The ford crossing confirmed what Batu had expected.
Two sections, perhaps a hundred riders total, were already moving off the northern bank and onto the southern track. They pressed toward the channel mouth behind the forward screen that had entered the narrows first.
Behind them, the head of the main column compressed along the road. Riders kept pushing forward because the men behind them had nowhere else to go.
The threshold had been reached.
Batu looked down toward Torghul's signal rider waiting on the eastern wall below him. He raised one hand once.
The rider turned immediately and went.
Kirsa's hundred and fifty-seven riders appeared over the eastern crest in a line that stretched nearly the full width of the upper slope. They descended at a controlled pace, maintaining interval from the ridgeline down toward the base of the passage.
Anyone inside the channel would be able to see them for the entire descent.
That was the point.
At the same time, along the western base, Chaidu's riders rounded the lower edge in a tighter formation, moving to close the opposite side.
Along both ridgelines, tumen warriors rose into view.
The passage stopped looking open and became an enclosed position before Siban's forward screen had time to send a proper report back up the line.
From above, Batu watched the reaction at the ford.
The main body halted almost at once. Riders who had already crossed pulled their mounts up hard. The front of the column compressed against itself while the rear continued pressing forward for several moments before the movement finally died.
Good, Batu thought. Siban was reading the situation quickly.
That meant the next move would come before the encirclement fully closed.
It did.
A formed body separated from the front ranks of Siban's main force and drove directly into the channel mouth behind the riders already inside. Several hundred horsemen entered at speed, maintaining formation despite the confined terrain.
Siban had identified the southern exit almost immediately.
The conclusion itself wasn't wrong.
Guyuk's network had provided Siban with the geographic picture beforehand. The ford conditions. The seasonal water levels. The likely movement paths through the narrows.
But the network had gone dark before Batu's forces established the trap inside the passage.
Now Siban was rebuilding the picture in real time.
Below, the force assigned to the channel floor continued withdrawing south exactly as planned.
Argun POV
The narrows walls pressed close on both sides, and the sound inside the passage became something else entirely.
Argun rode south with the controlled withdrawal, keeping pace with the rest of the formation as it pulled back through the narrow floor of the cut.
Around him, the line held together properly. No rider broke formation to rush for the southern exit. That discipline was key now. If the withdrawal lost cohesion inside the narrows, the entire plan would fail.
Ahead, the southern opening showed itself as a narrow strip of pale afternoon light between the rock faces.
Then he heard the sound behind them.
Several hundred horses moving at speed through a confined stone channel created a different noise than cavalry on open ground. The walls caught the impact of hooves and threw it back doubled. The result was a constant rolling percussion that seemed to come from inside the rock itself.
It came from the north.
It was close.
And it wasn't slowing.
Siban's riders burst through the channel mouth at a canter. They saw the withdrawing formation ahead and immediately continued the charge.
No hesitation.
An order to hold came from somewhere to Argun's left.
He hauled his horse around. The animal resisted the sudden reversal, hooves scraping across the stone floor as it fought for footing.
Around him, the formation folded inward, trying to form a proper defensive line before impact reached them.
There wasn't enough time.
The first riders slammed into the forming position before spacing had fully closed.
One of Siban's horses crashed into the center of the line. The horse beside Argun absorbed the impact sideways, and both animals staggered violently.
The rider to Argun's left caught part of the collision across his right knee. Argun heard the grinding compression of flesh before he properly saw it.
The man made a short, flat sound through his teeth.
His knee had dislocated completely.
The rider reached down with his free hand, touched the joint once, understood the wound immediately, then looked forward again and removed his hand without another word.
No time to deal with it.
Argun already had his saber out, but the space inside the channel was too narrow for full cuts. Horses pressed shoulder to shoulder. Men locked together at arm's length. The walls stood perhaps ten meters away on either side.
So he adjusted.
Instead of swinging, he drove the blade forward beneath the armored coat of the nearest rider forcing into the line. The point punched into the man's ribs.
The rider folded sideways over his horse's neck.
Something flashed past Argun's face. An arrow from deeper in the crush passed between him and the wounded rider beside him, then cracked against the channel wall.
Stone fragments burst outward.
One piece struck Argun across the cheek with a hot sting.
He blinked through it and held position.
More of Siban's riders poured through the entrance behind the first wave, deepening the pressure against the line. Dust rose from the channel floor in a pale column beneath the afternoon light overhead.
Five meters in any direction became impossible to read clearly.
There were only shadows pressing into other shadows. Horses colliding. Men shouting. Steel finding armor, flesh, or bone.
Still, the line held.
It bent under the pressure but did not retreat.
Somewhere farther south, the deeper blocking position was still tightening its spacing. Argun didn't know that. The plan had never required him to know it.
His task was simpler.
Hold the ground in front of him long enough for the rest of the formation to finish closing.
So he held it.
Batu POV
Batu tracked three developments at once.
First, the southern depth position was holding, but it was absorbing more pressure than intended. Torghul had moved to the western base and was directing an improvised reinforcement effort there, pulling two sections away from the western ridgeline coverage to strengthen the deeper line.
That created the second problem.
Chaidu's western position had thinned.
Siban's riders outside the entrance recognized the weakness almost immediately.
Several hundred cavalrymen drove hard against the lower western section, concentrating pressure against the reduced formation. Chaidu's rebuilt contingent now held the approach with only sixty-one riders against a force perhaps four or five times larger.
The plan was beginning to rely on friction instead of reserve strength.
From above, Batu watched the western line absorb the impact.
One rider near the outer left crumpled in the saddle. His horse stumbled sideways, threatening to open a gap in the formation.
The riders beside him shifted immediately, compressing inward before Siban's force could exploit the opening.
Another gap tried to form.
It closed.
Another.
Closed again.
Batu turned his attention east.
Kirsa's line had descended three-quarters of the slope.
If Batu pulled riders from the eastern wall to reinforce Chaidu, the eastern encirclement would open before completion. The ridgeline warriors couldn't abandon the crest without giving the trapped riders inside the channel a route upward.
That meant Chaidu had to survive with the force already in place.
A rider climbed the eastern slope toward Batu from Torghul's position below.
"The depth's holding," the messenger reported. "They haven't broken through."
"The western base?"
"Torghul knows."
The rider turned and descended again without waiting for further instruction.
Good. Batu didn't need to redirect him.
The eastern formation finally reached the lower slope.
Kirsa's riders moved onto the flat ground at the eastern foot of the channel and pushed inward, sealing the base of the cut. The line now extended continuously from crest to channel floor on the eastern side.
Inside the narrows, Siban's forward screen and riders found themselves trapped between two descending ridgelines, a contested southern exit, and sheer stone on both sides.
The sound inside the passage became immense.
Thousands of horses compressed into a corridor barely two hundred meters wide. Pressure from both ridges. Constant collision at the base. Every section fighting to hold ground while more riders forced inward from behind.
Then Batu saw another movement.
Part of Siban's external force peeled away from the western pressure and swept south around the outskirts of the entrance. Several hundred riders accelerated across the open ground near the southern end of the narrows, attempting to strike the depth position from the flank.
A good adaptation.
But Torghul saw it too.
The improvised depth sections wheeled left and intercepted before the flanking arc could fully develop. The attacking riders expected to hit an exposed side.
Instead they collided with a formed line on open steppe.
The maneuver changed instantly from a flanking attack into a frontal engagement against prepared tumen strength south of the narrows, exactly where Batu had wanted the collision to occur.
Siban's riders hit the line at close range.
The momentum stopped there.
Now the shape of the battlefield settled into place.
Chaidu's contingent still held the western base.
The southern exit remained closed by the main tumen body.
The heights showed full rider coverage across both ridgelines.
And inside the cut, Siban's committed force had become completely separated from the larger body outside by the full length of the passage itself.
The encirclement was complete.
The riders trapped inside the narrows were locked between the ridges. The riders outside remained pinned on the flat ground beyond the entrance.
The two halves of Siban's force could still see one another through the length of the channel, separated by little more than the width of the ford road.
But there was no clear path through anymore.
Somewhere inside the compressed mass of riders near the channel mouth, Siban would already be rethinking the situation, testing every remaining possibility against the terrain and the closing riders around him.