The river by the town was less than a mile away when the Mongols gave up the running fight and raced for the bridge. Jelaudin galloped after them with his men, intent on their deaths. He had seen them ride in triumph too many times not to take pleasure from the sight. He rode lightly, the breeze cool on his face.

The Mongols did not stop at the bridge. The surviving warriors galloped across without slowing down, risking their lives in the crush of men. It was well done and Jelaudin’s men did not hesitate to follow them.

Jelaudin saw Mongol warriors leap from their horses and take axes to the ropes and timbers of the bridge, ignoring those who rode them down. Perhaps a hundred of his mounted men had crossed and, with terrible clarity, Jelaudin saw that the Mongols intended to cut the force in half, leaving those on the fortress side helpless while they turned on the rest like mad dogs. The sight of such calm thinking broke through his frenzy and he reined in. He could direct his men to kill those who hacked at the bridge supports. If it held, he would destroy the Mongol forces to the last man, but if it fell, many of his men would die. He had done enough, he thought. He had wounded and bloodied an enemy who had not known defeat before. He took a horn from his waist, where it hung on a strap. It had once belonged to a Mongol scout, but his men were ready for the blaring note.

Those who had not yet reached the bridge turned back and formed into shining ranks, already cheering the victory. Those who had already gone over pulled away from the enemy and started to retreat across the river. Jelaudin watched with pride as they followed his orders without question, raising their shields to take the arrows that sailed after them.

The bridge fell, slapping into the river in a great spray. Perhaps fifty of his men were still on the other side and Jelaudin rode to the edge, looking down into the waters. It was too deep, he thought. Perhaps the men could have swum their horses across on another day, but not with enemy archers ready to rush them as they forced their mounts down the banks. Jelaudin raised his sword in salute to those who watched him from across the river, enemy and friend alike.

His men returned the gesture and turned their horses back, riding into the Mongols in one last charge. They were cut down, though each man went without fear, killing as many as he could.

The two forces faced each other across the torrent, panting and bloodied. Jelaudin could hardly describe the ecstasy of the moment. He saw the Mongol officer trot his mount to the opposite bank and, for a moment, they stared at each other. The Mongol shrugged at the trail of dead leading to the fortress in the distance. He raised his sword then, copying the gesture of respect before wheeling his mount and riding away. Genghis would hear and the subdued officer did not have to utter threats on his behalf.

‘The news is in the mouth of every city, Genghis,’ Kachiun said bitterly. ‘Before now, they saw us as unbeatable. This is a crack in that belief, brother. If we let it go unanswered, even for a season, they will grow in confidence and more will come to Jelaudin’s banners.’

‘One successful raid does not make a general, Kachiun. I will wait for Tsubodai to return.’ Genghis gestured irritably to the open plain he had found, eighty miles south of the lake where Kublai and Mongke had learned to swim. The nation could not remain anywhere for long. Lush grass was hard to find in Arab lands, but the world was large and Genghis had two sites picked out to move to in another month. That was simply the way of their lives and he did not think of it beyond quick decisions when the time came. Kachiun’s voice irritated him, interrupting his thoughts of Jochi and Tsubodai. It was true that Jelaudin’s army had killed more than a thousand of his men, the event sending ripples of disquiet through the Arab cities. The first tribute due from the Afghan city of Herat had not come and Genghis wondered if it was delayed or whether they had decided to wait and see what he would do.

Kachiun waited, but when Genghis said nothing, he spoke again, his voice hard.

‘The men lost were from my tuman, Genghis. Let me at least ride to the area and make this bastard prince nervous. If you won’t give me the army, let me raid his lines, striking and vanishing in the night as we have done before.’

‘You should not fear these farmers, brother. I will deal with them when I know that Tsubodai has found Jochi.’

Kachiun held himself still, biting back the questions he wanted to ask. Genghis had not shared Tsubodai’s orders with him and he would not beg to be told, though he wanted very much to know. He still found it difficult to believe that Jochi had taken his men away and tried to lose himself. The spirits knew Jochi had been provoked, and at times Kachiun could only curse the blindness of the father that had led to it, but the reality of betrayal had stunned them all. No one had ever turned against the man who had made the nation. For all his faults, Genghis was revered and Kachiun could hardly imagine the strength of will that allowed Jochi to wrench apart from everything he had known. He saw Genghis set his jaw obstinately, guessing at his thoughts as Kachiun tried again to make him understand.

‘You are the one who built an empire in this place, Genghis, instead of just ruins. You put Arslan into Samarkand and Chen Yi into Merv when he came. They rule in your name, just as kings and shahs ruled before them in those places. Yet they are still invaders and there will always be those who want to see them torn out. Give these Arabs one glimpse of weakness and we will have rebellions in every place we have taken.’ He sighed. ‘I am too old to do it all again, brother.’

Genghis blinked slowly and Kachiun did not know if he was truly listening or not. The khan seemed utterly obsessed with the son who had turned against him, perhaps because no one else ever had. Each day he would scour the horizon for some sign of Tsubodai. It was too soon, Kachiun knew. Even if Tsubodai had ridden as fast as light scouts, he would hardly have reached the northern land where Jochi had hidden himself. Once more, Kachiun itched to know what Tsubodai had been told to do. He suspected he knew and pitied Tsubodai for the task. Kachiun was aware that Tsubodai thought of Jochi almost as a son. It was typical of Genghis that he should test the man’s loyalty to breaking point by sending him. His brother had always been ruthless with those around him, as well as himself.

Kachiun prepared to try once more, desperate to have Genghis understand. He swallowed drily, realising he could have used Tsubodai then. His brother listened to Tsubodai above all others and he would not delay here while the cracks appeared in everything they had built.

‘They countered horns, Genghis, swinging out around them. They have shields as good as any we have seen and armoured horses that survive our arrows. It is not the numbers I fear, brother, but the way this Jelaudin uses them. If you will not come, let me send them back on their heels. They will not surprise my tuman with the same tactics. We will counter them and send a message to anyone who imagines we can be defeated.’

Genghis opened his mouth to suck at one of his back teeth.

‘Do as you will, Kachiun,’ he said, then thought better of leaving his brother with complete authority to act. ‘Take three tumans, your own and two others. Not Ogedai or Tolui. Their men are still fresh from the teat and I do not want them with you.’

Kachiun spoke quickly.

‘Jelme then, and Khasar.’

Genghis nodded, still staring into the north, where his thoughts rested with Tsubodai.

‘Skirmish, Kachiun, do you understand? If they are as terrible as I have heard, I do not want you to lose your men in the mountains. Bleed them a little, as you have done before, as you did at Yenking and against the shah. I will come with Tsubodai.’