'This is why I woke you,' Kachiun replied.

Both men were brothers to the great khan, uncles to the next. They were generals of proven authority, their names known to every warrior who fought for the nation. When they reached the gate, a visible ripple ran through the ranks of men there, vanishing into the darkness. The bondsmen halted around their masters, hands on sword hilts. On both sides, the men were strung as tightly as their bows. Kachiun and Khasar glanced at each other, then dismounted.

They stood on dusty ground, the grass long since worn away by traffic through the gate. Both men felt the sullen gaze of those who faced them. The men at the gate bore no marks of rank, no flags or banners to identify them. For Kachiun and Khasar, it was as if they looked upon the raiders of their youth, with no allegiance to the nation.

'You know me,' Khasar roared suddenly over their heads. 'Who dares to stand in my way?'

The closest men jerked under a voice that could carry across battlefields, but they did not respond, or move.

'I see no signs of tuman or minghaan in your ranks. I see no flags, just dog-meat wanderers with no master.' He paused and glared at them. 'I am General Khasar Borjigin, of the Wolves, of the nation under the great khan. You will answer to me tonight.'

Some of the men shuffled nervously in the lamplight, but they did not flinch from his gaze. Khasar guessed the best part of three hundred men had been sent to close the gate and no doubt it was the same on the other four walls of Karakorum. The bondsmen snarling at his back were outnumbered, but they were the best swordsmen and archers he and Kachiun could field. At a word from either of them, they would attack.

Khasar looked at Kachiun once again, controlling his anger at the dumb insolence of the warriors facing them. His hand dropped to his sword hilt in unmistakable signal. Kachiun held his gaze for a moment and the warriors on both sides tensed for bloodshed. Almost imperceptibly, Kachiun moved his head a finger's width left and right. Khasar frowned, showing his teeth in frustration for an instant. He leaned in to the closest of those before the gate, breathing into his face.

'I say you are tribeless wanderers, without marks of rank or blood,' Khasar said. 'Don't leave your posts while I am gone. I am going to ride into the city over your bodies.'

The man was sweating and he blinked at the growling voice too close to his neck.

Khasar remounted and he and Kachiun swung away from the pools of light and the promise of death. As soon as they were clear, Kachiun edged his mare over and tapped a hand to his brother's shoulder.

'It has to be the Broken Lance. Ogedai is in the city and someone does not want us riding to his aid tonight.'

Khasar nodded, his heart still hammering. It had been years since he had seen such a show of rebellion from warriors of his people. He was raging, his face flushed.

'My ten thousand will answer the insult,' he snapped. 'Where is Tsubodai?'

'I have not seen him since he went to Ogedai today,' Kachiun replied.

'You are senior. Send runners to his tuman and to Jebe. With them or without them, I am going into that city, Kachiun.'

The brothers and their bondsmen split up, riding different paths that would bring forty thousand men back to the gates of Karakorum. For a time, the noises on the other side of the door died almost to nothing. With silent gestures, Tsubodai and Tolui lifted a heavy couch, grunting with the effort. It took both of them to shove it across the entrance.

'Are there any other ways in?' Tsubodai murmured.

Ogedai shook his head, then hesitated.

'There are windows in my sleeping chamber, but they open onto a sheer wall.'

Tsubodai cursed under his breath. The first rule of battle was to choose the ground. The second was to know the ground. Both had been taken from him. He looked around at the shadowy gathering, judging their mood. Mongke and Kublai were wide-eyed and thrilled to be part of an adventure. Neither realised the danger they were in. Sorhatani returned his gaze steadily. Under that silent stare, he took a long knife from his boot and passed it into her hands.

'A wall won't stop them tonight,' he said to Ogedai, pressing his ear to the door.

They fell silent as he strained to hear, then jumped at a crash that made Tsubodai leap back. A thin trail of plaster dust curled down from the ceiling and Ogedai winced to see it.

'The corridor is narrow outside,' Ogedai muttered, almost to himself. 'They don't have room to run at it.'

'That is good. Are there weapons here?' Tsubodai asked.

Ogedai nodded. He was his father's son. 'I'll show you,' he said, beckoning.

Tsubodai turned to Huran and found the senior man ready at the door. Another crash sounded and voices rose in anger outside.

'Get a lamp lit,' Tsubodai ordered. 'We don't need to stay in the dark.'

Sorhatani set about the task as Tsubodai strode through to the inner rooms. He bowed formally to Ogedai's wife, Torogene. She had lost her sleepy look and smoothed down her hair with water from a shallow bowl, placed there ready for the morning. Tsubodai was pleased that neither she nor Sorhatani seemed to be panicking.

'Through here,' Ogedai said ahead of him.

Tsubodai entered the sleeping chamber and nodded in appreciation. A small lamp still glowed there and he saw the wolf's-head sword of Genghis on the wall above the bed. A bow gleamed on the opposite side, each layer of horn and birch and sinew polished to a rich colour.

'Do you have arrows for it?' Tsubodai asked, bending the hooks open with his thumbs and hefting the weapon. Ogedai smiled at the general's evident pleasure.

'It is not a decoration, general. Of course I have arrows,' he replied. A chest produced a quiver of thirty shafts, each the product of a master fletcher and still bright with oil. He tossed it to Tsubodai.

Outside, the crashing went on. Whoever it was had brought up hammers for the task and even the floor trembled with the blows. Tsubodai crossed to the windows set high in the outer wall. Like the ones in the outer room, they were barred in iron. Tsubodai could not help thinking how he would break in, if he were attacking the rooms. Though they were solid enough, they had not been designed to withstand a determined enemy. That enemy was never meant to get close enough, or to have time to hammer out the bars before Ogedai's Guards cut them to pieces.

'Cover the lamp for a moment,' Tsubodai said. 'I do not want to be visible to an archer outside.' He pulled a wooden chest to the window and crouched on it, then rose suddenly to the barred space, ducking back just as quickly.

'There's no one in sight, lord, but the wall to the courtyard below is barely the height of two men. They will come here, if they can find it.'

'But first they'll try the door,' Ogedai said grimly.

Tsubodai nodded. 'Have your wife wait here, perhaps, ready to call if she hears anything.' Tsubodai was trying to defer to Ogedai's authority, but his impatience showed with every thump from the corridor outside.

'Very well, general.'

Ogedai hesitated, fear and anger mingling, swelling in him. He had not built his city to be torn screaming from life. He had lived with death for so long that it was almost a shock to feel such a powerful desire to live, to avenge. He dared not ask Tsubodai if they could hold the rooms. He could see the answer in the man's eyes.

'It is strange that you are present for the death of another of Genghis' sons, don't you think?' he said.

Tsubodai stiffened. He turned back and Ogedai saw no weakness in his black stare.

'I carry many sins, lord,' Tsubodai said. 'But this is not the time to talk about old ones. If we survive, you may ask whatever you need to know.'

Ogedai began to reply, bitterness welling up in him. A new sound made them both whip round and run. An iron hinge had cracked and the wood of the outer door splintered, a panel yawning open. The lamplight from the room spilled out into the darker corridor, illuminating sweating faces. At the door, Huran speared his blade into them, so that one at least fell back with a cry of pain. The stars had moved part-way across the sky by the time Khasar roused his tuman. He rode at the head in full armour, his sword drawn and held low by his right thigh. In formation behind him were ten groups of a thousand, each with their minghaan officers. Each thousand had its jaguns of a hundred men, led by officers bearing a silver plaque. Even they had their structures: ten groups of ten, with equipment to raise a ger between them and food and tools to survive and fight. Genghis and Tsubodai had created the system, and Khasar hadn't given it a thought when he issued just one order to his quiriltai, his quartermaster. The tuman of ten thousand had formed on the plain, men running to their horses in what looked like chaos before the ranks coalesced and they were ready. Ahead lay Karakorum.