Korean military reform before Imjin War?

Hideyoshi's invasion of Korean was characterised by Japanese victories on land and Korean victories at sea. This was due largely to the defense policies of the two nations. The Korean navy was a professional force used to dealing with wokou raiders, while the tactics, organisation and technology of the Korean land forces were a mess. The Japanese were the most professional military force in Asia, battle-hardened from the fight to unify the country and armed with arquebuses and muskets acquired from the Portugeuse.

The Koreans had an exagerratedly negative idea of Japanese power and military capability, and this contributed to their horrendous losses early in the war. Some, such as the later-Prime Minister Yu Seong-ryong, appealed for military reform and the adoption of the arquebus into Korean armies, but his views were ignored by the Yi Court and opposed by most of the government factions.

What if they had heeded the warning signs? Let's say that the ambassadors from Joseon to Japan are better able to express the military efficiency and intention of the Japanese (as opposed to OTL where they sent mainly mixed signals). Something might need to be done to curb the factional politics of this era, but I suggest that an overwhelming dominance by Yu Seong-ryong's Southern Faction (perhaps if the rival Northern and Western factions fracture through internal squabblings and scandal) could spearhead a military reorganisation effort. Timely aggression from the Jurchens in the north could help too.

Something like the Hunnyeon Dogam (central military bases set up to defend Korea during the Imjin war in OTL 1593) is set up earlier, perhaps in 1589, and a more organised system of defense for the peninsula is developed with a permanent standing military. The problems of military-promotion-via-connections is reduced something and more flexibility of action is given to local commanders in times of national emergency. Finally, the arquebus is brought into general service. Perhaps a positive relationship could be cultivated with the Portugeuse, with their traders being allowed into one of Joseon's southern ports (this is all before Korea developed its hermit kingdom reputation, and precedence exists for foreign traders in Korean ports).

Thus, if Hideyoshi invades in 1592, he has lost much of his military edge on the ground. What happens next? I assume that the Japanese will still have an advantage over the Koreans in land battles due to experience and the size of the invading army. However, if the Koreans are able to hold the line it is likely that Korean naval dominance will help to cut the Japanese from supplies. Meanwhile, a disciplined Korean army would have a much better track record than the hapharzardly organised recruits of OTL. Even assuming that the arquebus hadn't been yet fully introduced, Korean archers of the period had better range, accuracy and penetration.

Japanese progress in the war will be much slower, and if they are prevented from capturing Hanseong things will become increasingly dire. Korean naval victories will limit supplies for the Japanese armies. If the Ming intervene as in OTL that'll be it. If the Koreans can defeat the Japanese without the Ming it may be just as significant.

Assuming a Japanese fiasco in Korea, what are the effects? Hideyoshi would lose prestige, and the threat of instability by the ambitious in Japan would be greatly increased. Korea's military reform agenda would likely be accelerated, as much of the remaining dead wood cleared out by the experience fighting the Japanese invaders. The Koreans might wish to carry out a reprisal action of their own, though might be restrained by the Ming.

A more technologically advanced, military adept and confident Korea would make things interesting for the Jurchens (and potentially for the Ming if things get out of hand). A Japan returned to the bad old days of disunification would keep things interesting. Portugeuse guns that keep flowing into Korean (new defense policies) and Japanese (new instability) ports would also have effects.

Any thoughts?
 
Were the Koreans ever able to actually take a Japanese castle during the war with Korea? Do they get cannons too as well as guns? It strikes me very much as an analogue of the 100 years war actually.
 
There were no actions on Japan itself during the war, and most of the castles in Korea itself were poorly constructed with low walls. The Koreans already possessed advanced cannons and rockets, with longer ranges than the Japanese heavy artillery, which were used highly effectively in naval engagements. The Japanese technical advantage was slim, but they were simply more professional fighters. Korean bows were superior to Japanese bows and in some ways superior to the arquebuses, but the Korean soldiers were undisciplined green recruits and the defence policies were a disaster. The PoD should result in a better trained archers and soldiers willing to stand their ground, both of which would be far more effective than the arquebuses.
 
I meant the fortresses Japan built in Korea. Stuff I've read indicates that the Koreans were simply incapable of ever taking a Japanese castle built in Korea.
 
Not necessarily. The Koreans and Ming were almost able to take the castle at Ulsan in 1597, but Japanese reinforcements arrived and forced a stalemate.
 

Sior

Banned
230px-Hwacha2.jpg

http://en.wikipedia.org/wiki/Hwacha
The hwacha was a brainchild of its predecessors, the Juhwa and the Singijeon. The first hwacha was made in 1409 during the Joseon Dynasty by several Korean scientists --including Yi Do (이도) (李蹈) and Choi Hae-san (최해산) (崔海山)[2]. It is unlikely that the hwachas made around this time participated in combat[3].

During the rule of Sejong the Great, hwachas were further developed and extensively made. Records shows that during this time 90 hwachas were in use. King Sejong, famous for his contribution to Hangul, made efforts to improve the hwacha and by the end of his rule; by the time he was through, a single hwacha could fire 200 rocket arrows at one time.

Stronger and more effective hwachas were made in 1451 under the decree of King Munjong[4]. At the time, 50 units were deployed in Hansung (present-day Seoul), and another 80 on the northern border. By the end of 1451, hundreds of hwachas were deployed throughout the peninsula[5].

Role during the Japanese invasions of Korea (1592-1598)

Hwachas saw action most extensively during the Japanese invasions of Korea against the Japanese soldiers. They were mostly placed in fortresses or citadels [6] and used in defensive manners. These proved to be powerful in many battles, and were most prominent in the Battle of Haengju, in which 3,400 Koreans repulsed 30,000 Japanese with the help of 40 hwachas.

Hwachas were also used in panokseons under the navy of Admiral Yi Sun-sin to attack Japanese ships from a distance.

The Japanese samurai ground troops, especially in the Battle of Haengju, typically advanced in dense formations, presenting ideal targets for the hwacha. ...
 
The Korean artillery was indeed highly developed and effective, as was its navy. The problem was it's small, unprofessional, ragtag army and it's highly inefficient defensive policies.
 
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