Not so Tsubodai. None of the Guards dared to come close to that man as he stood and silently dared Chagatai to protest. Though Tsubodai remained still, it was the stillness of a snake, or a sapling bent and ready to spring back.

Finally, Chagatai faced the Guard officer with one eyebrow raised. He endured being patted down, but he had no hidden weapons and the door swung open. He walked in alone. As it closed behind him, he heard Khasar begin to argue as he was held back. Chagatai was pleased Tsubodai and his uncles would not be witnesses. He had gambled and lost, but there was no shame in it, no humiliation. Ogedai had gathered loyal men to him, just as Chagatai had. His brother's generals had proved more resourceful than his own. As it had been the night before, one brother would still be khan, and the other? Chagatai grinned suddenly as he saw Ogedai at the far end of the hall, sitting on a throne of white stone inlaid with patterns of gold. It was an impressive sight, as it was intended to be.

As he walked closer, Chagatai saw Ogedai's hair was damp, loose and black on his shoulders. A purple mark on his cheek was the only visible proof of the night before. Despite the grandeur of the throne, his brother wore a simple grey deel over leggings and a tunic, with no more decoration than any herder of the plains.

'I am glad to see you well, brother,' Chagatai said.

Ogedai tensed as Chagatai walked smoothly towards him, his steps echoing.

'Let us not play games,' he replied. 'I have survived your attacks. I will be khan at sunset today.'

Chagatai nodded, still smiling. 'No games then, but you know, the strange thing is I spoke the truth. Part of me was dreading finding you killed. Ridiculous, yes?' He chuckled, amused at the complexity of his own emotions. Family was a peculiar thing. 'Still, I did what I thought best. I have no regrets or apologies. I think father would have enjoyed the risks I took.' He bowed his head. 'You'll forgive me if I don't congratulate you on your triumph.'

Ogedai relaxed subtly. He had spent years thinking of Chagatai as an arrogant idiot. He had almost missed him growing into a man used to responsibility and power. As Chagatai came to stand before him, Ogedai's Guards stepped out and commanded him to kneel. He ignored them, remaining on his feet and looking around the room with an interested expression. It was a huge space to a warrior more used to the gers of the plains. The morning light flooded in from a window overlooking the city.

One of the Guards turned to Ogedai for permission and Chagatai smiled slightly. With any other prisoner, the man would have struck him down, or even hamstrung him to make him kneel. The hesitation acknowledged Chagatai's power even as they sought to humble him.

Ogedai could almost admire his brother's careless courage. No, he could admire it, even after such a night. The shadow of Genghis hung over them both and perhaps it always would. Neither they nor Tolui could ever match their father's achievement. By any standard, they were lesser souls and had been from the moment they were born. Yet they had to live and grow and become men, skilful in their crafts. They had to thrive in that shadow – or let it smother them.

No one else understood Ogedai's life as Chagatai did, not even their brother Tolui. He wondered again if he was making the right decision, but in that too he had to be strong. A man could waste his life worrying, that was all too clear. Sometimes you simply had to choose and shrug, however it came out, knowing that you could not have done more with the bones you were given.

Ogedai faced his brother and wished one last time that he could know how long he had to live. Everything depended on it. His son did not have the ruthless will to inherit. If Ogedai died that very day, Guyuk would not follow in the line of their father, the line of Genghis. It would pass to the man standing before him. Ogedai searched for calm, though his heart thumped and pattered in his chest, spreading a constant ache until it became like a blade between his ribs. He had not slept and he knew he ran the risk of collapse in dealing with Chagatai that morning. He had drunk a jug of red wine to steady his nerves and used a pinch of the foxglove powder. He could still taste the bitterness on his tongue and his head ached as if it was being slowly crushed.

For all he knew, he might rule as khan for just days before his heart gave out and burst in his chest. If that was his fate and he had killed Chagatai, the nation would tear itself apart in civil war. Tolui was not strong enough to hold them together. Neither he nor Ogedai's son had gathered loyal generals to protect them through such an upheaval. Power would triumph over blood in that struggle.

The man who stood before him, his tension hidden, was perhaps the best hope for the nation. More, Chagatai was the one Genghis would have chosen if their brother Jochi had never been born. Ogedai felt his damp hair itch and he rubbed it unconsciously. The Guards still looked to him, but he would not let them beat Chagatai to his knees, not that day, though part of him yearned to see it.

'You are safe here, brother,' he said. 'I have given my word.'

'And your word is iron,' Chagatai murmured, almost automatically.

Both of them recalled their father's beliefs and honoured them. The great khan's shadow clung to them like a cloak. The shared memories made Chagatai look up and frown, suddenly at a loss. He had expected to be killed, but Ogedai seemed troubled rather than triumphant or even vengeful. He watched with interest as Ogedai turned to his Guard officer.

'Clear the room. What I have to say is for my brother alone.' The man began to move but Ogedai stopped him with a raised hand. 'No, bring Orlok Tsubodai as well.'

'Your will, my lord,' the officer replied, bowing deeply.

In just moments, the Guards along the walls were marching to the great copper doors. Tsubodai came in at their call. Outside, Khasar could be heard still arguing with the officers before the door swung shut, leaving the three men alone in the echoing space.

Ogedai rose from the throne and stepped down so that he was at Chagatai's level. He crossed to a small table and poured himself a cup of airag from a jug, drinking deeply and wincing as it stung ulcers in his mouth.

Chagatai glanced at Tsubodai only to find the man glaring at him like an enemy. He winked at the general and looked away.

Ogedai took a slow breath and his voice shook at the strain of saying what he had kept hidden for so long.

'I am my father's heir, Chagatai. Not you, or Tolui, or Kachiun, or Jochi's son, or any of the generals. As the sun sets today, I will accept the oath of the nation.' He paused and neither Chagatai nor Tsubodai interrupted as the silence stretched. Ogedai looked out of the tall window, enjoying the sight of his city, though it was quiet and frightened after such a night.

'There is a world outside the one we know,' he said softly, 'with cultures and races and armies who have never heard of us. Yes, and cities greater than Yenking and Karakorum. To survive, to grow, we must remain strong. We must conquer new lands, so that our army is always fed, always moving. To stop is to die, Chagatai.'

'I know this,' Chagatai said. 'I am not a fool.'

Ogedai smiled wearily. 'No. If you were a fool, I would have had you killed in the courtyard with your bondsmen.'

'Then why am I still alive?' Chagatai said. He tried to keep his tone casual, but this was the question that had burnt him ever since he saw Tsubodai in the courtyard of the palace.

'Because I may not live to see the nation grow, Chagatai,' Ogedai said at last. 'Because my heart is weak and I could die at any moment.'

The two men facing him stared as if struck. Ogedai couldn't bear to wait for their questions. Almost with relief, he went on, the words spilling out.