The Korean navy in the mid-1630s is not large or what would be considered a blue-water navy by the likes of the Romans, Omani, or Spanish. While Korean merchants sail to Japan and occasionally further afield, for protection they are dependent on the naval forces based in their destinations. Given the landward focus of Korean foreign policy since the Tieh yoke was overthrown, the army has sucked up most Korean military expenditure. The need to defend the coast against Japanese wokou provided some impetus for a strong navy, but with the unification of Japan that impetus has waned.
The Korean navy is a coastal defense force comprised almost entirely of panokseon vessels, multi-decked vessels propelled by a mix of oar and sail. Romans who see them call them the Korean version of an Andrean dromon, the Roman term for a galleass. Despite the oars, due to their thick planking they are fairly slow, but at the same time said thick planking enables them to stand up well to enemy gunfire.
The main strength, from the Korean viewpoint, is their small turning radius and shallow draft. The Korean coast is strewn with small islands and narrow channels, often with treacherous currents. Having warships that can deploy and maneuver through these tight waterways is crucial to defending the region. A western-style battle-line ship has far greater firepower, but all the cannons in the world cannot do any good if they cannot be deployed where needed.
An individual panokseon would be horribly outmatched in a one-on-one gun duel with a battle-line ship, but that is less of a drawback than it sounds. After all, the only thing that can stand up to a battle-line ship in a duel is another battle-line ship. Compared to almost everything else, panokseon are heavily armed.
Panokseon vary in size, the largest ones up to 30 meters, comparable in length to Roman and Spanish fregatai and with similar firepower. While the number of hulls registered to the Korean navy in 1635 has declined in the past few decades, the overall trend is to larger panokseon. These larger ships mount anywhere from 20-50 cannons, although the higher numbers would include a large percentage of light anti-personnel cannon in their totals, rather than just anti-ship ordnance. [1]
The relative unimportance of the navy in pre-war Korean military thought is clearly shown by the complete inexperience of the naval commanders appointed. Yi Sun-sin is a military veteran, but as a cavalry officer fighting against recalcitrant Jurchens. Prior to his appointment as fleet commander, he’d never been on a warship that had fired its cannons at even a practice target, much less fought in a sea battle.
The Zeng, with their base in southern China and maritime connections, had been a respectable naval power at their beginning. But they’d never quite recovered from the bloodletting at the battle of Pyrgos and with first continuing warfare in the north and then the establishment of Luoyang as their capital, the Zeng are decisively turning away from the sea.
At the start of the Eulhae War [2] though that process is not complete. While Chinese trade is conducted with the outside world through Pyrgos, there is still a decent amount of sea traffic between Chinese port cities. This unsurprisingly has attracted pirates. The unification of Japan and the concentration of Roman trade at Pyrgos has lessened the official backing said pirates can get but there are still plenty of free-lance pirates around to cause trouble. Many of these base themselves from small settlements on Kiponissi [3], which while claimed by both the Chinese and the Katepanate of Pyrgos is really controlled by the natives save for the pirate enclaves.
Thus the Chinese have a large navy at their disposal, at least in terms of numbers. Unlike the Korean panokseon which is propelled by oar or sail, the Chinese use sail-powered war junks. Like the panokseon, these can vary wildly in size with larger war junks comparable to small battle-line ships and mounting a similar number of guns, although most are of a smaller bore. The Chinese have a few of these great war junks, but the vast majority are much smaller and lightly armed. The Chinese fleet is geared to running down smugglers and chasing off raiders, not slugging it out with another war fleet.
Li Rusong’s primary goal in 1636 is Seoul, the Korean capital. While there is no guarantee taking it would be a knockout punch, it would be a devastating psychological and strategic blow. As he marches southward, he does not face an enemy army in pitched battle but instead a swarm of small forces, the Righteous Armies of the yangban and peasants as well as the monastic troops. In a direct field confrontation with anything approaching equal numbers, the Korean forces break quickly against Chinese troops, but they snap at foraging parties, scouting groups, and isolated detachments. Furthermore, when defending castle or town walls, they are much better at going toe-to-toe with the Chinese army although their lack of artillery is a serious disadvantage.
By the summer of 1636 the regular Korean army is expanding rapidly as new recruits come in, but the organization as a whole suffers much from the loss of veteran troops and officers, as well as equipment. In fighting the Jurchens the Koreans relied much on the bow, as their firearms are still matchlocks. However most of their best archers perished in Won Gyun’s debacle and it takes years to train a proficient archer. Matchlock-men can be trained far more quickly, but most of the Korean matchlocks were also lost in the same debacle and given the low demand for them in the past, Korean gun production is startlingly low. Some compensation comes from Korean proficiency with and number of cannon, but the best Korean artillery-gunners were again lost in the north and those skillsets cannot be built up rapidly.
The Koreans are working rapidly, and effectively, to shore up these weaknesses, but even the best efforts take time which is not available. To compensate, the Koreans plan to use the Japanese troops being sent over. The Japanese are willing to cooperate, but considering that they will be contributing the bulk of the regular forces, insist that the commander of the expeditionary force, Konishi Yukinaga, also be placed in command of all allied ground forces. Reluctantly King Danjong agrees, but only after extracting a pledge that Yi Sun-sin will be in command of all allied naval forces.
The Japanese can field an extremely large army but getting it to the field of battle is another matter. They are also terrified of the prospect of Chinese war junks getting loose amid heavily-laden troop transports, so the Japanese host is ferried over in stages to Busan to begin the long march north. Much to Yi Sun-sin’s annoyance, he is tied up in convoy escort duties as this takes place, and it is a long process.
Meanwhile Li Rusong’s progress south is bloody but steady, overwhelming all opposition with a major victory against a mix of Korean regulars, irregulars, and a Japanese contingent garrisoning Sariwon. Nevertheless as Chinese forces enter the Yesong River valley and follow it south to the sea, resistance only increases. Opposition to the Chinese, and the blood price it demands, is paid mainly by the Righteous Armies, but (green) Korean regulars and more Japanese troops are steadily arriving in theater as the summer passes.
By the time Li Rusong reaches the Yesong delta, his supply lines are under such strain from the guerrilla tactics that he is forced to march not southeast toward Kaesong and Seoul, as he would wish, but west to secure the port of Haeju. The Righteous Armies are playing havoc with the supply convoys on land but are toothless at sea, so if he can take Haeju for use as a supply base, it will immeasurably ease the strain on his logistics.
Haeju is held by two Righteous Armies, one under the command of a local yangban Yi Kwang and the other under the Buddhist abbot Hyujŭng. Both of them have sworn to fight to the death and rally their men to do the same. They have no answer to the storm of Chinese cannon fire but they fight in the rubble of the battlements, in the ruins of the city, contesting each and every block as they are steadily ground down into dust. Korean losses are unknown, but estimated as high as 11000, far higher than the reported Chinese 1800, but they cost Li Rusong two precious weeks and burn the docks at the end. Chinese engineers promptly set to work restoring them but it is clear Haeju will be no panacea for the Chinese supply issues.
Once Haeju is secure and naval stores start arriving, Li resumes track for Kaesong. It, along with whatever defense could be mounted at the Imjin River, is the only remaining serious obstacle between him and Seoul. But in those weeks taken up by Haeju, the Kaesong garrison has ballooned from 7500 to 28000, including four thousand Japanese armed with flintlock muskets, while laborers have reinforced the defenses with piles of packed earth.
The siege is brutal on both sides. Li Rusong pounds on the Kaesong battlements while the garrison gives back with equal fury, while Korean and Japanese troops arriving from the south harass the Chinese camp. When Konishi Yukinaga arrives in person finally with the bulk of the Japanese expedition, he launches a major attack on the Chinese camp. It is beaten back, largely due to the Chinese field fortifications, but losses are heavy on both sides and Li’s troops are becoming irreplaceable. Furthermore a few Korean and Japanese parties manage to make it inside the walls of Kaesong with critical supplies of rice and gunpowder.
A week later at the beginning of September, Yi Sun-sin, finally free from convoy escort duties, arrives on the scene. The Chinese fleet, which has faced hardly any opposition thus far, has been ravaging the Korean coast with scores of villages looted and burned, their squadrons scattering in the process. Over a three-week period, Yi wages and wins four separate sea battles against Chinese contingents, using the same tactics in all the engagements. Experienced in fighting the Jurchen on land, Yi follows the book he knows. He uses the Roman and Japanese (who have a mix of eastern-style junks and smaller western-style warships) vessels as relatively immobile infantry/artillery with more mobile panokseon as ‘cavalry’ that can harass and flank enemy forces.
In each battle, a small force challenges the Chinese who are in the middle of raiding, which retreats to open waters as the Chinese pursue into the ambushing main fleet. The heavy-armed but sluggish Roman and Japanese warships are stationed in the center of the allied line, where their gunfire disorders the Chinese advance as the panokseons swing to the side and smash into the Chinese from both flanks. By the end of September, Yi has destroyed 61 Chinese ships of varying size at the cost of 5 of his own, while Leo Kalomeros has shown much skill in playing the bait and needling the Chinese into giving chase. The lopsided score is somewhat less impressive when one realizes that due to the scattered nature of the Chinese fleet, in every battle Yi has a numerical advantage of at least 5-to-1.
Casualties on the Chinese side are extremely heavy as Yi deliberately drew the Chinese squadrons into deeper waters to increase their losses. If they’d fought in the shallows, Chinese sailors could’ve run their ships aground and fled on land. That would not do; Yi wants their heads, or at least their ears. Many are salted down for shipment to Seoul as demonstrations of their victory.
The fifth battle, fought at the entrance of Haeju Bay, is much more significant on a strategic level, although as far as combat goes it was the easiest from the allied perspective. Instead of a raiding warship squadron being destroyed, it is an important supply convoy carrying provisions Li considers crucial for continuing the siege at Kaesong. When news arrives of the convoy’s destruction, he is forced to abandon the assault, retreating back to the Yesong River, although an allied effort to harass him is mauled in the process.
Fighting continues on land as the two armies bicker at the Yesong, but neither commits to a serious push. Li is waiting for more supplies and reinforcements while Konishi has learned a healthy respect for Chinese field fortifications. Sending weapons and trainers to the Righteous Armies, he does all he can to encourage their depredations against Chinese outposts and convoys. This is at odds with the policy of the Seoul court, which is wary of the increased military power of the yangban and monasteries exemplified by the Righteous Armies and views them more as a threat to its own authority rather than an aid against the Chinese.
At sea Yi prowls but after the destruction of the convoy can find precious little to fight. He blockades Haeju for a time but has to break station as his forces are all running low on powder, an issue also facing the allied armies after the intensive fighting at Kaesong. Korean powder production, like their manufacture of matchlocks, is unimpressive and comes far short of the demands being placed on it.
Despite the carnage and the suffering and the difficulties felt by both sides, as 1636 wanes there is little sign that the Chinese, Japanese, or Koreans intend to give way. The Jingtai Emperor is disappointed but still approves of Li Rusong’s leadership (less so his naval commanders) and Luoyang commits even more troops and supplies to the fight. The Japanese alliance only proves that Korea is even more of a threat to the Middle Kingdom than was supposed. [4]
[1] Regarding turtle ships, I am drawing entirely from Samuel Hawley’s
The Imjin War: Japan’s Sixteenth Century Invasion of Korea and Attempt to Conquer China (which I highly recommend). He argues, convincingly in my mind, against the idea of turtle ships being ironclads. He has several arguments. There is no contemporary evidence for iron plating being used on the turtle’s back, which certainly would’ve been noted by the many Korean sources. Yi Sun-sin had limited resources when he built his first turtle ships. If he’d tried to armor his ships, he probably wouldn’t have had any metals with which to make cannons, which defeats the point of having the warship in the first place.
The turtle ships were certainly armored, but likely by thick wooden planking and perhaps seawater-soaked mats as protection against incendiaries. Japanese warships were lightly armed, mostly with firearms and not with cannon (Toyotomi tried and failed to get Portuguese warships for the invasion), so that would’ve been armor enough. The ‘turtle ironclad’ argument probably derives from the West. Widespread knowledge of Korea and the Imjin War in the West only came about in the mid-1800s and the reports of armored Korean ships were confused with the new ironclads of the American Civil War. See pgs. 195-98.
Given these arguments, turtle ships will not be appearing ITTL. Against the 1630s Zeng Chinese ships, much better equipped with cannon than OTL 1590s Japanese ships, turtle ships do not seem useful.
[2] The Korean and most commonly used name for the conflict. It is derived from the Korean year Eulhae that corresponds to the western year 1635, when the war is commonly considered to have started in earnest; the opening gambit in 1634 is often ignored. (This is from the OTL Imjin War, which gets its name as the Japanese invaded in 1592, Imjin being the Korean year name at that time.)
[3] OTL Taiwan. The name is Greek.
[4] The reinforcements are partly financed by silver gotten in trade at Pyrgos. While there is no formal agreement, the Chinese, Romans, and Japanese all continue to trade at Pyrgos as if nothing were amiss. The trade is far too lucrative for all parties to let something like a war disrupt it.