With every able-bodied man working with stones and iron hammers, it still took six days to reduce the canals around Yinchuan to rubble. At first, Genghis looked on the destruction with savage pleasure, hoping the mountain rivers might flood the city.

      It disturbed him to see how the waters rose so quickly on the plain, until his warriors were ankle deep before they had finished destroying the last of the canals. The sultry days brought huge quantities of snow melt down from the mountain peaks and he had not truly considered where all the water might go once it wasn’t channelled down towards the city and the crops.

      Even gently sloping ground became sodden mud by noon of the third day and, though the crops were flooded, the waters continued to rise. Genghis could see the amusement on the faces of his generals as they realised the error. At first, the hunting was excellent as small animals escaping the flood could be seen splashing from far away. Hundreds of hares were shot and brought back to the camp in slick bundles of wet fur, but by then, the gers were in danger of being ruined. Genghis was forced to move the camp miles to the north before water flooded the entire plain.

      By evening, they had reached a point above the broken canal system where the ground was still firm. The city of Yinchuan was a dark spot in the distance and, in between, a new lake had sprung from nothing. It was no more than a foot deep, but it caught the setting sun and shone gold for miles.

      Genghis was sitting on the steps leading up to his ger when his brother Khasar came by, his face carefully neutral. No one else had dared to say anything to the man who led them, but there were many strained faces in the camp that evening. The tribes loved a joke and flooding themselves off the plain appealed to their humour.

      Khasar followed his brother’s irritated gaze out onto the expanse of water.

      ‘Well, that taught us a valuable lesson,’ Khasar murmured. ‘Shall I have the guards watch for enemy swimmers, creeping up on us?’

      Genghis looked sourly at his brother. They could both see children of the tribes frolicking at the water’s edge, black with stinking mud as they threw each other in. Jochi and Chagatai were in the centre of them as usual, delighted with the new feature of the Xi Xia plain.

      ‘The water will sink into the ground,’ Genghis replied, frowning.

      Khasar shrugged.

      ‘If we divert the waters, yes. I think it will be too soft for riders for some time after that. It occurs to me that breaking the canals may not have been the best plan we have come up with.’

      Genghis turned to see his brother watching him with a wry expression and barked a laugh as he rose to his feet.

      ‘We learn, brother. So much of this is new to us. Next time, we don’t break the canals. Are you satisfied?’

      ‘I am,’ Khasar replied cheerfully. ‘I was beginning to think my brother could not make an error. It has been an enjoyable day for me.’

      ‘I am pleased for you,’ Genghis said. Both of them watched as the boys on the water’s edge began to fight again. Chagatai threw himself at his brother and they thrashed together in the muddy shallows, first one on top, then the other.

      ‘We cannot be attacked from the desert and no army can reach us here with that new lake in the way. Let us feast tonight and celebrate our victory,’ Genghis said.

      Khasar nodded, grinning.

      ‘Now that, my brother, is a fine idea.’

      Rai Chiang gripped the arms of his gilded chair, staring out over the drowned plain. The city had warehouses of salted meat and grain, but with the crops rotting, there would be no more. He turned the problem over and over in his mind, despairingly. Though they did not yet know it, many in the city would starve to death. His remaining guards would be overwhelmed by the hungry mob when winter came and Yinchuan would be ruined from within.

      As far as his eye could see, the waters stretched back to the mountains. Behind the city to the south, there were still fields and towns where neither the invaders nor the flood had yet reached, but they were not enough to feed the people of the Xi Xia. He thought of the militia in those places. If he stripped every last man from those towns, he could assemble another army, but he would lose the provinces to banditry as soon as the famine began to bite. It was infuriating, but he could not see a solution to his troubles.

      He sighed to himself, causing his first minister to look up.

      ‘My father told me always to keep the peasants fed,’ Rai Chiang said aloud. ‘I did not understand its importance at the time. What does it matter if a few starve each winter? Does it not show the displeasure of the gods?’

      The first minister nodded solemnly.

      ‘Without the example of suffering, Majesty, our people will not work. While they can see the results of laziness, they toil in the sun to feed themselves and their families. It is the way the gods have ordered the world and we cannot stand against their will.’

      ‘But now, they will all go hungry,’ Rai Chiang snapped, tired of the man’s droning voice. ‘Instead of a just example, a moral lesson, half our people will be clamouring for food and fighting in the streets.’

      ‘Perhaps, Majesty,’ the minister replied, unconcerned. ‘Many will die, but the kingdom will remain. The crops will grow again and, next year, there will be an abundance for the mouths of the peasants.