The defences of the Bohemian town of Ratisbon looked formidable indeed, Napoleon silently conceded as he swept his telescope along the aged walls and ditches confronting him. The retreating Austrian army had hastily thrown up more earthworks to bolster the existing defences and cannon muzzles were discernible in the embrasures of each redoubt, with more cannon mounted on the thick, squat towers of the old town. Here and there, the white-uniformed figures of the enemy regarded the French host approaching the town. Beyond the walls the pitched roofs and church spires were vague in the last vestiges of the early morning mist that had risen up from the Danube. On the far side of the river Napoleon could just pick out the faint trails of smoke rising up from the Austrian camp on the far bank.

He frowned as he lowered the telescope and snapped it shut. Archduke Charles and his men had escaped the trap Napoleon had set for them. Ratisbon had been in French hands until a few days before, and the enemy had been caught with their backs to the river. But the commander of the garrison had surrendered after a brief resistance, leaving the bridge across the Danube intact. So the Austrians had crossed to the north bank and left a strong force behind to defy their pursuers. Archduke Charles had surprised him, Napoleon reflected. He had fully expected the Austrians to fall back towards Vienna to protect their supply lines and defend their capital. Instead, the enemy general had crossed the river into Bohemia, leaving the road to Vienna open. Only it was not as simple as that, Napoleon realised well enough. If he led his army towards Vienna, he would be inviting the Austrians to fall on his supply lines in turn. That might be an unavoidable risk.

Napoleon turned round to face his staff officers. ‘Gentlemen, Ratisbon must be taken if we are to cross the Danube and force the enemy to face us on the battlefield.’

General Berthier, Napoleon’s chief of staff, briefly raised his eyebrows as he glanced past his Emperor towards the defences of the town, barely a mile away. He swallowed as his gaze switched back to Napoleon.

‘Very well, sire. Shall I give the order for the army to prepare for a siege?’

Napoleon shook his head.‘There is no time for a siege. The moment we settle down to dig trenches and construct batteries the Austrians have the initiative. Moreover, you can be sure that our other enemies . . .’ Napoleon paused and smiled bitterly, ‘and even some of those who call us friends will take great comfort from the delay. It would not take much prompting for them to side with Austria.’