The storm broke just after night fell over the Danube. Lightning illuminated the landscape in brilliant flashes of dazzling white which caught thousands of men, horses, guns and silvery streaks of rain in a frozen tableau for an instant before plunging the world back into darkness. Then, as the men marched forward through the mud towards the pontoon bridges, the thunder crackled and boomed like a vast cannonade in the heavens.

‘It could hardly be better,’ Napoleon commented to Berthier as they sat on their horses, watching the first columns of Masséna’s corps move forward to the river bank, ready to cross over the moment the bridges were swung into place. Napoleon gestured towards the western side of the island, nearly two miles away. ‘This storm, and the diversionary attack from Mühlau, will provide perfect cover for Masséna’s assault.’

Berthier nodded, and reached for his pocket watch. He waited a moment, and then read the time as lightning flashed overhead.

‘Just gone nine o’clock, sire. Less than ten minutes to go now.’

They waited in the darkness while the rain hissed down, pattering off the flat tops of the soldiers’ shakos and soaking through their greatcoats and the uniform jackets beneath. Around them, the trees that lined the river bank swayed in the gusts of wind that sounded like the sea as it swept through the leafy boughs. Every time the lightning burst across the landscape the soldiers looked like statues, Napoleon mused as he hunched his neck down into his collar to try to keep the water from trickling down his neck. Then, at the appointed time, there was a deep roar from the west that echoed across the island as the guns massed opposite Mühlau blasted the Austrian lines. At the same time General Legrand would be launching his diversionary attack, engaging the enemy outposts as aggressively as he could to draw Archduke Charles’s attention away from his left flank.

As soon as the cannonade began, the five hundred grenadiers of Masséna’s assault force rushed the small boats they had been issued down the bank and into the river, before clambering aboard and paddling across the current as swiftly as possible. No shots were fired from the Austrian sentries, who were either sheltering from the storm or distracted by the furious sounds of battle away to the west. In the darkness, Napoleon could just make out the boats surging across the river, the men landing and then heading cautiously up the far bank, muskets at the ready.