All the while Napoleon carefully scrutinised the regular intelligence reports sent to him by Davout. As soon as the threat to Vienna became clear Archduke Charles had turned his army round and set off along the north bank of the Danube in a bid to reach his capital city before the French. There was little chance of that, Napoleon calculated, since the Austrian army had always marched at a ponderous pace. The only news that concerned him came from Italy, where Archduke Charles’s brother, Archduke John, had bested the French army there. It was possible that John might march back towards Vienna in an attempt to combine the Austrian armies against Napoleon.

Early in May, the spires and roofs of the Austrian capital came within sight of the French army and Napoleon gave the order for the artillery to prepare to bombard Vienna. Before the guns could open fire the gates of the city opened and a small party of civilians rode out.

‘I wonder what they want?’ Berthier mused as he raised his telescope and watched them cautiously approach the French pickets. He turned to his Emperor. ‘Maybe they want to sue for peace already.’

‘I would hope so,’ Napoleon replied. ‘But if they intend to defend Vienna, then this time I will not hesitate to flatten the city. There will be no third chance for Emperor Francis to defy me.’ Napoleon gestured for the telescope and squinted through the eyepiece. There were five men in civilian clothes, together with a small mounted escort from the city’s militia.

‘Have them brought to the main battery,’ Napoleon instructed Berthier.‘I’ll meet them there. Might as well let them see what they can expect if they fail to meet my demands.’

‘Yes, sire.’ Berthier nodded and wheeled his horse away to carry out the order. Napoleon turned his gaze from the approaching horsemen to the defences of the city beyond. There were a handful of forts guarding the approaches to Vienna, and then the walls. However, there were no signs of life in any of the forts, and no flags or regimental standards flying over them. He lowered the telescope with a slight frown and muttered, ‘What the hell are they playing at?’

Half an hour later Napoleon, together with Berthier and a squadron of Guard cavalry, rode into the main battery to meet the enemy deputation. On either side the line of twelve-pounders stretched out across the Austrian countryside. Fifty yards behind them lay the caissons, loaded with powder and shot, ready to feed the guns when they opened fire on Vienna. The gun crews had completed their preparations and stood close by their weapons, watching the Austrians curiously. At Napoleon’s approach the gunners cheered and he indulged it a moment as he slowed his mount to a slow walk and fixed the Austrians with a hard stare. They removed their hats and bowed their heads curtly as the French Emperor raised a hand to quieten his men. Once the cheers had died away Napoleon cleared his throat and addressed the man at the head of the Austrian deputation. The official was tall and thin, and his dark curls were streaked with grey. His coat was finely embroidered with gold lace and a broad red ribbon hung across his shoulder. Napoleon spoke curtly.

‘What is the purpose of your presence here?’

‘Sire, I represent the mayor of Vienna. His honour respectfully requests an audience with you.’

‘Your name?’

‘Baron Karinsky, sire.’

‘Tell me what your master wants.’

‘Yes, sire. He wishes to discuss terms for the surrender of Vienna.’

‘Vienna? I see.’ Napoleon paused. ‘And has Emperor Francis agreed to the surrender of his capital?’

‘As far as I understand, sire.’

‘What does that mean?’

‘His imperial majesty and the court have left the city, sire. The mayor was left in charge with orders to defend it for as long as is practicable.’

‘Then this offer relates to Vienna alone?’ asked Berthier.

‘Indeed, sir.’

‘There is no intention on the part of Emperor Francis to discuss an armistice?’

‘Not as far as I am aware.’

Berthier exchanged a look with Napoleon, who let out a brief sigh of frustration before he continued addressing Karinsky.

‘So why is the mayor preparing to discuss surrender before we have fired a single shot?’

The Austrian gestured towards the city. ‘The garrison has already withdrawn from the walls, sire. On the orders of Archduke Charles. All that remains is the militia. Accordingly, the mayor has determined that he cannot defend the city. Out of compassion for the inhabitants of Vienna he believes it would be better to surrender rather than waste lives in a pointless attempt to resist you, sire.’

‘Where is the garrison now?’ Napoleon snapped.

‘They have retreated across the Danube.’

Napoleon stared at the man briefly. ‘And the bridges are intact?’

The man lowered his eyes as he replied. ‘They were when I left the city, sire.’

Napoleon turned to Berthier. ‘Send a cavalry division forward. Tell Bessiиres I want his men to take those bridges at once. We must have access to the far bank if we are to—’

He was interrupted by a faint roar and looked towards Vienna. Beyond the city skyline he could see a billowing column of smoke rising up into the clear sky. A moment later there was a second explosion and more smoke, followed by two more blasts that echoed across the landscape towards the startled leading elements of the French army.

‘They’ve blown the bridges,’ Berthier said quietly.

Napoleon nodded, and glared at Baron Karinsky. ‘Tell the mayor Vienna is to surrender unconditionally. If he does not surrender the city within the hour, then I will order my guns to pulverise your capital. Is that clear?’

Karinsky shook his head. ‘Sire, I am not authorised to negotiate with you. My master simply sent me here to invite you to speak with him.’

‘There is nothing to say. There will be no negotiations. Tell him that I demand he surrender, and that if he fails to do so then the death and destruction that I will rain down on Vienna will be his responsibility.’

The Austrian opened his mouth to protest but Napoleon took out his watch and glanced down briefly. ‘It is now just gone eleven o’clock. If the city has not surrendered by noon I will order the guns to open fire. It would be wise of you to waste no time in informing the mayor of my terms.’

Karinsky frowned and then abruptly turned his horse about and spurred it into a gallop as he headed back down the road to Vienna.

As soon as the gates of Vienna were thrown open to the French army, Napoleon and his chief engineer, General Bertrand, rode through the city to assess the condition of the demolished bridges. The Austrian engineers had done a thorough job. The central spans of each bridge had been blown, and the buttressed piles were little more than heaps of masonry in the swiftly flowing current of the Danube. On the far side of the river the enemy was busy building barricades across the ends of the ruined bridges. On the flanks artillery batteries were being constructed to cover the river in case the French engineers attempted to make any repairs to the blown spans.

Napoleon gazed at the bridges with a heavy heart. The enemy would be safe until the French could find another way across the river.

General Bertrand had finished surveying the bridges and the Austrian forces beyond, and clicked his tongue. ‘It would be suicide to attempt any repairs, sire.’

‘I can see that for myself,’ Napoleon replied testily. ‘If we can’t cross here, then we must find somewhere else.’

‘Yes, sire.’ Bertand nodded thoughtfully as he removed his hat and scratched the thin strands of hair plastered to his skull. ‘The main problem is the current. As you can see, the river flows quickly, particularly at this time of year. Any sudden storms can only make matters worse. If there is a sudden flood, then our pontoons could be carried away.’