Napoleon lay on the right bank of the Danube; the Austrian army under the Archduke Charles was coming towards the city by the left bank; it was to be a hand-to-hand struggle under the walls of Vienna. The emperor was uncertain of the archduke’s plans, but he was determined that he should not have a chance to reënforce his army. The battle must be fought at once, and he prepared to go across the river to attack him. The place of crossing he chose was south of Vienna, where the large island Lobau divides the stream. Bridges had to be built for the passage, and it was with the greatest difficulty that the work was accomplished, for the river was high and the current swift, and anchors and boats were scarce. Again and again the boats broke apart. Nevertheless, about thirty thousand of the French got over, and took possession of the villages of Aspern and Essling, where they were attacked on May 21st by some eighty thousand Austrians. [Illustration: BATTLE OF WAGRAM. This picture, by Horace Vernet, was first exhibited in the _Salon_ of 1836. It now hangs in the Hall of Battles at Versailles.] The battle which followed lasted all day, and the French sustained themselves heroically. That night reënforcements were gotten over, so that the next day some fifty-five thousand men were on the French side. Napoleon fought with the greatest obstinacy, hoping that another division would soon succeed in getting over, and would enable him to overcome the superior numbers of the Austrians. Already the battle was becoming a hand-to-hand fight, when the terrible news came that the bridge over the Danube had gone down. The Austrians had sent floating down the swollen river great mills, fire-boats, and masses of timber fastened together in such a way as to become battering-rams of frightful power when carried by the rapid stream. All hope of aid was gone, and, as the news spread, the army resigned itself to perish sword in hand. The carnage which followed was horrible. Towards evening one of the bravest of the French marshals, Lannes, was fatally wounded. It seemed as if fortune had determined on the loss of the French, and Napoleon decided to retreat to the island of Lobau, where he felt sure that he could maintain his position, and secure supplies from the army on the right bank, until he had time to build bridges and unite his forces.