Kachiun’s face was stern, but he understood the khan’s dilemma.

‘It is almost twenty miles to Otrar, lord khan. I would have them make the journey on foot, before dark.’ He looked at the sun, judging the time. ‘If they cannot, perhaps they are not fit to lead their men.’

Genghis breathed out slowly in relief he could not show. It would do. The sun was merciless and such a run could kill a man, but they were young and strong and it would serve as a punishment.

‘I will be there to watch you come in,’ he said to the dumbfounded pair. Chagatai glared at Kachiun for the suggestion, but as he opened his mouth to object, Genghis reached down and picked him up in one smooth motion. His father’s fist rested just under his chin as he spoke again.

‘Remove your armour and go,’ he said. ‘If I see you fighting again, I will make Ogedai my heir. Do you understand?’

Both brothers nodded and Genghis stared at Jochi, incensed that he had thought the words were also for him. His temper flared again, but Kachiun deliberately chose that moment to call the men into ranks for the ride to Otrar and Genghis let Chagatai go.

For the benefit of all those who could hear and repeat the words a thousand times, Kachiun forced a smile as Jochi and Chagatai began to run in the vicious heat.

‘You won such a race when we were boys, I remember.’

Genghis shook his head irritably.

‘What does that matter? It was long ago. Have Khasar bring the families back to Otrar. I have debts to settle there.’

Shah Ala-ud-Din Mohammed reined in as he saw the thin trails of cooking smoke rising from the Mongol camp. He had ridden slowly east, covering many miles since the first grey light of predawn. As the sun rose to burn off the morning mist, he stared at the filthy gers of the Mongol families. For an instant, the urge to ride among the women and children with his sword was overwhelming. If he had known the khan had left them so vulnerable, he would have sent twenty thousand to kill them all. The shah clenched his fists in frustration as the light grew. Warriors clustered on the edges, the heads of their ponies peacefully snuffling the dusty ground for grass. For once, there were no warning horns blown from the cursed Mongol scouts.

With a snarl, the shah began to turn his mount away from the camp. They bred like lice, these Mongols, and he had only his precious four hundred to see him safe. The sun was rising and his guards would soon be seen.

One of his men shouted something and Ala-ud-Din turned his head. The sun’s light revealed what the shadows had hidden and he grinned suddenly, his mood lifting. The warriors were no more than straw dummies tied to the horses. The shah strained his eyes as the light grew, but he could not see a single armed man. Around him, the news spread and the noble sons laughed and pointed, already loosening their swords in the scabbards. They had all taken part in punishment raids on villages, when the taxes had been late. The sport was good in such places and the desire for revenge was strong.

Jelaudin did not share the men’s laughter as he rode to his father.

‘Would you have the men waste half a day here with our enemies so close?’

In response, his father drew a curved sword. The shah glanced at the sun.

‘This khan must be taught the price of his arrogance, Jelaudin. Kill the children and burn what you can.’

Slowly, almost ritually, Chakahai wrapped her hand in a length of silk, tying it to the hilt of a long dagger. Borte had told her to beware of the shock of impact, that a woman’s hand could be jarred loose, or sweat enough to slip. The process of winding the silk around her fingers and biting one end to hold a knot was somehow calming as she looked out through the gers at the shah’s riders. The knot of terror in her stomach was not under her control.

She, Borte and Hoelun had done what they could to prepare the camp. They had been given little warning and the more elaborate traps were still unset. At least they had weapons and Chakahai murmured a Buddhist death prayer as she readied herself. The morning was cold, though the air seemed heavy and promised another day of heat. She had hidden her children as best she could in the ger. They lay in perfect silence under piles of blankets. With a vast effort, Chakahai put her fear for them aside, leaving it in a separate place so that her mind was clear. Some things were fate, what the Indian Buddhists called karma. Perhaps all the women and children would be killed that day; she could not know. All she desired was the chance to kill a man for the first time, to fulfil her duty to her husband and her children.

Her bound right hand was shaking as she raised the blade, but she enjoyed the feeling of holding the weapon and took strength from it. Genghis would avenge her, she knew. Unless he too had been killed. That was the thought she tried most to crush as it reared in her mind. How else could Arabs have come to the camp if not over a dead nation and the body of her husband? If Genghis still lived, he would surely have moved mountains to protect the camp. For a Mongol, the families were everything. Yet there was no sign of the khan on the horizon and Chakahai struggled against despair, seeking a calm that came and went in flashes.

At the last, she took a deep breath and felt her heart settle to a slow, heavy thump, her limbs strangely cold as if her blood had chilled in her veins. The riders were trotting towards the city of gers. Life was just a restless fever dream, a short breath between longer sleep. She would reawaken and be reborn without the agony of memory. That at least was a blessing.

The herds of Mongol ponies stirred nervously as the shah rode in with his men. He could see ripples running through the animals and, in the strange silence, he felt a sense of foreboding. He looked to the others to see if they too had a premonition of danger, but they were blindly eager for the hunt and leaned forward in their saddles.

Ahead, threads of cooking smoke lifted lazily into air. It was already growing warm and the shah felt sweat trickle down his back as he reached the first gers. His guards spread themselves into a wide line as they rode into the maze and the shah felt his nerves tighten. The Mongol homes were high enough to conceal anything behind them. Even a mounted man could not see what lay beyond the next, and that made him uneasy.

The camp seemed deserted. If not for the cooking fires, Ala-ud-Din might have thought the place empty of life. He had intended to ride through in one great sweep, killing anyone who ran across his path. Instead, the lanes and paths were silent and the Arab horses drove deeper and deeper without seeing a living soul. Far above his head, an eagle circled, its head twitching back and forth as it searched for prey.

He had not appreciated the sheer size of the Mongol encampment. Perhaps twenty thousand gers were in that place, or even more, a true city sprung from nothing in the wilderness. They had claimed the land on the banks of a nearby river and Ala-ud-Din could see drying fish tied to racks of wood as he passed. Even the flies were quiet. He shrugged to himself, trying to throw off the dark mood. Already some of his men were dismounting to enter the gers. He had heard the older men talk of threatening the children to make the women more pliable. The shah sighed in irritation. Perhaps Jelaudin had been right. Once they were in the gers, the morning would be lost. The Mongols could not be far behind and he did not intend to be caught in that desolate place. For the first time, he wished he had simply ridden past the camp.

Ala-ud-Din watched as one of his son’s friends ducked low to push open the door to a ger. The entrance was almost too small for his massive shoulders. The Arab soldier stuck his bearded face through the opening, squinting into the gloom. Ala-ud-Din blinked as the man suddenly shuddered, his legs quivering as if he had begun a fit. To his astonishment, the soldier dropped to his knees, then fell flat into the ger, his body still twitching.