‘You have incredible luck,’ Genghis said.

The man cried out as he tried to move and he too stared up at the walls above his head.

‘It does not… feel like luck,’ he replied.

Genghis grinned at him.

‘Get him to a healer, Khasar. When his wounds are bound, give him a good mare and whatever else he wants.’

More men could be seen now on the walls as they stared and leaned out, some of them almost as far as the man who now lay at Genghis’ feet.

‘When the city falls, you will know how lucky you truly are,’ the khan said in his own tongue. The man looked blankly at him as Khasar dismounted to help him into the saddle.

The walls of Herat slumped and fell in the sixth month of the siege. One of the towers collapsed with the section, crashing to the rocks below and leaving a gaping hole into the city. The tumans gathered quickly, but there was no resistance. As they entered Herat, they found the streets and buildings already choked with the dead and dying. Those who still lived were brought out onto the plain and made to kneel for binding. That task alone took many days as the fortress had been packed with men, women and children. Temuge gave his servants the task of numbering the prisoners on wax slates, putting the total at a hundred and sixty-three thousand, with almost half as many dying of thirst or hunger in the siege. In their fear and despair, they cried and moaned as they were bound for execution, the sound travelling far across the gers. The warriors of the khan searched every room, hall and basement of the city until it was just an empty shell filled with the dead. The smell of a city after a siege was like nothing else and even hardened warriors gagged as they brought out rotting bodies.

It was sunset by the time Temuge was satisfied with his tally and Genghis decreed the killing would begin at dawn. He retired to the khan’s ger to eat and sleep, but his wife Chakahai sought him out as the darkness gathered. At first, she said nothing and he welcomed her presence. She worked the iron stove, making tea and heating pouches of unleavened bread, mutton and herbs that she had prepared that morning. He did not see the strain she hid from him, though as she passed him a plate of the pouches, he took her hand and felt her quiver.

‘What is it?’ he asked.

She bowed her head. She knew he would respond best to bluntness, but her heart beat so quickly that she could barely breathe. She knelt before him and he put aside his hunger, intrigued.

‘Husband, I have a favour to ask,’ she said.

Genghis reached out and took her hand in his.

‘Ask, then,’ he replied.

Chakahai forced herself to take a slow breath.

‘The women and children,’ she said. ‘Let them go free. They will take word of the city falling. They…’

‘I do not want to speak of this tonight,’ Genghis snapped, letting her hand fall.

‘Husband,’ she said, begging. ‘I can hear them crying out.’

He had listened when she held the key to Kokchu’s treachery. He had listened when she urged him to name Ogedai as heir. Her eyes implored him.

Genghis growled deep in his throat, suddenly furious with her.

‘You cannot understand, Chakahai,’ he said. She raised her head and he saw her eyes were bright with tears. Despite himself, he went on.

‘I take no pleasure in it,’ he said. ‘But I can make this killing a shout that will spread further than I can ride. Word will go out from here, Chakahai, as fast as any bird. They will say I slaughtered every living thing in Herat, that my vengeance was terrible. My name alone will bring fear to those who would stand against me.’

‘Just the men…’ Chakahai began.

Genghis snorted.

‘Men always die in war. Their kings expect it. I want them to know that if they resist me, they are putting their hand in the mouth of a wolf. They will lose everything and they can expect no mercy.’ He reached out once more and took her face in his hand, so she could feel the hard callus of his palm.

‘It is good that you weep for them, Chakahai. I would expect it from a wife of mine and a mother to my children. But there will be blood tomorrow, so that I do not have to do it again, a hundred times and more. These Arabs do not send me tribute because they recognise my right to rule. They bow their heads because if they do not, I will visit fury on them and see all they love turned to ashes.’

Tears streamed from her and Genghis stroked her cheek gently.

‘I would like to give you what you want, Chakahai. Yet if I did, there would be another city next year and a dozen more after that. This is a hard land and the people are used to death. If I am to rule them, they must know that to face me is to be destroyed. They must be afraid, Chakahai. It is the only way.’

She did not reply and Genghis found himself suddenly aroused by her tear-stained face. He put the plate of food on the floor of the ger for the morning and lifted her onto the low bed beside him, feeling his shoulder creak. She shuddered as his mouth found hers and he did not know if it was from lust or fear.

At dawn, Genghis left Chakahai in the ger and went out to watch the killing. He had given the task to the tumans of his sons Ogedai and Tolui. Twenty thousand warriors had cleaned and sharpened their swords for the work, but even so many would be exhausted by the time it was done.

The prisoners sat huddled together in the morning shadow of the broken city as the tumans surrounded them. Many of them prayed aloud and those who faced the grim warriors held out their hands and screamed until the blades fell. It was not quick. The warriors moved amongst them and had to bring the swords down many times as the prisoners writhed in their bonds and struggled to get away. Men and women clambered over each other and the warriors were drenched in blood. Many of the blades were ruined on bone, the steel edges cracked or bent. Noon came and the killing went on, the smell of blood strong in the still air. Warriors left the mass of living and dead, gasping as they drank warm, sour water before walking in again.

The afternoon sun was powerful as they finished at last and the plain fell silent. The tumans of Genghis’ sons were staggering with weariness, as if they had fought a long and bitter battle. Their officers sent them to the river to wash away the blood and clean and oil their weapons. The city stood silent above them, empty of all life.

The man who had fallen from the walls had wept for part of the day, though his tears dried quickly in the heat until he sobbed drily and no more came. His broken ankle had been splinted and he was given a horse and supplies by a nameless Mongol officer, following the orders of the khan. The man rode away as the flies and birds gathered above Herat. Genghis watched him go, knowing he would take the news to all those who had ears to hear.

Genghis thought of Chakahai’s tears as he stood in the shadow of Herat. He had not told her where he would take the nation. The families knew he intended to go home, but one other place had long ceased to send tribute and he would take his army there before he saw those hills and rivers again. Xi Xia was where he had first met the pale daughter of a king, the region a stepping stone that had led him to an emperor’s capital. Like the elders of Herat and Balkh, Chakahai’s father had thought the khan would not survive the Arab armies sent against him.

Genghis smiled lightly to himself as he gave orders for the nation to break camp at last. He had been too long away from the Chin lands and Xi Xia would be the bloody example to bring them to heel.