She had left in a rush then, gathering her clothes even as he protested the charm was unfinished. He had watched her go almost at a run and his stomach had clenched at what he had dared to do. He did not fear her husband, Palchuk. There were few men who would even dare to speak to the shaman and Kokchu did not doubt he could send the man away. Was he not the khan’s own spirit-talker, the one who had brought Genghis victory after victory?

Kokchu bit his lip at the thought. If Temulun told Genghis her suspicions, of a hand too intimately on her thighs and breasts, no protection in the world would save him. He tried to tell himself she would not. In the cold light of day, she would admit she knew nothing of the spirits, or the manner of calling them. Perhaps he should consider daubing one of the maimed men in the same way, so that the news of the ritual would get back to her. He considered it seriously for a moment, then cursed his lust again, knowing that it had put everything in danger.

Kokchu stood at a crossroads, watching two young women lead ponies by the reins. They bowed their heads as they passed and he acknowledged them graciously. His authority was absolute, he told himself, his secrets safe. Many of the women in the camp would not have men coming home to them. He would have his pick of them then, as he consoled them in their grief.

Before dawn lit the plain, the remains of ten tumans left the ashes of their fires and assembled. Not one was intact and the worst were reduced to just a few thousand men. Those warriors too injured to fight remained at the makeshift camp, bloodied and bandaged, or simply left to die with their companions. The shamans who might stitch and heal them were all far away. Many of them asked for a clean death and were given it with a single blow from a sword, in all honour.

In the gloom, Genghis listened to a tally of the dead as a fresh breeze across the plain made him shiver. He bowed his head at the names of senior men like Samuka and Ho Sa.

There were too many to recite them all. Twenty-three thousand had been killed, maimed or lost in the battles against the shah. It was the worst tally he had ever known and a terrible blow for the nation. Genghis felt a slow rage building whenever he looked for faces and found them missing in the ranks. His sister’s husband, Palchuk, was among the dead and he knew there would be rivers of grief when he returned at last to the camp.

Genghis looked up and down the lines as they formed. As well as his own tuman of ten thousand, he noted the banners of Khasar and Kachiun, Jebe and Tsubodai, Chagatai, Jelme and Jochi. He had given orders for broken tumans to fill the places of the dead and eight tumans had formed out of the ashes. From the youngest boys of fourteen, they were veterans. He knew they would not fail him.

Genghis reached down to touch his lower leg and grimaced at the sick feeling and wetness he found. He had taken the wound the day before, but he could not remember how it had happened. He could not stand on it, but he had tied the foot into the stirrup so that he could still ride. Some of his warriors had lost part of their armour to arrows or sword blows, suffering gashes that they bound with strips of dirty cloth. Others had taken a fever through the wounds and poured with sweat in a dawn breeze that could not cool them. They sat their horses in grim anger, waiting for dawn and first sight of the enemy. No one had slept the night before and they were all bone-tired, but there was no give in them, no weakness. They had all lost friends or relatives. The days of battle had burned away everything but a cold desire to avenge the fallen dead.

When there was enough light to see, Genghis stared out at the shah’s army. He heard distant horns blow an alarm as the shah’s scouts caught sight of the host waiting for them, but the Arabs were sluggish in their movements. The sight of the Mongol army unnerved them and Genghis could see them mill aimlessly, all order gone.

He gave the command to trot and his tumans moved with him. His entire front rank of two thousand men weighed lances in their hands, feeling the strain on tired, torn muscles. The rest readied swords and the distance closed.

Genghis saw two men running out ahead of the forming lines, holding banners of white cloth. He wondered if they meant to surrender, but it did not matter. The time for mercy was long gone. Many of those who had died had been known to him and he had only one answer to give, only one they would approve of if their spirits still saw the world below. The men with white banners were killed as the Mongol line swept past them and a low moan came from the rest as they saw and tried to brace for the charge.

Forty elephants were brought to the front, but Tsubodai ordered his archers to shoot for the legs and sent them rampaging back into the Arab army, causing more destruction than they ever could have against mounted men.

The great line of lances hit almost as one and Genghis shouted the order for horns. His son Chagatai swept forward on the right, while Jochi matched him on the left. The Mongol warriors began the slaughter as the sun rose over the east. They could not be held. They could not be thrown back.

Chagatai’s tuman pinched in against the right flank, their speed and ferocity carrying them to the very centre of the Arabs. In the chaos and noise, there was no calling him back. Jochi’s wing spilled along the left flank, carving dead men out of living lines. Across the battlefield, he saw Chagatai had plunged too far into the mass of terrified men. He could see him only a few hundred paces away before the Arab ranks seemed to swallow him. Jochi cried out. He dug in his heels and led his men like a spear thrust into the jerking body of the Arab army.

The front ranks were hit so hard by Jebe and Tsubodai that they bowed right back in a bloody cup. No one had taken command and in the chaos, the tumans of Chagatai and Jochi sliced through them until the brothers were separated by just a few struggling, panting men.

The Arabs broke, terrified by the khan’s warriors. Thousands threw down their weapons and tried to run, but none of the generals hesitated. Those who turned their backs were cut down without mercy and by noon the army of the shah was a morass of desperate, flailing groups. The slaughter continued without pause. Some of the shah’s men knelt and prayed aloud in shrieking voices until their heads were taken by galloping men. It was butcher’s work, but the Mongols were willing. Many of them broke their swords in huge swings and had to pick up one of the curved sabres that littered the ground. Lances were snapped in Arabs too dazed to step out of the way.

In the end, just a few hundred remained. They had no weapons and held their arms high to show empty palms. Genghis grunted a final order and a line of lancers accelerated. The Arabs cried out in terror, then were silent as the riders rolled over them and returned, dismounting to hack the dead men into small pieces, until their fury and spite were spent.

The Mongol tumans did not cheer the victory. From the first light, there had been no fight in the Arab army, and though they had taken a savage pleasure in the killing, there was no more glory in it than a circle hunt.

The ground was soft with blood as individual warriors looted the dead, cutting fingers for rings and stripping the bodies of good boots and warm clothing. Flies gathered in great swarms, so that the Mongols had to bat them away from where they landed on lips and eyes. The buzzing insects crawled intimately over the dead, already beginning to corrupt in the heat.

Genghis summoned his generals and they came to him, bruised and battered, but with satisfaction in their eyes.