Forging Gunpowder in Goryeo
To put it simply, preparing the materials for what I'm trying to do isn't all that hard.
"We've gathered them, miss."
"Hm? It's just the family retainers?"
There were about twenty of them—the same guys I'd seen around the Choi household.
"As you instructed, this is a matter of national importance, so it's best to use only the most trustworthy people. Aren't the Choi family's retainers more than enough?"
Fair enough. Gunpowder was top-secret stuff on a national scale. What would the common folk say if they saw this? Better to stick with loyal retainers whose devotion was beyond question.
Getting limestone from the Song was tricky, so niter beds were the way to go.
To make a niter bed—and let me break it down simply—you needed manure, straw, ash, and mud. In other words, compost.
Goryeo already had plenty of compost, human or animal. With Father's support, I secured the land, and the heavy lifting was left to the retainers.
Once you got it going, unlike limited natural saltpeter sources, you could produce it in bulk.
"Miss, why are you doing something like this?"
Several retainers looked puzzled, either dissatisfied or genuinely curious.
"I'll make it worth your while, so can't you help out?"
I put on my pitiful kitten face, and the dozens of retainers Kim Jun had brought softened up after exchanging glances.
"We can't refuse if it's you asking, miss. It's just... we don't get it. Won't this just stink?"
"It's an experiment, so whatever. Just plug your noses."
"So, do we just light it on fire and make it go boom?"
"Hey now, who said anything about killing? I plan to have the smithy make something with it."
The smithies were under state control, but come on—I was the daughter of the Choe regime. What were they gonna do? You had to push boundaries sometimes, even if there was grumbling. Once the results came in, everyone would love it.
In the Goryeo royal palace in Gaegyeong, Emperor Gojong was receiving reports from his eunuchs. Even as a figurehead monarch, he had to keep up appearances or he'd feel ashamed of calling himself a descendant of kings.
"The daughter of the Military Regent Choi U is gathering human and animal manure? And using the smithy?"
"Yes, Your Majesty."
This was the age of the military, sure, but smithies were a national asset. And some girl with no official position was just... doing whatever? There were over ten in Gaegyeong alone.
"What kind of nonsense is this? Fertilizer, maybe?"
"We're not sure, but dozens of able-bodied men have been mobilized. Still, the Military Regent's daughter has always been one for wild talk."
Dozens of men. The Choe family had used retainers to bulldoze commoners' homes before. Typical Choe behavior.
"Figures. I don't know what she's up to, but shouldn't the Military Regent keep his personal whims from his daughter?"
The royals could never voice complaints like this anyway. But this time, it felt excessive. If it was just the Regent spoiling his daughter, he could at least say a word.
A year had passed before I knew it. My body had grown even more womanly, making it awkward to run like a man—the weight up top was a real hindrance. Much as I hated to admit it, I felt my past life's male self fading away bit by bit.
"You could just marry into a good family and live happily loved."
Father still wanted to marry me off. My betrothal to Kim Yakseon hadn't been broken, just postponed. As a Choe family matter, even his side couldn't outright refuse and had accepted the delay.
"Father's saying that again?"
"I'm just worried for you. A woman who's captured the hearts of Gaegyeong's men, refusing marriage to live alone."
No man who could turn me—a reincarnated guy—into a proper woman had appeared. And I doubted one ever would.
Anyway, this was all for the regime. Even a doting father like Choi U couldn't argue with that.
"Hee hee hee. It's all for you and the country, Father."
"Fine, fine. Marrying some stranger, wanting freedom as my daughter—I can give you that much. But..."
"Yes?"
"Playing around with compost? It's unbecoming for the daughter of the Military Regent."
Choi U shook his head with a sigh.
This is all for us, I tell you? For Goryeo's gunpowder office?
"Good news soon, Father."
The puzzle pieces were all in place. By original history's standards, this was cutting-edge tech.
"Miss, palace eunuchs have come by several times. His Majesty knows."
"His Majesty?"
Gojong spying on me?
"Forgive me for saying so, but a young woman with no office using state resources like this... it undermines the imperial dignity."
"They said that outright?"
"They expressed concern."
Pfft, concern. It's a warning.
Their authority was already in the gutter. What more could fall? Classic Goryeo—king abroad, emperor at home. The Myocheong rebellion had pushed for an emperor title and moving the capital to Seogyeong, meaning emperor both domestically and internationally. Not some vassal king play-acting, but equal to Song and Jin.
"If they come, say it's for the imperial house too."
"Really for the imperial house?"
Kim Jun narrowed his eyes like he was about to tattle to Father.
Hey, who'd think I'm a royalist? Why side with illegitimate kings?
Besides, helping Father helped the throne.
"Helping Father helps the throne, right?"
Officially, Father served the emperor, ruling by his authority. Father's achievements were Gojong's. In a monarchy, a vassal's merits became the sovereign's.
Just watch and wait. This gunpowder might let the Wang clan stand equal to the Zhongyuan emperors someday. Though it'd need the military regime's backing—and Gojong, propped up by them, hardly qualified as a true emperor anyway.
"Should we rush before interference?"
Father had sycophant officials, but this could stir attacks on the regime.
Anyway. After long, mocking months, saltpeter was finally ready.
Hired farmers with monthly rice rations—ten seok each—and harvested sulfur near Anseong outside Gaegyeong.
Joseon imported sulfur, but the peninsula had it; low quality and small yields meant reliance on imports. But if we could mine it...
"Can sulfur really produce this much?"
Weirdly, yields were huge. I'd planned for Gangwon-do scale, but Anseong overflowed. Saltpeter too.
Was Joseon underselling it? Nah, even I know better. Piles like mountains—I'd have heard.
"Aigoo, don't make us repeat ourselves. Even a baby could dig it; crumbles at a touch."
The farmers said it was so easy they felt guilty taking extra rice. Some even suspected Choe trickery.
"You sent bandit types to sulfur spots, loaded them with cash—they had to deliver."
"Yeah. Hm. I see."
His face was sincere—no fear-talk.
Sulfur secured, saltpeter from niter beds. Leached with hot water, filtered, boiled to crystallize—just like before. But next was key.
"Is it done?"
Kim Jun eyed the crystals.
"No, dissolve in boiling water now."
Fire risk, so sealed containers later. Dissolve crude saltpeter to minimize insoluble impurities.
"Why melt what we made? Wasn't it hot water already?"
"To purify the dirt inside."
Mix in wood ash to precipitate calcium and magnesium carbonates. Stir 30 minutes to an hour, filter through cloth. Evaporate like initial crystallization. Cool at room temp for pure crystals.
So, just do it.
"Fussy process."
"But it creates niter beds, jobs."
Once gunpowder flowed, Father couldn't dodge scrutiny. Smithy use was royal business; new weapon reports? Needed results to boost authority. This innovation would secure the military regime's future.
Rinse pure product in cold water, dry—done.
"How pure?"
"Most? 2-3 more rounds skyrockets it. Just hire folks."
They earn, I get gunpowder. Win-win.
Couldn't straight-up ask Song for tech—they banned water buffalo horn exports over our bows. No help even if Mongols crushed us.
"How's this a weapon?"
"Needs sulfur and charcoal."
Do I explain everything? Medieval ignorance...
Here, it was basically done. Saltpeter was the hassle.
Now mix ratios right.
"Ground separately as ordered."
Had laborers use iron balls and millstones carefully—fire risk from properties. Wet mix with water or alcohol, dry to cakes, grind fine.
"Labor-intensive."
Kim Jun sweated watching drooping workers.
Mixed the two, birthed gunpowder—a giant leap.
Cast-iron crude cannon named Gupo. Brass for now, but pig iron soon—sulfur abundance helped.
"Will this really work?"
Kim Jun fiddled with unloaded Gupo.
Shut your trap.