The Yeo-Mong War
At the outbreak of war with the Mongols, Father had assembled an army of 100,000 at his headquarters. 15,000 iron cannon troops, 45,000 long-spearmen manning the wagon forts, 20,000 archers, 10,000 cavalry, and 10,000 artillery and engineers. Plus 3,000 for command and logistics. A total force of 103,000, fully prepared.
And Chae Songnyeon, Yi Jaseong, and Kim Heije were each assigned to command one of the K-Tercio iron cannon wagon fort formations. Originally there were four such formations—so where was the fourth one?
"Father. Father, please."
"How can you say such things? You're a woman."
Why was I saying this? The problem was that Choi U himself wanted to command it personally. Sure, I'd passed it off as a strategy I'd cooked up with the mountain spirit, but still.
"Even the Khitan's Regent Empress personally repelled the Song forces. Besides, the iron cannon wagon fort is a strategy I devised head-to-head with the mountain spirit. Let me step forward. As your successor, is it right for me to stand idly by in this war?"
Once decided as successor, gender no longer mattered. I needed to rack up achievements.
"Hmm, I see. But you must be careful. Take command of the wagon fort in the rear, where I can rescue you at any moment."
After begging and pleading relentlessly, I finally got command of one iron cannon wagon fort formation. That left Father to direct the cavalry, archers, and artillery from the rear.
Before departure, Father paid respects to the emperor in the throne hall—not merely receiving the battle axe, but demanding it outright. Then, before the assembled troops and generals outside Gaegyeong, he raised the battle axe high.
"Soldiers of Goryeo, hear me! We are descendants of mighty Goguryeo, who withstood millions from the unified empire of Sui! Shall we bow our heads to these barbarians freshly risen from the steppes? Even mighty Khitan was crushed at Gwiju in the past—now we, their successors, advance to shatter the Mongols' momentum! Long live Greater Goguryeo! Long live His Imperial Majesty!"
Waaaaaaaaah!
Unlike the historical three armies, this rapidly assembled force of 100,000 finally began its march north. En route, we repeatedly drilled the rotational strategy on the Gwiju plains.
"Place the iron cannon wagon forts on the left and right flanks in front and rear echelons. In the center terrain, we'll bury a minefield. It might look like you're in danger if they break through the center, but once they see the mines' power, the Mongols won't dare approach."
"Artillery overseer, do you know what a minefield is?"
"It's like this. Bring him."
At my order to the Byeolcho Army, they dragged in a man. A thoroughly vile-looking one.
"Urk! Why am I being treated like this? Hyung! Hyung! Forgive me!"
"Uncle, do you remember me?"
Unlike your sleazy face, do you recall your cute niece?
"You're Yeon, aren't you? Talk to your father for me!"
"That's why I've convinced Father to give you a chance at life. See that? The support there. Step on it."
"What the hell is that?"
"A weapon test. Better than dying, right?"
Choi Hyang, hearing he could live, decided to step on the mine. Bluntly, between dying outright or testing a weapon, which is better? Having been through hell and back, he chose the mine.
"This little—"
BOOM!
And so my uncle met a spectacular end. My private troops promptly dragged off his corpse, as if waiting.
"You saw it. More than enough to kill a man. These will be buried across the Gwiju plains by engineers, and the Mongols will bear the brunt."
Everyone's jaws dropped. Why the shock?
After a frozen silence, Father spoke.
"My brother twice plotted against me. Giving that sinner a chance to test a new weapon made for Goryeo's sake—what could be better?"
Exactly. That's what I'd been saying. This uncle had already pulled his shit twice. If he'd won the power struggle, I'd be dead or a slave at best, and Father would be gone. In original history, Choi Hyang rebelled and was crushed by Chae Songnyeon, Jibyeongmasa Wangyu, and Busa Kim Uiyul with 10,000 troops. Here, we nipped it faster. Anyway, he was in our way.
"I think the weapon test was sufficient. We'll counter their attacks with the four wagon forts."
"If they push the center, the mines will blow."
From simulations, the Mongols would panic at the minefield, and we'd press with the iron cannon wagon forts.
"Yes. Meanwhile, our wagon forts advance. We've improved the wagons considerably, so even with obstacles, we can shove through and pressure the Mongols. At that moment, spears thrusting from the wagons will skewer their horses, panicking them. Infantry won't stand a chance."
From behind, archers rain arrows, cannons at key spots unleash shells—what can they do?
"By the way, any word on Hamsinjin? Didn't we send scouts?"
They said holding, but by now maybe overrun, Iron Preface not arrived?
"Your Excellency! Your Excellency! General Kim Gyeongson at Hamsinjin still holds! Beacon confirmed!"
"Kim Gyeongson holds?"
Then we can readjust.
"The Mongols might revise their strategy too."
"What do you mean?"
"They've been stalled nearly a month at Hamsinjin. Other forts intact. With our main army at Gwiju, how will they respond?"
"They might think other forts tough even if they take Hamsinjin, or smash our main force to end the war."
"Exactly. If they bite, we minimize losses."
Maybe this first Yeo-Mong War ends with Hamsinjin and Gwiju battles.
Hamsinjin
BOOM! Stone cannons began pounding the walls. Hamsinjin wasn't originally a formidable fortress. Recently reinforced against Mongol incursions, but compared to Gwiju, fortified against Khitan, it fell short. In original history, when Kim Gyeongson fought at Gwiju, Iron Preface and others had slowed Mongols somewhat. Here, it faced them first.
Still, Kim Gyeongson's 5,000 held fiercely. Recent reforms strengthened provincial Byeolcho, buying rear time.
"Pour rocks! Loose arrows!"
Mongols showered stones and arrows.
"Block them! Fire back!"
Attackers vs. defenders. But fiercer resistance than expected had Salitai digging under.
Tunneling to breach. "Attack fiercely, and dig! Infiltrate and open the gates!"
But Kim Gyeongson read it. Mongols tunneling met Goryeo welcome: boiling oil.
"Come on in."
Grinning Goryeo troops dumped it.
"Gaaaaah! Help!"
"My... eyes! Eyes melting!"
Tunnelers cooked by Goryeo chefs' oil control.
"These barbarians! Think Goryeo easy?"
"Even Jin, who crushed Song, dared not invade us!"
Tunneling failed. But damage mounted. Walls cracking under stone fire—not quick end.
Time to use it.
Kim Gyeongson recalled recent iron cannon Byeolcho training from headquarters. Odd weapon: cannon. Power immense—shredding siege gear with iron balls.
"Lord! Catapult stones exhausted!"
How long fought? Trebuchet ammo gone.
"Enemy siege towers approaching!"
No choice. Time for new tactic. Hide cannon no longer.
"Fine. Prepare cannons!"
"Yes, General!"
Soon cannons on ramparts. Gunners loaded powder, balls, fuses.
Loaded cannons ready.
"Target siege towers! Fire!"
Hiss—BOOM!
Iron balls from Hamsinjin hammered Mongol towers mercilessly. Approaching siege engines crumbled.
"What! What's flying from the walls?!"
Iron barrage smashed towers, crushing nearby troops.
"Iron balls from the walls!"
Iron balls? Salitai thought Goryeo gunpowder-less. Mongols adopted post-Jin conquest; Goryeo impossible. From afar, assumed catapult-like.
"Damn, fire arrows fail, tunneling fails—what's this Kim Gyeongson? Mocking me, the Khan's proxy?!"
Inexperienced general holds? Hamsinjin easy target.
"Commander! We're falling back again!"
"Not an easy fight!"
Indeed. Troops retreating once more. How? Tiny peninsula state, mere Jin vassal ravaged by Mongols.
"What is this Goryeo?!"
Salitai fumed. Could take Hamsinjin, but heavy losses. Destroying siege gear. Delay lets Goryeo prepare rear.
"Commander, bypass Hamsinjin and head south!"
"Bypass first fort?!"
First battle can't flop. Mongol army losing to Goryeo? Battle loss possible, but first one? No.
Better take it with losses. Walls crumbling.
But then, shaking news.
"Commander! Scouts report 100,000 Goryeo troops marching north from Gaegyeong!"
South scouts' report stunned Salitai.
"What?! 100,000? This speck of a country has 100,000?!"
Unaware Goryeo fielded 200-300,000 vs. Khitan, 100,000 shocked him. Assumed ragtag militia.
"Head south!"
100,000. Yes. With coerced Dongjin troops via Po Seonmang, still 30,000. 3:1 edge even generously. Foes infantry-heavy. His battle-hardened vs. theirs. Hamsinjin elites to deter invasion. Goryeo mustered all here. 100,000 means pitched battle, not defense.
Crush them? At Yahu Ridge, Mongols beat 350,000 Jin with 100,000—including 150,000 ironclad cavalry. Goryeo cavalry max 10,000; infantry-mixed 100,000 no match.
"Daring pitched battle vs. Mongol army?"
Not elites—scraped militia. Arrogant guess. Goryeo drilled relentlessly with iron cannon wagon forts; 10,000+ cavalry trained Jurchen-style, superior. Even elites, peninsula fighters vs. steppe-hardened Mongols? No contest.
"Bypass south, smash main army. Straight to Gaegyeong—can they hold?"
Yes. Not bad plan.