"The city will be desperate for them to get through," Kachiun said over the hacking sound. "I wonder if we will regret sending half our men away?"

Genghis shook his head mutely before pulling in a clean breath at last. He strode past Kachiun to the door and spat a wad of phlegm on the ground, wincing as he tried to clear his throat.

"See this," he said hoarsely, picking up a Chin crossbow they had captured at the Badger's Mouth. Kachiun followed his brother's gaze to a straw target three hundred yards away along a path. Genghis loosed arrows for hours every day to restore his strength, and he had been fascinated by the mechanisms of the Chin weapons. As Kachiun watched, he took careful aim and pulled the carved trigger, sending a black bolt whipping through the air. It fell short and Kachiun smiled, understanding immediately. Without a word, he picked up one of his brother's bows and selected an arrow from a quiver, drawing it back to his ear before sending it unerringly into the center of the straw shield.

The blood had faded from Genghis's cheeks and he nodded to his brother.

"They will be slow with supplies for the city. Take your men and ride up and down the lines, never close enough for them to reach you. Thin them a little and I will do the rest when they arrive."

As Kachiun galloped through the camp, word from the scouts traveled even faster. Every warrior there was ready in just the few moments it took to race to his pony and grab his weapons from the walls of the gers.

Kachiun shouted orders to his senior officers and they spread the word, halting many men in their tracks. The new form of warfare was still only a veneer over the raiding bands, but the command structure was solid enough for groups of ten to gather and receive their instructions. Many had to return to their gers for another quiver of fifty arrows on Kachiun's order before racing to form up in the great square of ten thousand. Kachiun himself marked the farthest line by riding his pony up and down, a long war banner of gold silk streaming out behind him.

He conferred once more with the scouts who had sighted the relief column and passed the fluttering standard to a messenger in the front rank, a boy of no more than twelve. Kachiun looked along the ranks as they formed and was satisfied. Each man carried two heavy quivers looped over his shoulders. They needed no supplies for a lightning raid and only bows and swords slapped on their thighs and saddles.

"If we let them through to the city," he bellowed, turning his horse in place, "it will take another year to see it fall. Stop them and their mounts and weapons are yours, after the khan's tithe."

Those who could hear roared their appreciation of this, and Kachiun raised his right arm and dropped it, signaling the advance. The lines moved forward in perfect formation, the product of months of training on the plain in front of the city when there were no enemies to fight. Officers shouted orders out of habit, but in fact, there were no flaws in the lines. They had at last thrown reins on their enthusiasm for war, even after so long a wait.

The column had been forty miles south of Yenking when the scouts crossed its path. In the time it had taken Kachiun to return, the slow-moving mass of men and animals had shortened the distance to only twelve. Knowing they had been seen, they had pushed the herds as fast as possible, but there was only so much they could do before they saw the dust cloud of approaching warriors.

The senior officer, Sung Li Sen, hissed under his breath as he saw the enemy for the first time. He had brought almost fifty thousand warriors north and east from Kaifeng to relieve the emperor's city. The column was a massive, ponderous thing, with carts and bullocks stretching back along the road. He squinted at the squares of cavalry guarding his flanks and nodded to their commander over the heads of the men. This was a battle long in coming.

"First position!" he snapped, his command repeated up and down the trudging lines. The orders he had been given were perfectly clear. He would not stop until he reached Yenking. If the enemy engaged him, he was to fight a running battle all the way to the city and avoid being bogged down in skirmishes. He frowned at the thought. He would have preferred a blanket order to crush the tribesmen and worry about resupplying Yenking when they were bones.

All along the vast snake of men, the soldiers raised long pikes like bristles. Crossbows were cocked by the thousand and Sung Li Sen nodded to himself. He saw the lines of Mongol riders more clearly now, and he braced himself in the saddle, aware that his men looked to him for an example of courage. Few of them had ever traveled this far north, and all they knew of these wild tribesmen lay in the emperor's demand for support from his southern cities. Sung Li Sen felt his curiosity swell as the riders split along an invisible line, as if his own column was a spearhead they did not dare approach. He saw that they would pass on either side of him and smiled tightly. It suited his orders that they do so. The road lay open to Yenking and he would not stop.

Kachiun held back the gallop to the last possible moment before leaning into the wind and yelling for his mount to stretch its gait. He loved the thunder that sounded around him as he stood in the stirrups. Over such a distance, they seemed to close slowly, then everything was rushing toward him. His heart pounded as he reached the Chin column and sent his first arrow snapping through the air. He saw the Chin bolts streak out, falling uselessly into the grass. To ride along that endless line was to be untouchable, and Kachiun laughed aloud at the joy of it, sending shaft after shaft. He hardly had to aim with five thousand men on either side of the column, pinching it between them in whipping strikes.

The Chin cavalry hardly managed to reach full gallop before they were annihilated to a man, smashed from their mounts. Kachiun grinned when he saw not one of the enemy horses had been killed. His men were being careful, especially now they had seen how few riders the Chin had brought to the field.

When the cavalry were broken, Kachiun chose his targets with precision, aiming at any officer he could see. Within sixty heartbeats, his tuman loosed a hundred thousand shafts at the column. Despite the lacquered Chin armor, thousands were felled in their tracks, with those behind stumbling over them.

Kachiun could hear the cattle lowing in distress and panic, and to his pleasure, he saw the herd stampede, crushing more than a hundred of the Chin soldiers and breaking a hole in the column before they lumbered off into the distance. He had reached the end of the tail and swung in a little further, ready to double back. Crossbow bolts rattled off his chest, near spent. After the months of tedious training, it was simply wonderful to be riding against an enemy, and better, one who could not touch them but only die. He wished he'd known to bring more quivers. His grasping fingers found the first one empty and began his last fifty shafts, taking a Chin bannerman off his feet with the first.

Kachiun blinked wind-tears out of his eyes. He had thinned the column enough to see through it to the second five thousand on the eastern flank. They too were riding with impunity, striking at will. Another sixty heartbeats and a hundred thousand arrows followed the rest. The Chin soldiers could not hide and the neat column began to disintegrate. Men who trudged near carts threw themselves under them for protection while their colleagues died around them. A great wail of fear went up from the pikemen, and there were no officers left alive to rally them or keep them on the road to Yenking.

Kachiun began his second run, this time too far from the column to waste a shot. The lines reversed with the ease that comes of ceaseless hours of drill, and fresh quivers were emptied quickly. Kachiun galloped flat out along the lines, glancing back at the trail of dead they left behind as the column pushed onwards through the storm. The soldiers had kept their discipline, though the pace was slowing. Other men bawled orders in the place of dead officers, knowing that to panic was to invite complete destruction.