Chapter 1 Summary: In 1582, Nobunaga thwarted an attempted assassination attempt. In the following campaigns, he effectively unified Japan by 1589. With Japan unified, Nobunaga turned to inward reforms, such as promotion of Europeanization, as well as external expansion at the expense of China. This external expansion resulted in the declaration of war against Korea in 1591.
Chapter 2: High Noon
Despite Japan having declared war on them in 1591, Korea was not worried. Their southern coast had long been attacked by wako, Japanese pirates, which had lead to certain military evolutions. Because of the success these evolutions had against the wako, Korea was confident they could handle a Japanese invasion.
On land, the Koreans primary doctrine depended on the defensive. The linchpins of this defensive strategy were the fortresses and walls systems in Korea. Many of these fortresses were situated on mountains and were designed to dominate passes and supply lines. They were also intended to be a refuge for civilians in times of war. These fortresses were defended by an excellent artillery arm, which was perhaps the best in Asia. This excellent artillery extended to its use in naval combat, where the Koreans relied upon the strategy of bombardment to destroy the enemy fleet.
Court politics and apathy, however, negated many of these advantages and highlighted several disadvantages to the Korean system of war. The fortress system, designed to provide a defense of depth, was marked by poorly designed fortresses that failed to take advantage of foundational defensive engineering techniques such as towers and areas designed to set up areas of cross-fire. In addition, many of the fortresses were poorly maintained. Adding to the fortress systems weakness was the Korean policy that local commanders could not take initiative in war until a general appointed by the court arrived on the scene. This served to isolate the defenders, as they could not move to assist each other until some time had passed. In addition, when the court appointed generals did arrive, they were often ignorant of the local terrain, troop strengths, and deployment. The generals themselves were often appointed based on social connections rather than skill, and so on average these generals were incompetent. The troops these generals led usually matched the incompetence of their generals. Korea had no standing field army at this time, and so relied on poorly armed, poorly trained levies.
In contrast, Japans strength was in its troops and generals. Japan had several notable generals, who combined natural talents with war experience earned through the recent Japanese unification under Nobunaga. These generals led highly trained and experienced armies which consisted mostly of arquebuses armed infantry. In preparation for the invasion, Japan had also expanded its naval capabilities. While the majority of this expansion was in the traditional Japanese naval tactics, which relied on speed and boarding actions, Nobunaga had used his contacts within the Jesuits to secure three Portuguese galleons.
Preparations for war were complete in Japan by 1592, and during the spring Sō Yoshitoshi set sail with close to fifteen thousand men. Sō Yoshitoshi was the daimyo of Tsushima near Korea and was knowledgeable of the surrounding terrain, leading to him to be selected to set up a bridgehead for the main army. This force landed at Busan, whose general was informed of the invasion but took no steps, not believing that the Japanese would actually dare invade his glorious nation. This belief proved unfounded, and under cover of arquebuses fire the city was stormed, resulting in the fall of Busan after a three day battle. As ordered, Yoshitoshi began fortifying Busan, waiting for the main army under Hashiba Hideyoshi to arrive.
Meanwhile, a Korean army under General Yi arrived outside of Busan. The lack of Japanese activity since the fall of Busan convinced General Yi that the invasion was merely a minor raid by the Japanese. As such, General Yi assembled about five thousand troops outside of Busan, planning on a quick strike to overrun the Japanese. The Korean charge, however, withered under Japanese gunfire, and a counter-attack completely encircled the Korean camp, leading to General Yis capture.
Yoshitoshi, taking advantage of General Yis defeat, moved to consolidate his position, taking almost the entirety of Gyeongsang Province. Meanwhile, the second division, close to twenty-five thousand men under command of Hashiba Hideyoshi disembarked at Busan and immediately moved northward, intending to capture Hanseong.[1]
He would face General Sin Rip, the Vice Minister of War, and the commander sent by the court to replace the captured General Yi. General Sin began fortifying Choryong pass, which the Japanese would have to pass through in order to reach Hanseong. General Sin had about fifteen thousand men, five thousand newly raised cavalry from the capital reinforced by eight thousand provincial levies and two thousand survivors from Busan.
The Battle of Choryong Pass went poorly from the start for the Koreans. Knowing that his cavalry was useless in the cramped, broken terrain of the pass, General Sin placed them in the rear of his forces. This, however, exposed his levies, who broke under the Japanese charge. General Sin attempted to lead his cavalry in a counter-charge, but they ran into the retreating infantry, causing even greater chaos.
The way through the pass clear, Hideyoshi advanced along the Han River unmolested, until he finally found a point he could cross with his army. Upon reaching Hanseong, he found the city abandoned and partially looted by the retreating Imperial Court. The Koreans next took up defensive lines along the Imjin River with eleven thousand men. Without boats, Hideyoshi proved unable to cross the Imjin River, resulting in the offensive stalling.
Meanwhile, Japanese reinforcements continued to flood Korea, bringing the total Japanese force in Korea to just shy of one hundred and fifty thousand men organized in seven divisions under the overall command of Hideyoshi. With the exception of Hideyoshis forces, which continued to look for a way to cross the Imjin River, the Japanese forces were deployed in securing the southern peninsula, which by this point was suffering under rebellions against the Japanese. Around this time the Japanese also began suffering from supply problems born from the Korean Admiral Yis naval successes.
Admiral Yi, along with Admiral Won, had been ambushing Japanese supply convoys, using intelligence gained from native fishermen. This led to the Japanese fleet, under Konishi Yukinaga, to receive orders to hunt down Admiral Yis fleet and destroy it. Yukinaga, believing that the Korean incompetence on land would be mirrored on the ocean, aggressively began to hunt down the Korean fleet. Unfortunately for him, not only did he face a naval arm much superior to the Korean army in quality and equipment, but he also faced one of the best Korean commanders, Admiral Yi. The first engagement turned into a disaster for the Japanese, as the Koreans used the Japanese aggressiveness against them, using a fake retreat to draw out the Japanese before crushing them.
Now even more determined to crush Admiral Yi, Nobunaga attached his precious Portuguese galleons to Yukinagas force. This time, the hunt took them almost to Yis base at Yeosu before meeting. Though the battle was more even than the previous lopsided defeat, Admiral Yi used the shallow water and local knowledge to his advantage. In addition, he too had a new weapon, two Kobuksons, which he used to attack the Japanese line, throwing it in confusion. In addition to being extremely fast, powered by both sails and oars, the Kobuksons, with their flat bottom, were more maneuverable in the shallower waters. Though the galleons sunk one of the Kobuksons, after one of the galleons ran aground, the others withdrew, worried about suffering a similar fate, which would leave them helpless. Their trump card having fled, the rest of the Japanese forces quickly followed suit, leaving many of their ships behind.
After this defeat, Nobunaga forbade Yukinaga from engaging Admiral Yi directly. Instead, Nobunaga ordered Nabeshima Naoshige, together with fifteen thousand men, to assault Yeosu from the landward side. Meanwhile, at sea, Nobunaga attempted to neutralize Admiral Yis impact on the supply route by instituting a convoy system revolving around his Portuguese galleons, which he believed would be superior in open ocean waters to Yis forces.
Resisting the Japanese land invasion primarily fell to Gwak Jae-u, a former land owner, who had raised a militia of about five thousand men to resist the Japanese. Later, various militia and semi-regular troops raised his troop total up to ten thousand men. Knowing that he could not meet the Japanese in open battle, Gwak resorted to guerilla warfare. Despite the harassing attacks, the Japanese managed to arrive at and besiege Jinju, the key castle in the defense of Jeolla Province, of which Yeosu was the capital. Supply problems hampered the siege, as the Korean guerillas effectively denied the besieging army resupply. This forced Naoshiges hand, causing him to order a general assault in hopes of quickly ending the resistance. Under suppressing fire from their arquebuses, the Japanese stormed the castle. Though originally futile, the Korean commander was eventually killed in the fighting, causing the garrison to lose heart. Seeing their chance, the Japanese pressed the attack. A late attempt at a diversionary attack by Gwaks guerillas did not prevent the fall of the castle, though it did buy the garrison time to raze the castle and withdraw in an orderly fashion.
With the fall of Jinju, Admiral Yi knew that he could not long stay in Yeosu, and so he was forced to sail northward to where he could establish a safer base. As a result of Yis withdraw, the Japanese supply situation improved drastically.
As 1592 drew to a close, the Japanese looked to be in a good situation. Though failing in their original goal of sweeping through Korea in their march on China, the Japanese did successfully take Hanseong, along with most of the country. For the most part, the south was under Japanese control, though rebellious militia groups continued to roam the countryside. By the end of the year, the Japanese supply situation had improved markedly, allowing Hideyoshi to confidently declare to Nobunaga that he would be able to break through the Imjin Rivers defenses in the spring.
But unfortunately for the Japanese, they were not the only ones who were predicting a renewed offensive for the Japanese in the spring. In the court of the Ming Emperor, the Emperor, under the influence of Korean diplomats, saw the Japanese threat as one that could no longer be ignored. With Japanese successes, the Emperor decided that the threat must be met by what he saw as an overwhelming force. And so, the decree went out. One hundred thousand men would march into Korea to teach the insolent Japanese a lesson.
[1]Seoul
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