The Trebuchet That Broke a Mountain: Siege of Minerve

Morning sermons going on

"Jesus is the lord and savior of us all. He and he only is the true God. The heretics of Minerve and other towns in southern France think that Jesus was just a pure soul and that the world is evil. They should know that Jesus is fully divine. Not only that, these heretics don't even believe in the authority of the Catholic Church. They've appointed their own leaders called 'Perfect.'"

"You all are hereby granted the title of crusaders. You don't need to go to the Holy Land to earn this honor. Drive these 'Cathars' out of France and the Church shall call you true crusaders."

And just like that, the speeches kept going throughout the crusader army. They were led by Simon de Montfort.

He had laid siege to the fortress of Minerve.

It was one of the most defensible places in the whole region. Built on a cliff 225 meters above the Cesse River. With natural rock walls, thick defenses, and an internal water shaft built deep into the mountain. You couldn't starve them out. They had their own water. They could wait.

The Crusaders had around ten thousand troops. The defenders? Maybe two hundred knights, plus the citizens. But even ten thousand couldn't storm a cliff like this. They couldn't just run up and climb. It was suicide.

"My lord, situation is tense. As you know, most of the crusaders are volunteers. They serve for forty days before returning. This constant rotation is making it hard to maintain pressure. Unlike Acre, we can't keep this siege going for years."

"I know. What about our plan? What about Malvoisine... the trebuchet?"

"The engineers are working, but even once it's ready, it can't hit the fortress walls. They're just too high."

"Then tell them to finish it anyway. I have another idea."

A few days later...

"It's ready, my liege. Malvoisine stands tall. But even with our best effort, we can't reach the wall's height. The trebuchet's power isn't enough to throw stones that high."

"The men are growing impatient. They're not trained soldiers. They're peasants, mercenaries. This siege is draining them. I beg you to consider moving on."

"Silence."

The commander stood, staring at the mountain.

"What makes this place so tough? The walls? The position? Sure. But not as much as that water shaft. As long as they have water, they can wait us out. Months, even years. But what if we destroy their water?"

"But how? We can't even reach the walls..."

"Then we aim higher. Past the walls. We hit the cliff behind the fortress. Their water shaft runs through that rock. Hit it hard enough, it'll break."

"And what do we use to do that?"

"One-ton stones. Find them. And start building."

The engineers stood there, stunned.

One ton... that's a thousand kilograms. You sure you aren't mad, my lord?

"I'm not. Build it. And make sure it flies."

They stared at the rock. It could crush ten men under it. Now they had to launch it uphill.

Not sideways. Not even slightly above. Full uphill.

That's where Minerve sat. Like a lion sitting above the valley, watching quietly.

So the engineers sat down. And they began the math.

"We need to throw this 1000 kg rock at least 200 meters forward and upward. It won't hit the walls. We'll aim behind them. Straight into the cliff."

The trebuchet works on a simple principle. Lever and counterweight. One side is heavy and drops. That energy transfers to the arm, flinging the stone from the other end. (Learn more about how trebuchet physics work against impossible odds in our monster siege story.)

In very basic terms, if you want to throw 1 kg of stone, you need around 12 kg of weight on the other side, plus enough arm length. Just like a tall soldier can throw a spear farther because of longer arm reach. Same principle here.

They scribbled the numbers:

To throw a 1000 kg rock at 35 meters per second, they needed about 612,500 joules of energy.

That meant a counterweight of nearly 12,500 kilograms, falling from 5 meters.

Twelve and a half tons.

That's what they needed to pull this off.

They loaded stones, iron blocks, timber, anything heavy enough. The trebuchet creaked under the weight.

But the numbers were solid.

The math was done.

And math meant war.

"Fire."

The signal came quietly. Just one word.

The ropes snapped. The arm dropped. The trebuchet groaned.

And the rock lifted off.

Not fast. Not light. It rose like a curse. Heavy. Angry.

It climbed. Climbed. Climbed.

Then vanished behind the cliff wall.

A moment of silence.

Then boom.

The ridge shook.

Dust shot out the other side. The engineers leaned forward, blinking.

"Reload."

They launched five more.

By the seventh, they saw it.

A thin stream running down the rocks.

The chief engineer pointed. "That's their water shaft. It's cracked."

Cheers erupted. The trebuchet crew collapsed in exhaustion. But their eyes stayed fixed on the cliff. That thin stream was growing.

Inside Minerve, the panic had started.

Water buckets ran dry. Wells emptied. Cisterns collapsed. They tried plugging the channel, but it was too deep. Too broken.

They held on for two more days.

Then a white flag.

The gates opened. Knights and civilians walked out. No fighting. No bloodshed in the end.

But the mountain had lost.

And the message was clear.

You can build the strongest walls. You can hide on top of a cliff.

But if we break your water...

You break.