreat in the face of superior numbers. The Japanese burned all the grass within the vicinity of Hanseong to deprive the Ming cavalry of fodder.

The Japanese attack led by Konishi Yukinaga with 30,000 men. They took turns attacking the stockade due to the limited space. The Koreans retaliated with arrows, cannons, and hwacha. After three attacks, one with siege tower, and one where Ishida Mitsunari was wounded, Ukita Hideie managed to breach the outer defenses and reach the inner wall. When the Koreans had nearly run out of arrows, I Bun arrived with supply ships containing 10,000 more arrows, and they continued to fight on until dusk when the Japanese retreated. Aside from the defeat, the Japanese situation became even more tenuous after Zha Dashou led a small group of raiders to Hanseong, burning more than 6,500 tons of grain. This left the Japanese with less than a month of provisions.

After the Battle of Byeokjegwan, the Ming army took a cautious approach and moved on Hanseong again later in February after the successful Korean defense in the Battle of Haengju.

The two sides remained at a stalemate between the Kaesong to Hanseong line for the next couple of months, with both sides unable and unwilling to commit to further offensives. The Japanese lacked sufficient supplies to move north, and the defeat at Pyongyang had caused part of the Japanese leadership such as Konishi Yukinaga and Ishida Mitsunari to seriously consider negotiating with the Ming dynasty forces. This got them into a heated debate with other hawkish generals such as Katō Kiyomasa, and these conflicts would eventually have further implications following the war in Japan when the two sides became rivals in the Battle of Sekigahara.

The Ming forces had their own set of problems. Soon after arriving in Korea the Ming officials began to note the inadequate logistical supply from the Korean court. The records by Qian Shizhen noted that even after the Siege of Pyongyang the Ming forces were already stalled for nearly a week due to the lack of supplies, before moving on to Kaesong. As the time went on the situation only become more serious. When the weather warmed, the road condition in Korea also became terrible, as numerous letters from Song Yingchang and other Ming officers attest, which made resupplying from China itself also a tedious process.

The Korean countryside was already devastated from the invasion when the Ming forces arrived, and in the heart of winter it was extremely difficult for the Koreans to muster sufficient supplies. Even though the court had assigned the majority of the men on hand to tackle the situation, their desire to reclaim their country, along with the militarily inexperienced nature of many of their administrators, resulted in their continual requests to the Ming forces to advance despite the situation. These events created an increasing level of distrust between the two sides.

Though by mid April 1593, faced with ever-greater logistical pressure from a Korean naval blockade of Yi Sun-sin in addition to a Ming force special operation that managed to burn down a very significant portion of the Japanese grain storage, the Japanese broke off talks and pulled out of Hanseong.

The Japanese began on 20 July 1593. First they destroyed the edges of the dikes surrounding Jinju to drain the moat, then they advanced on the fortress with bamboo shields. The Koreans fired on them and repelled the attack. On 22 July the Japanese tried again with siege towers, but they were destroyed by cannon fire. On 24 July the Japanese were able to successfully mine a section of the outer wall under mobile shelters. On 27 July The Japanese now attacked with armored carts called "tortoise shell wagons", which allowed the Japanese to advance up to the walls, where the sappers would pull out the stones and attacked the weakened area of the wall, and with the aid of a rainstorm, were able to dislodge its foundations. The fortress was quickly taken. Like after most Japanese victories in largely populated areas, there was a massacre. The Japanese then retreated to Busan.

There were two factors that triggered the Japanese to withdraw: first, a Chinese commando penetrated Hanseong (present-day Seoul) and burned storehouses at Yongsan, destroying most of what was left of the Japanese troops' depleted stock of food. Secondly, Shen Weijing made another appearance to conduct negotiations, and threatened the Japanese with an attack by 400,000 Chinese. The Japanese under Konishi Yukinaga and Katō Kiyomasa, aware of their weak situation, agreed to withdraw to the Busan area while the Chinese would withdraw back to China. A ceasefire was imposed, and a Ming emissary was sent to Japan to discuss peace terms. For the next three years, there was little fighting as the Japanese retained control of a few coastal fortresses with the rest of Korea being controlled by the Koreans.

By May 18, 1594, all the Japanese soldiers had retreated to the area around Busan and many began to make their way back to Japan. The Ming government withdrew most of its expeditionary force, but kept 16,000 men on the Korean peninsula to guard the truce.

After the failed peace negotiations of the inter-war years, Hideyoshi launched the second invasion of Korea. One of the main strategic differences between the first and second invasions was that conquering China was no longer an explicit goal for the Japanese. Failing to gain a foothold during Katō Kiyomasa's Chinese campaign and the near complete withdrawal of the Japanese forces during the first invasion had established that the Korean peninsula was the more prudent and realistic objective.

Soon after the Ming ambassadors had safely returned to China in 1597, Hideyoshi sent approximately 200 ships with an estimated 141,100 men under the overall command of Kobayakawa Hideaki. Japan's second force arrived unopposed on the southern coast of Gyeongsang Province in 1596.

In addition, upon hearing the news in China, the Ming court in Beijing appointed Yang Hao as the supreme commander of an initial mobilization of 55,000 troops from various (and sometimes remote) provinces across China, such as Sichuan, Zhejiang, Huguang, Fujian, and Guangdong. A naval force of 21,000 was included in the effort. Ray Huang, a Chinese-American philosopher and historian, estimated that the combined strength of the Chinese army and navy at the height of the second campaign was around 75,000.

Prior to the battle, the previous naval commander Yi Sun-sin, had been removed from his post. The less experienced Won Gyun was promoted in Yi's place. Won Gyun set sail for Busan on 17 August with the entire fleet, some 200 ships.

The Korean fleet arrived near Busan on 20 August in 1597. As the day was about to end, they met a force of 500 to 1,000 Japanese ships arrayed against them. Won Gyun ordered a general attack on the enemy armada, but the Japanese fell back, letting the Koreans pursue. After a few back and forth exchanges, with one chasing the other, one retreating, the Japanese turned around one last time, destroying 30 ships and scattering the Korean fleet. His ships were overwhelmed by arquebus fire and the traditional Japanese boarding attacks, which largely resulted in the destruction of his entire fleet. Bae Seol shifted 12 ships to an inlet farther down the strait and managed to escape.

Ukita Hideie arrive on Namwon with around 49,600 soldiers. On 24 September, the Japanese filled the trench with straw and earth. Then they took shelter in the burned out houses in the city. On 25 September, the Japanese asked the defenders to surrender, but they refused. On the night of 26 September, the Japanese bombarded Namweon for two hours while their men climbed the walls and used fresh straw to create a ramp to the top. Unable to burn the moist rice stalks, the defenders were helpless against the Japanese onslaught and the fortress fell.

Hwangseoksan Fortress consisted of extensive walls that circumscribed the Hwangseok Mountains and garrisoned thousands of soldiers led by generals Jo Jong-do and Gwak Jun. When Katō Kiyomasa laid siege to the mountain with the Army of the Right, which he attacked at night under the full moon, the Koreans lost morale and retreated with 350 casualties. The successful siege did not, however, lead to a subsequent advance from beyond Gyeongsang Province.

On 16 October 1597, Kuroda Nagamasa's force of 5,000 arrived at Jiksan, where 6,000 Ming soldiers were stationed. Kuroda's forces charged the enemies and was soon joined by the rest of the army, bringing Japanese forces to 30,000. Although heavily outnumbering the Ming, the Japanese were unable to do much damage due to the Ming's superior armor. According to Kuroda and Mōri Hidemoto, their firearms could not penetrate the iron shields used by Chinese soldiers, and their armor was at least partially bulletproof. The battle continued until dusk when the two sides withdrew. Jiksan was the furthest the Japanese ever got towards reaching Hanseong during the second invasion. Although they were forced to withdraw at Jiksan, it was not a major loss, and resulted in an orderly retreat south by the Japanese.

With only 13 ships remaining from Admiral Won Gyun's disastrous defeat at the Battle of Chilchonryang, Admiral Yi held the strait as a "last stand" battle against the Japanese navy, who were sailing to support their land army's advance towards the Joseon capital of Hanyang (modern-day Seoul). The dense formation of Japanese ships crowded in the narrow strait made a perfect target for Joseon cannon fire. By the end of the battle, approximately 30 Japanese warships were sunk. The immediate results of the battle were a shock to the Japanese command. Joseon and Ming armies were able to regroup.

Yang Hao, Ma Gui, and Gwon Yul met up at Gyeongju on the 26 January 1598 and marched on Ulsan with an army of 50,000.

The battle began with a false retreat that lured the Japanese garrison into a frontal attack. They were defeated with 500 losses and were forced to retreat to Tosan fortress. The allies occupied the city of Ulsan.

On 30 January the allies bombarded the fortress and then took the outer wall of Tosan. The Japanese abandoned much of their food supplies and retreated into the inner fortress. The allies assaulted the inner fortress, at one point even taking a portion of the wall, but suffered heavy casualties.

On 19 February the allied forces attacked again and were repelled. Seeing Japanese reinforcements arrive, Yang Hao decided to lift the siege and retreat, but the disorganized movement led to many stragglers being cut down by the Japanese, leading to heavy casualties.

The Council of Five Elders, in late October, issued orders for the withdrawal of all forces from Korea. Hideyoshi's death was kept a secret by the Council to preserve the morale of the army.

The Chinese believed that Sacheon was crucial to their goal of retaking the lost castles in Korea and ordered a general attack. Although the Chinese made initial progress, the tide of battle turned when Japanese reinforcements attacked the rear of the Chinese army and the Japanese soldiers inside the fortress sallied from the gates and counter-attacked. The Chinese Ming forces retreated with 30,000 losses, with the Japanese in pursuit. According to Chinese and Korean sources concerning the battle, the forces led by Dong Yi Yuan had breached the castle wall and were making progress in capturing the castle until a gunpowder accident caused an explosion in their camp, and the Japanese took advantage of the situation to rout the confused and weakened troops.

The Battle of Noryang, the last major battle of the Japanese invasions of Korea (1592–1598), was fought between the Japanese navy and the combined fleets of the Joseon Kingdom and the Ming dynasty.

The allied force of about 150 Joseon and Ming Chinese ships, led by admirals Yi Sun-sin and Chen Lin, attacked and either destroyed or captured more than half of the 500 Japanese ships commanded by Shimazu Yoshihiro, who was attempting to link-up with Konishi Yukinaga. The battered survivors of Shimazu's fleet limped back to Pusan and a few days later, left for Japan. At the height of the battle, Yi was hit by a bullet from an arquebus and died shortly thereafter.

The war left significant legacies in all three countries. In the context of Japanese imperialism, the invasions are seen as the first Japanese attempt to become a global power. The partial occupation of Korea developed the Japanese concept that Korea belonged within Japan's sphere of influence, and the Japanese leaders of the late 19th and the early 20th centuries used the 1592–1597 invasions to reinforce the justification for their 20th century annexation of Korea. Yi-Sun Sin's accomplishments in the war also inspired Japanese naval officers during the 19th and 20th century, with many of them citing the importance of studying his battle tactics to further strengthen their navy.

In China, the war was used politically to inspire nationalistic resistance against Japanese imperialism during the 20th century. In Chinese academia, historians list the war as one of the Wanli Emperor's "Three Great Punitive Campaigns". Contemporary Chinese historians often use the campaigns as an example of the friendship that China and Korea shared.

In Korea, the war is a historic foundation of Korean nationalism and, as in China, inspired and politically used to instigate nationalistic resistance against Japanese imperialism during the 20th century. Korea gained several national heroes during the conflict, including Yi Sun-sin and Chen Lin (founder of the Gwangdong Jin clan). Modern anti-Japanese sentiment in Korea can be traced as far back as the Japanese invasions in 1592, although the principal cause is rooted in more recent events, particularly the hardships suffered by Koreans during the Japanese occupation of Korea from 1910 through 1945.