As he took a breath to give orders, Ala-ud-Din caught a movement out of the corner of his eye and brought his sword round in a sweeping blow. A woman had been creeping up on him and the tip caught her across the face, gashing her jaw and breaking teeth. She fell back with blood pouring from her mouth, then to his horror leapt at him and sank a dagger into his thigh. His second blow took her head off cleanly, then the silence shattered into chaos all around him.

The gers erupted and his warriors were instantly fighting for their lives. Ignoring the pain from his wound, the shah spun his horse and used its bulk to shoulder down a woman and young boy who raced towards him, screaming and brandishing heavy knives. His men were veteran cavalry, used to defending their mounts from men on foot. Yet the Mongol women seemed to have no fear of death. They ran in close and cut either the horse or a man’s leg before vanishing behind the nearest ger. Ala-ud-Din saw more than one hacked down, then stagger in before death took them, using their last breath to plunge a blade into flesh.

In heartbeats, every man of his four hundred was fending off more than one, sometimes four or five different women. Horses bolted wildly as their haunches were cut and men cried out in fear as they were pulled from their mounts and stabbed.

The Arab guards held their nerve. More than half of them rode without care to surround the shah and the rest drew into close formation, each man watching for attacks on the others. The women darted at them from the side of every ger, appearing and disappearing like ghosts. The shah felt hemmed in, but he could not ride free and let the khan tell the world he had run from women and children. One ger had collapsed as a horse crashed into it and he saw an iron stove broken open. He snapped an order to his servant, Abbas, watching eagerly as the man tore a great strip of felt and lit it from the scattered fire.

The attacks became more desperate, but his men had the rhythm by then. The shah could see some wild fools had dismounted to rape a young woman on the ground and he rode furiously to them, using his horse to knock them aside.

‘Have you lost your minds?’ he roared. ‘Get up! Up! Fire the gers!’

In the face of his fury, they drew a knife across the throat of the struggling woman and stood, abashed. Abbas already had one ger aflame. The closest guards took up pieces of the burning material in their hands, riding away with them to spread the terror as far as they could. Ala-ud-Din coughed as he breathed in thick grey smoke, but he exulted at the thought of the khan coming back to a field of ashes and the cold dead.

Jelaudin was the first to spot the running boys. They darted through the gers near the river, weaving between paths, but always coming closer. Jelaudin could see hundreds of the devils, running bare-chested with their hair flying. He swallowed nervously when he saw they carried bows, like their fathers. Jelaudin had time to shout a warning to his men and they raised their shields and charged down the paths at this new threat.

The Mongol boys held their ground as the Arabs thundered towards them. Jelaudin’s men heard a high voice shout an order, then the bows bent and arrows were flying in the breeze.

Jelaudin yelled a curse as he saw men knocked down, but it was just a few. The boys were as accurate as the adults, but they did not have the power to batter shafts through armour. The only deaths came from an arrow in the throat and those were good odds. As Jelaudin drew close, the boys scattered before his men, vanishing into the labyrinth. He cursed an arrangement that meant they had to turn only one corner to be lost to view. Perhaps that was how the Mongols had intended it when they laid out their camps.

Jelaudin cantered around a ger and found three boys in a huddle. Two loosed a shot as soon as they saw him, the arrows passing wide. The other took a heartbeat longer and released his shaft just as Jelaudin’s horse crashed into him, shattering the boy’s ribs and tossing him away. Jelaudin roared in pain, looking down in disbelief at the arrow that had ripped along his thigh under the skin. It was not a bad wound, but he raged as he drew his sword and killed the dumbfounded pair before they could react. Another arrow whirred past his head from behind, though when he spun his mount round, he could see no one.

In the distance, smoke rose in thick billows as his father’s men set fires. Already the sparks would be landing on other gers, burying themselves deeply in the dry felt. Jelaudin was completely alone, yet he sensed movement all round him. When he had been a very young boy, he had once been lost in a field of golden wheat, the crop taller than he was. All around him, he had heard the scuttling, whispering movement of rats. The old terror surfaced. He could not bear to be alone in such a place, with creeping danger on all sides. Yet he was not a boy. He roared a challenge to the empty air and hammered along the closest path, heading for his father and where the smoke was thickest.

The shah’s men had killed hundreds of the Mongol women, yet they still came and died. Fewer and fewer of them managed to draw blood from the guards, now that they were prepared. Ala-ud-Din was astonished at their ferocity, as fierce as the men who had ravaged his armies. His sword was bloody and he burned with the need to punish them. He breathed heavy smoke and choked for a moment, delighting in the destruction as the fire spread from ger to ger. The centre of the camp was aflame and his men had developed a new tactic. As they saw a Mongol home burn, they waited outside the door for the inhabitants to come rushing out. Sometimes, the Mongol women and children cut their way through the felt walls, but more and more were slaughtered as they rushed armed and mounted men. Some were already on fire and chose to die on swords rather than burn.

Chakahai ran on bare feet towards a warrior with his back to her. The Arab horse seemed huge as she approached, the man on its back so far above her that she could not see how to hurt him. The crackle of flames hid the sound of her steps as she raced across the grass. Still he did not turn and, as he shouted to another man, she saw he wore a leather tunic decorated in plates of some dark metal. The world slowed as she reached the hindquarters of his mount and he sensed her. He began to turn, moving as if in a dream. Chakahai saw a glimpse of flesh at his waist, between his belt and the leather armour. She darted in without hesitation, ramming the blade upwards as Borte had told her to do. The shock of it thrilled along her arm and the man gasped, his head snapping back so that he stared at the sky. Chakahai yanked the blade and found it had wedged in him, trapped in flesh. She pulled at it in a frenzy and did not dare look at the Arab as he brought his sword arm up to kill her.

The blade came loose and she fell backwards, her arm covered in his blood. The Arab slumped and fell almost beside her, so that for an instant their eyes met. She struck out again in panic, but he was already dead.

She stood then, her chest heaving as she was filled with a dark pleasure. Let them all die in such a way, with their bowels opening and their bladders darkening the ground! She heard galloping hooves and looked up dazedly as another Arab stallion came to smash her from her feet. She could not move in time and the exhilaration of the kill left her, to be replaced by a vast weariness.

Facing the Arab soldier, she saw Yao Shu before he did. The Buddhist monk shot across the face of the horse, aiming a heavy stick at a foreleg. She heard a crack and the animal went down hard. As she watched in a daze, it turned right over in front of her, crushing the man on its back. Chakahai could only stare at the kicking legs, seeing that one of them hung at a vicious angle. She felt Yao Shu’s hands pulling her between gers and then the world came back in a rush and she began to retch weakly.