Buildup for the Four Armies Conquest and the Ming Dynasty's Predicament
I immediately showed Yi Bang-won the letter from the Ganggye Garrison's military commander upon arriving at his side.
"Hm. As expected, the Jurchens near the Yalu River are stirring up trouble. It seems the prolonged civil war in the Ming Dynasty has led them to believe they can build their strength in the Liaodong region and start rebelling."
"Yes, Your Highness. That appears to be the case. However, beyond that, our establishment of the Six Garrisons seems to have made them feel threatened."
According to the latest reports from our scouts, the Six Garrisons area was steadily solidifying as Joseon territory, and the tribes beyond the Tumen River were increasingly incorporating themselves into our sphere of influence as vassals. This had them quite frightened. It was all thanks to Hwang Hui faithfully executing the systems I had put in place. Hwang Hui really gets things done right. He just needed to tough it out there for another year or so. When he returned, I would make sure to assign him directly under me.
In any case, it was true that the Jurchens north of Ganggye, now bordering our Joseon lands, were living in fear. On top of that, as Yi Bang-won had pointed out, the Ming's extended civil war meant they couldn't pay attention to the Jurchens in Liaodong. Their control was limited to using Ahechu, the Jianzhou Left Guard Commandant, to manage the other tribes. Ahechu had received trading rights from the Ming along with his Jianzhou Guard position and was expanding his influence by selling horses to the Ming as they demanded for their civil war—just feeding the tiger's cub, though.
Could this Ahechu guy be connected to Yimanju somehow? He gives off that same vibe. In any event, the unrest among the Jurchens north of Ganggye posed a serious threat to our Northwest Frontier. Especially since beyond that area lay the Yalu River, and they could potentially draw in Jurchens from across it to invade Joseon.
"What are your thoughts, Minister of War?"
"It would be best to establish a new garrison there to bolster our defenses."
I promptly suggested to Yi Bang-won that we fix Joseon's defensive line along the Yalu and Tumen Rivers as boundaries. He pondered it deeply before responding.
"That's a good idea. But given our current situation, it's not feasible right now. The Six Garrisons have only just stabilized, and launching another military operation wouldn't be advisable. Especially since we don't know what news the envoys to Japan will bring back. If the Japanese provoke us repeatedly, we'll need to build new warships to punish them, so raising troops now isn't wise. As the prime ministers say, our military budget is limited—we can't confront both the Jurchens and the Japanese at once."
With the Six Garrisons now stabilizing and their military expenditures dropping significantly, it was true we had some breathing room. But as Yi Bang-won noted, we couldn't predict Japan's moves, making it hard to mobilize for pioneering the Four Armies. Still, if my assumptions held, Japan would likely take a friendly stance toward us, so preparing the buildup for the Four Armies wasn't a bad idea. They wanted trade with the Ming, and they'd hope we'd mediate, so they'd come around. Of course, the Ming would only allow token tribute trade to save face, prompting the Japanese to resume piracy again.
Whatever— we'd deal with that later. For now, we needed to focus on Joseon's interests.
"You're right; it's difficult at the moment. For now, dispatching five hundred Yeheung Guard cavalry to Ganggye to reinforce its defenses would be best."
"Yes, that seems prudent for the time being."
"And we should survey the area north of Ganggye in detail, preparing for future conquest."
"Hm. So you believe we must seize it, Minister."
"Yes. Defining Joseon's borders along the rivers is essential for our northern defenses. Even if it's tough now, thorough preparations could allow us to proceed steadily in four years' time."
The Four Armies and Six Garrisons differed greatly in pioneering difficulty. For the Six Garrisons, supplies could be shipped by sea if needed, and the area had plenty of arable land. But the Four Armies region was the most remote part of the entire Korean Peninsula. Conquering and stabilizing it would take even longer than the Six Garrisons. Thus, using the Four Armies conquest and stabilization as an excuse to head to the frontier would buy me at least four years away from here.
Four years of buildup, followed by four years of conquest and stabilization—eight years total. Perfect. Of course, my new warship project might fall through, but if I could persuade Yi Bang-won to build one or two prototypes now, we could mass-produce them later after fixing any issues. That might even be better.
"But we'll need the Ming's approval. As you say, it involves military action north of the Yalu."
"Yes, Your Highness. If necessary, I can go to the Ming and negotiate myself."
"Not a bad idea. But you're not planning to lead the conquest north of Ganggye yourself, are you?"
How did he know?
"There's no need for you to go north of Ganggye, Minister. It's better if you stay in the capital and oversee military affairs. Why do you keep trying to head to the frontiers? I need you here."
Damn, shot down immediately. I needed another excuse. I had to get away from that water ghost Crown Prince Yangnyeong no matter what.
"We'll discuss it at the next council meeting. Repeat exactly what you told me there. Just don't mention conquering north of Ganggye—I'll review that separately."
"Yes, Your Highness."
"Good. The Wonangjin formation is progressing well, but how goes the training of specialized hwapo artillery troops? I haven't received a proper report yet, so I'm curious."
"We're selecting personnel now, with Choi Yun-deok appointed as commander. It will take some time, though."
"With hwapo improvements needed too, it'll take time. Don't push too hard."
"Yes, Your Highness."
Then Yi Bang-won added,
"By the way, Minister, what do you think of the chances the Ming will demand cavalry reinforcements?"
"High, Your Highness. But in my view, it won't happen until next year."
The Ming civil war showed no signs of ending. Whether due to Gwak Yeong's cautious nature or not, after one major battle, he had avoided decisive engagements, opting for a war of attrition to pressure them. It was the best strategy for the suppression army, outnumbered but with superior quality troops. But if it was the Zhu Yunwen I knew, he wouldn't like this approach and would demand a decisive battle. His close aides felt the same—they wanted to end the civil war quickly.
So another major battle was inevitable, probably around winter this year. And they'd lose for sure. Seo Hwi-jo was there, but victory was impossible now. The idiotic order not to kill Zhu Di's main force, lack of cavalry, and poor adaptation to the Hebei climate were to blame. After the defeat, they'd regroup and likely buy horses in bulk from us or demand cavalry. Especially with Hwang Ja-jing appointed as Minister of Rites, the odds of a cavalry request were even higher. He'd long advocated borrowing Joseon's cavalry instead of training their own—it was cheaper and faster.
"If you think so, we still have time. In the meantime, do what needs doing."
"Yes, Your Highness."
With that, I shared my views with Yi Bang-won and returned to the Ministry of War to continue military reforms.
The next day, Yi Bang-won convened a council meeting, informing them of the potential Jurchen unrest north of Ganggye and asking for countermeasures. Most officials suggested reinforcing Ganggye's defenses and building fortresses there.
I repeated exactly what I'd told Yi Bang-won. Surprisingly, many agreed, including the Office of the Inspector General and the Office of Censors. These guys are impossible to pin down. They criticized my spending one moment, then supported me the next. Was military spending on smashing Jurchens not a waste to them? No—building fortresses cost more than dispatching cavalry to check them and surveying north of Ganggye. They probably would've frothed at the mouth if I'd pushed for conquest.
In the end, five hundred Yeheung Guard cavalry were dispatched to Ganggye, and I pressed on with military reforms.
Thinking it over, linking the Four Armies conquest to the Ming's cavalry demand could work well. We could slip in approval for military action north of the Yalu and Four Armies occupation in exchange. Post-civil war, the Ming court would be busy with aftermath and struggling to control Liaodong Jurchens, so they'd likely accept. But it was a bad deal for us—we needed more. Like repatriating Koryo people from Beiping. Massive gifts as standard, of course. I'd have to mull it over.
Thus, while pondering how to extract more from the Ming, I advanced the military reforms.
Meanwhile, around this time, a massive battle erupted in the Ming Dynasty. Min Mu-jil had expected war only in winter, but Zhu Yunwen and his aides' desire for a quick decisive battle led to a clash between Gwak Yeong's suppression army and Zhu Di's forces in August. The suppression army suffered devastating losses—nearly seventy thousand of their three hundred thousand troops killed. Zhu Di lost over ten thousand, barely preventing a frontline collapse.
Seo Hwi-jo fought valiantly, but southern soldiers unadapted to Hebei weather, lower troop skill, and cavalry shortages doomed them. Above all, Zhu Yunwen's order not to kill Zhu Di was the root problem. Despite Zhu Di personally slaying countless foes, they couldn't target him, allowing his elite cavalry to rampage.
The suppression army withdrew with heavy casualties, resuming defense of key points and attrition warfare per Gwak Yeong's orders.
Faced with this, Zhu Yunwen consulted his aides. Minister of War Cheol Hyeon said,
"We need a strong cavalry force to counter Prince Yan Zhu Di's elite cavalry. Unfortunately, we lack one."
"Can't we just buy more horses from Joseon?"
"Your Majesty, even with horses, we lack riders. Training them would take too much time."
The civil war had depleted their cavalry, a key reason they couldn't beat Zhu Di—though the no-kill order was paramount, and Zhu Yunwen showed no sign of revoking it, so Cheol Hyeon cited the next issue.
Zhu Yunwen sought solutions, and Minister of Rites Hwang Ja-jing proposed,
"We should borrow cavalry from Joseon. They've always had strong cavalry and can match Prince Yan's well."
He argued training would take at least a year—time the Ming couldn't afford when ending the war quickly for national recovery was urgent.
Minister of Revenue Je Tae countered,
"Their demands will be steep. Cavalry aren't cheap."
"We can grant them gifts and titles. Minister of Revenue, rebuilding cavalry costs more—this is cheaper."
Hwang Ja-jing offered to go as envoy himself. Zhu Yunwen polled his aides, and after debate, they decided to request Joseon cavalry—cheaper than raising their own, and siding with them would demoralize Zhu Di's forces.
Thus, the Ming court dispatched envoys to Joseon for cavalry reinforcements, with Hwang Ja-jing leading. Though unnecessary for a high minister like the Minister of Rites, he volunteered—having pushed hardest for this battle, he took responsibility. He truly despised Zhu Di and was determined to eliminate him at any cost.
This occurred on November 5, 1402.