It was snowing in the high passes. The Altai mountains were further west than most of the families had ever travelled. Only the Turkic tribes, the Uighurs and the Uriankhai, knew them well and then as a place to avoid, a place of poor hunting and death in the winter.

      Though the mounted warriors could have crossed the range in a single day, the heavily laden carts were ponderous, built for grassy plains and ill-suited to deep snow drifts and goat paths. Tsubodai’s new spoked wheels did better than the solid discs that broke too easily, but only a few carts had been converted and progress was slow. Every day there seemed to be some new obstacle and there were times when the slopes were so steep that the carts had to be lowered on ropes, held by teams of straining warriors. When the air was at its thinnest and men and animals grew exhausted, they were lucky to make five miles in a day. Every peak was followed by a twisting valley and another dogged climb to the best way through. The range seemed to go on endlessly and the families huddled miserably in their furs, exposed to the wind. When they halted, the rush to raise gers before sunset was hampered by frozen fingers. Almost all the people slept under the carts each night, covered in blankets and surrounded by the warm bodies of goats and sheep tethered to the wheels. Goats had to be killed to feed them and the vast herds dwindled as they travelled.

      Thirty days out from the river Orkhon, Genghis called a halt early in the day. The clouds had come down so low that they touched the peaks around them. Snow had begun to fall as the tribes made a temporary camp in the lee of a vast cliff, soaring into whiteness above their heads. There was at least some protection from the biting wind in that place and Genghis gave the order rather than take them over an exposed ridge that would see them still travelling as the light faded. He had riders out for a hundred miles and more ahead of them, a stream of young warriors who scouted the best path through and reported on anything they found. The mountains marked the end of the world Genghis knew, and as he watched his servants kill a young goat, he wondered how Arab cities would look. Would they resemble Chin fortresses of stone? Ahead of the scouts, he had sent spies to learn what they could of the markets and defences. Anything could be useful in the campaign to come. The first ones out were beginning to return to him, exhausted and hungry. He had the beginnings of a picture in his head, but it was still in fragments.

      His brothers sat with him in the khan’s ger on its cart, above the heads of all the others. Looking out into the whiteness, Genghis could see gers like a host of pale shells, thin trails of smoke rising from them to the skies. It was a cold and hostile place, but he was not discouraged. His nation had no use for cities, and the life of the tribes went on all around him, from feuds and friendship to family celebrations and weddings. They did not have to stop to live: life went on regardless.

      Genghis rubbed his hands together, blowing into them as he watched his Chin servants make a cut in the kid goat’s chest before reaching in and squeezing the main vein around the heart. The goat stopped kicking and they began to skin it expertly. Every piece would be used and the skin would wrap one of his young children against the winter cold. Genghis watched as the servants emptied the stomach onto the ground, shoving out a mulch of half-digested grass. Roasting the flesh inside the flaccid white bag was faster than the slow boil the tribes preferred. The meat would be tough and hard on the teeth, but in such cold it was important to eat quickly and take strength. At the thought, Genghis tested the stump he had broken in his drunken ride to Jelme and winced. It hurt constantly and he thought he might have to get Kokchu to pull the root out. His mood grew sour at the prospect.

      ‘They’ll have it on the fire in a little while,’ Genghis said to his brothers.

      ‘Not soon enough for me,’ Khasar replied. ‘I haven’t eaten since dawn.’ Around them in the pass, thousands of hot meals were being prepared. The animals themselves would get barely a handful of dry grass, but there was no help for it. Over the constant bleating, they could all hear the sounds and chatter of their people and, despite the cold, there was contentment in it. They rode to war and the mood was light in the camp.

      In the distance, the generals heard a thin cheering and they looked at Kachiun, who usually knew everything that went on in the gers. Under the stares of his brothers, he shrugged.

      ‘Yao Shu is training the young warriors,’ he said.

      Temuge tutted under his breath, but Kachiun ignored him. It was no secret that Temuge disliked the Buddhist monk he and Khasar had brought back from Chin lands. Though Yao Shu was ever courteous, he had fallen out with the shaman, Kokchu, when Temuge had been his most willing disciple. Perhaps because of those memories, Temuge regarded him with irritation, especially when he preached his weak Buddhist faith to fighting men. Genghis had ignored Temuge’s protests, seeing only jealousy for a holy man who could fight better with his hands and feet than most men with swords.

      They listened as another cheer went up, louder this time, as if more men had gathered to watch. The women would be preparing food in the camp, but it was common enough for the men to wrestle or train when the gers were up. In the high passes, it was often