‘No reports of any serious opposition, sire. The Austrians seem to be retreating right across our front.’ Berthier sifted through a few more sheets of paper before he looked up again. ‘Casualties are minimal.’

‘Good. And what of the bridges? Are they still in one piece?’

‘As far as I know, sir. At least, there have been no reports to the contrary.’

Napoleon stared at his subordinate for a moment, wondering if he could trust his junior officers to keep him fully informed of the army’s progress across the river. After the debacle of the last attempt to force a crossing of the Danube, Napoleon was determined to ensure that the army’s lines of communication were unhindered. He pushed the bowl to one side. ‘Berthier, send an officer to the river bank. I want to know the instant anything happens that might frustrate our plans, in any way. Is that clear?’

‘Yes, sire.’

Napoleon gazed at the map, deep in concentration. By dawn three army corps and the Imperial Guard would be drawn up in a line facing north across a six-mile front from the bank of the Danube across the plain to the east. A hundred thousand men. Opposed to them would be a hundred and fifty thousand Austrians. Napoleon was confident that his men could hold their line, even though outnumbered, until the last formations of the Grand Army crossed the Danube and swelled the total to over a hundred and eighty thousand men. If Archduke Charles retreated, then the Grand Army would be obliged to pursue him, all the time stretching their lines of communication, and being forced to leave behind men tasked with guarding vital supply routes.

Very well, then, Napoleon resolved, the enemy must not be given any chance to break contact. At first light, the first three corps must be launched against the Austrians, forcing them to stand and fight.

When the sun rose across the plain in the morning, it was clear that the Austrians had been caught by surprise. Through his looking glass Napoleon could see enemy lines scattered across the landscape. The largest concentration of Austrian forces was between the villages of Aspern and Essling where the diversionary attack had struck the previous evening. Elsewhere individual units were hurriedly forming up into lines to face the coming onslaught. As the light strengthened across the drenched fields, he saw that some of the enemy formations were already pulling back, heading for the Russbach river. The bank was raised on the far side of the river and would provide the Austrians with some defence against a French attack.

During the first hours of the morning there was no attempt to counter-attack and most of the French soldiers had the chance to chew on some bread and sip some water. They stood in the muddy fields, muskets slung over their shoulders as thin wisps of steam rose from their uniforms into the warm air. As they waited a steady stream of infantry, cavalry and artillery hurried across the river. Three more corps were due to cross the Danube during the day, and the last, commanded by Marmont, would join them on the morrow. In little over a day, almost all the army would have reached the far bank. It was an achievement to be proud of, Napoleon mused to himself as he stretched his shoulders and watched the men of Prince Eugиne’s corps stepping out across the pontoon bridges.

His heart warmed at the thought of his stepson. Eugиne had proved himself to be an able commander and, more important, a loyal subordinate - unlike the commander of the corps that was waiting to cross after Eugиne’s men. Marshal Bernadotte had become increasingly arrogant in the years since Napoleon had been crowned Emperor. Recently, there had been reports from some of his officers that Bernadotte had been speaking very openly of his superiority to the Emperor in military affairs. While it was tempting to dismiss the marshal and be done with him, the fact was that Bernadotte was popular with his men, and well connected amongst the politicians in Paris. He would present more of a danger if left to his own devices in the capital than here in the field, where Napoleon could keep a close eye on him. Even so, there was a limit to how far the Emperor would tolerate such a troublesome officer.

He thrust Bernadotte from his mind and returned to his consideration of Eugиne. It was a shame that he had not fathered such a fine man, Napoleon reflected sadly. That had been a fond hope and ambition of his marriage to Josephine. But there was no chance of her bearing another child now. She was too old for that, and even if she had still been fertile she would not be prepared to risk another childbirth. Yet France needed an heir to the imperial throne. Without a son to succeed him, Napoleon could not give his empire the stability it so desperately needed. Since he had fathered a son by the Polish Countess Walewska, he knew that his own fertility was not at fault. If there was to be an heir, then he must find himself a new wife. Yet he shrank from the consequences of that knowledge. Despite the discovery of Josephine’s numerous affairs, and her failure to give him a son, Napoleon loved her more deeply and surely than any woman he had ever known.

He sighed heavily. Once the campaign was over, and Austria had been humbled, then he would have to deal with the matter of providing his empire with a successor, no matter how much pain that would cause him, and Josephine. Duty and destiny must prevail over emotion, he resolved.

He was disturbed by the arrival of a young dragoon officer who stood to attention and saluted as he stood before his Emperor.

‘What is it?’ Napoleon snapped.

‘Sire, Marshal Massйna sends his compliments and begs to inform you that the Austrians are beginning to withdraw from Essling.’

‘Are they now?’ Napoleon frowned. It seemed that Archduke Charles had finally realised the danger of his situation and was starting to extricate his army. ‘Tell Massйna that he is to press forward at once. He is to push the enemy back, and stay in contact with them. They must not be allowed to escape, or be given any respite. Massйna must drive all before him. Now go!’

‘Yes, sire!’

Throughout the afternoon the French soldiers pressed forward, driving the enemy back across the plain. The last clouds had long since gone and the sun blazed down from a clear blue sky. But while there was serenity in the heavens, the Marchfeld was marked by great banks of rolling gunpowder smoke and the litter of war. Bodies of the dead and wounded lay strewn in the trampled grass, together with discarded equipment, shattered gun carriages and lame or abandoned horses that grazed between the corpses. The air was heavy from the heat, and reverberated with the sounds of cannon and the lighter crackle of musket fire.

Late in the afternoon Napoleon and his escort rode forward to assess the situation. He stopped by a small church on a dusty road heading north from Aspern, and climbed its tower with Berthier. There was little space at the top, and they had to squeeze past the old bronze bell before they could open the shutters and look out over the battlefield. Both men raised their telescopes and slowly swept them along the French line, taking in the formations of men and horses advancing under their tricolour and imperial eagle banners. They were dark against the shimmering gold of wheat fields, and the verdant green of meadows.

Napoleon could see that his army formed a giant wedge, driven into the centre of the Austrian line. He felt the familiar excitement tingle in his scalp as he viewed the over-extended enemy.

‘Berthier, do you see?’

‘Sire?’ Berthier lowered his looking glass and waited patiently while his Emperor briefly examined the battlefield once again before he lowered his own glass and turned round with a cold smile.

‘Berthier, we have them, provided we strike swiftly. Come!’