Khasar's outriders reported other tumans on the move all around him. No one in the nation slept now. To the smallest child, they knew this was the night of crisis, so long feared.

Khasar had his naccara drummers sound a rhythm: dozens of unarmed boys on camels whose sole task was to inspire fear in an enemy with a rolling thunder. He heard it answered ahead and on the left, as other tumans took up a warning and a challenge. Khasar swallowed drily, looking for Kachiun's men ahead. He had the feeling that events were slipping from his control, but he could do nothing else. His path had been set when men at the gate had dared to refuse a general of the nation. He knew they were Chagatai's, but the arrogant prince had sent them out without his unit markings, to do his work like assassins in the night. Khasar could not ignore such a threat to his authority – to all the stages of authority that he represented, down to the youngest drummer on a sway-backed beast. He dared not think of his nephew Ogedai trapped in his own city. He could only react and force his way in, hoping there would be someone still alive to save.

Kachiun joined him, with Jebe's Bearskin tuman and Tsubodai's ten thousand. Khasar breathed in relief as he saw the banners stretching away into the dark, a sea of horses and flags. Tsubodai's warriors knew their general was in the city. They had not disputed Kachiun's right to order them in his place.

Like a mountain slowly falling, the vast array of four tumans drew close to the western gate of Karakorum. Khasar and Kachiun rode forward, hiding their impatience. There was no need for bloodshed, even then.

The men at the gate remained still, their weapons sheathed. Whatever their orders had been, they knew that to draw a blade was to invite instant destruction. No man wanted to be first.

The tableau held, with just the snorting of horses and fluttering banners. Then out of the darkness rode a new group of men, their passage lit with burning torches held by bannermen, so that in an instant, every man there knew that Chagatai had arrived.

Kachiun could have ordered Khasar to block Genghis' son and had his own tumans cut a way into the city. He felt the weight of the decision hang on him, time running slowly as his pulse raced. He was not a man to hesitate, but he was not at war. This was not the desert of Khwarezm or the walls of a Chin city. He let the moment pass, and as it went, he clutched at it desperately, almost throwing away his life when it was too late.

Chagatai rode in like a khan, his bondsmen surrounding him in square formation. Some of the men at the gate went sprawling as horses knocked them down, but he did not look round. His gaze was fixed firmly on the two older generals, his father's brothers, and the only men who mattered in the camp that night. He and his horse were armoured and the air was cold enough for Kachiun to see plumes of mist from man and beast alike. Chagatai wore an iron helmet, with a horse'smane crest whipping through the air as he came in. He was no longer the boy they had known and both men tensed under his flat stare.

Khasar made a hissing sound under his breath, signalling his anger to his brother. They knew Chagatai was there to prevent them entering Karakorum. They were not yet sure how far he would go to keep them outside.

'It is late to be training your men, Chagatai,' Khasar snapped, his voice loud.

They were separated by less than fifty paces, closer than he had been allowed to the man in a month. Khasar ached to reach for his bow, though the armour would likely save his target and then there would be a blood-letting on a scale unseen since they had destroyed the Xi Xia. The prince shrugged as he sat his horse, smiling with cold confidence.

'I am not training, uncle. I am riding to see who threatens the peace of the camp in darkness. I find it is my own uncles, moving armies in the night. What am I to make of it, eh?' He laughed and the men around him showed their teeth, though their hands never left the bows, swords and lances with which they fairly bristled.

'Be careful, Chagatai,' Khasar said.

The prince's expression went hard at the words. 'No, uncle. I will not be careful when armies ride through my land. Return to your ger, your wives and children. Tell your men to go back to theirs. You have no business here tonight.'

Khasar took a breath to roar an order and Kachiun shouted before he unleashed the tumans.

'You have no authority over us, Chagatai! Your men are outnumbered, but there is no need for blood to be spilled. We will enter the city tonight, now! Stand aside and there will be no strife between us.'

Chagatai's horse sensed his surging emotions and he had to turn it on the spot to stay in position, sawing its mouth with the reins. They could read the triumph on his face and, privately, both men despaired for Ogedai in the city.

'You misjudge me, uncle,' Chagatai shouted, making sure he was heard by as many ears as possible. 'You are the ones trying to force your way into Karakorum! For all I know, you are planning bloody murder in the city, a coup, with my brother's head as the prize. I have come to stop you entering, to keep the peace.' He sneered at their surprise, his face savage as he waited for the arrows to fly.

Kachiun heard movement on his right and jerked in the saddle to see vast ranks of men moving into position around him, their officers lit with torches. He could not judge the numbers in the starlight, but his heart sank as he saw the banners of those loyal to Chagatai. The two sides glowered at each other, roughly equal, but Chagatai had done enough and he knew it. Kachiun and Khasar could not begin a civil war in the shadow of Karakorum. Kachiun looked east for the first signs of dawn, but the sky was dark and Ogedai was on his own.

'Down, Huran!' Tsubodai snapped.

He notched an arrow on the string as he ran. Huran dropped flat below the hole in the door and Tsubodai sent a shaft hissing through into the darkness beyond. He was rewarded by a choking cry as he drew and loosed again. The distance was no more than ten paces. Any warrior of the tribes could have hit the gap, even under pressure. As soon as Tsubodai shot the second arrow, he dropped to one knee and rolled out of the way. Before he had stopped moving, a shaft buzzed into the room, going almost too fast to see. It struck behind Tsubodai with a loud thump, quivering in the wooden floor.

Huran had taken up a position with his back flat to the door, his head turned towards the hole. He was rewarded as a hand darted through, fingers scrabbling for the locking bar below. Huran swung his sword horizontally, cutting through meat and bone and almost jamming the blade into the wood. The hand and part of the forearm dropped to the ground and an unearthly screaming sounded before it too was choked off. Perhaps those outside had led the man away to be tended, or killed him themselves.

Tsubodai nodded to Huran as their eyes met. Regardless of rank, they were the two most capable warriors in the room, able to remain calm and think, even when the smell of blood was thick.

Tsubodai turned to Ogedai. 'We need a second position, lord.'

The man who would be khan was standing with his father's wolf's-head sword drawn, breathing too shallowly and looking paler than Tsubodai had seen him before. Tsubodai frowned to himself as Ogedai didn't respond. He spoke louder, using his voice to snap the younger man out of his trance.

'If the door goes, they will rush us, Ogedai. You understand? We need a second place, a line of retreat. Huran and I will stay by this door, but you must get the boys and women back to the inner rooms and block the door as best you can.'

Ogedai turned his head slowly, dragging his eyes away from the dark hole that seemed to vomit forth the hatred of those behind it.