Inspired by the rebellious Spaniards’ success against Napoleon, Austria launched a campaign to liberate neighboring countries from Napoleon’s rule. Hoping to inspire large-scale revolution throughout the Confederacy of the Rhine, Austrian troops invade Bavaria on April 8, 1809, proclaiming a War of German Liberation. But the people of Bavaria, who had profited from Napoleon’s earlier defeat of Austria, rallied once again around Napoleon as he assembled his troops for battle.
“Austria wants to get slapped; she shall have it,” Napoleon boasted. “If the Emperor Francis attempts any hostile move, he will soon have ceased to reign.”
Two weeks later, Napoleon battered the Austrians, forcing them to retreat back across the border. He then swooped down on Vienna once again, capturing the city on May 13. Even with the capital in enemy control, Emperor Francis I refused to sign a peace treaty. Napoleon would have to crush the massive Austrian army to bring him to the negotiations table.
From marshy Lobau Island west of Vienna, Napoleon’s army launched an attack against the Austrians on May 22. Despite being outnumbered almost two to one, the French pushed their enemy out of the village of Essling, inflicting heavy losses. However, Austrian troops upstream from the island cut loose a floating flour mill that smashed Napoleon’s pontoon bridges. His troops were cut off from vital reinforcements and supplies. He crossed the river to help reassure them.
More on Wikipedia: http://en.wikipedia.org/wiki/Napoleonic_Wars#War_of_the_Fifth_Coalition_1809