Napoleon stared at the door for a moment. Then he picked up his dividers and walked across to the map. He adjusted the instrument to fit the scale and measured off the distance that Ney’s corps had been ordered to march. The dividers passed over territory marked as mountainous and broken by many streams and tributaries. For long stretches there were no roads marked on the map. It was, as Ney had said, roughly a hundred and twenty miles. A fresh division of infantry might have encompassed it, Napoleon told himself, but a whole army corps, burdened by its wagons and artillery, could never hope to march such a distance in three days.

Why had he not seen this? It was a lapse of judgement. He would not have made such an error ten years ago, or even five.Was age making his mind less acute? He dismissed the thought. He was not yet forty, surely not old enough for that. But what if his judgement was at fault? What if the organisational brilliance that had made him the master of Europe had become corrupted by his success? It would not be the first time that a great man had fallen prey to the temptation to view every decision he made as infallible.The prospect appalled him. For a moment Napoleon was furious with himself for not making the correct allowances for Ney’s movement.Then he forced the very idea of it from his mind. It could not be his fault.

In fact, he recalled that he had given the order without consulting the map. It had been a hectic night when he had dictated his plans to Berthier. Why had Berthier not mentioned the difficulties that Ney would face in keeping to the allotted time for his advance? It was Berthier who had failed him, not Ney. He decided that he must pay closer attention to Berthier from now on. Perhaps the man was growing too old, too weary, to carry the burden of being the Emperor’s chief of staff. Berthier would have to be watched to ensure that he did not make any more such mistakes, Napoleon told himself sadly. Berthier was a good man, but he had let his Emperor down and caused him to blame wrongly a fine officer like Ney. Well, Napoleon comforted himself, his subordinates were only human. Once the campaign was over he would have a word with Berthier and suggest that the chief of staff apologise to Ney for making him the target of Napoleon’s anger.

There was a knock at the door, and Berthier entered. Napoleon stared at him for a moment, uncertain whether to be angry with the man for causing the earlier scene, or to feel pity for Berthier’s mortal failings. In the end he opted for the latter, and smiled condescendingly.

‘What is it?’