But, on a thick stormy night (July 4th), six bridges of boats were quickly swung across the stream lower down, that is, on the east side of Lobau, while a furious cannonade on the north side misled their foes.

The crossing was effected without loss by Oudinot and Massena; and sunrise saw the whole French army advancing rapidly northwards, thereby outflanking the Austrian earthworks, which were now evacuated.
Charles was outmanoeuvred and outnumbered.

His brother, the Archduke John, was at Pressburg with 20,000 men, watched hitherto by Davoust.
But the French Marshal cleverly withdrew his corps, leaving only enough men to impose on that unenterprising leader.

Other Austrian detachments were also far away at the critical time, and thus Napoleon had a superiority of force of about 50,000 men.

Nevertheless, the defence at Wagram was most obstinate (July 6th).