On the 17th of April, while at Donawerth, Napoleon commanded Davoust and Massena to march simultaneously towards a position in front, and then pushed forward the centre in person, to the same point. The Archduke Louis, who commanded the Austrian divisions in advance, was thus hemmed in unexpectedly by three armies, moving at once from three different points.
At Donawerth Napoleon addressed his troops in a proclamation in which he said: "Soldiers, the territory of the Confederation has been violated. The Austrian general expects us to fly at the sight of his arms, and to abandon our allies to him. I arrive with the rapidity of lightning. Soldiers, I was surrounded by you when the sovereign of Austria came to my camp in Moravia; you have heard him implore my clemency, and swear an eternal friendship towards me. Victors, in three wars Austria has owed everything to your generosity; three times has she perjured herself. Our past successes are a safe guarantee of the victory which awaits us. Let us march, and at our aspect may the enemy acknowledge his conqueror."
It should be remembered that at this time, while Napoleon was astonishing Europe by the rapidity of his movements, and the display of the resources of his military and political genius, he had left an army in the Peninsula, distributed over an immense space of territory, weakened by diseases, reduced by partial combats, and without receiving reinforcements from the interior of the Empire. During the whole of the German campaign of 1809, the French in Spain were merely able to maintain themselves in the positions they had occupied soon after Napoleon's departure.
Austria had reckoned on the absence of Napoleon and his Guard, and on the veteran troops of Marengo and Austerlitz being far distant. She knew that there did not remain more than 80,000 French scattered throughout Germany, while her army divided into nine bodies, under the orders of the Archduke Charles, had not less than 500,000 men.
The Archduke Louis was defeated and driven back at Abensberg on the 20th, and utterly routed at Landshut on the 21st, losing 9,000 men, thirty guns and all his stores. Those unfortunate Austrians who had been led from Vienna singing songs, under a persuasion that there was no longer a French army in Germany, and that they should only have to deal with Wurtemburgers and Bavarians, experienced the greatest terror when they came to conflict and found themselves defeated. The Prince of Lichtenstein and General Lusignan, were wounded, while the loss of the Austrians in colonels, and officers, of lower rank was considerable.
In the battle of Abensberg which occurred on the 20th, Napoleon was resolved to destroy the corps of the Archduke Louis, and of General Keller, amounting to sixty thousand men. The enemy only stood his ground for an hour and left eighteen thousand prisoners. The cannonade of the French was successful at all points and the Austrians, disconcerted by Napoleon's brilliant movements, beat a hasty retreat leaving eight standards and twelve pieces of cannon. The French loss was very small.
Before this engagement Napoleon saw defile before him on the plateau in front of Abensberg the Wurtemberg and Bavarian troops, allies of the French, who were going to put themselves in line and whom the pride of fighting under a general of his renown filled with enthusiasm. The Emperor caused them to be drawn up and proceeded to harangue them, one after the other, the officers translating his words to the troops. He said that he was making them fight, not for himself, but for themselves; against the ambition of the house of Austria, which was enraged at not having them, as of yore, under its yoke; that this time he would soon restore them peace, and forever, and with such an increase of power that for the future they should be able to defend themselves against the pretensions of their old dominators. His presence and words electrified his German allies, who were flattered to see him amongst them, he trusting entirely to their honor, for at that moment he had no other escort than some detachments of Bavarian cavalry.
When Napoleon arrived that evening at Rotterburg he was intoxicated with joy. The engagement, which was of short duration, had cost the Austrians 7,000 or 8,000 men, and he saw his adversary driven back on the Iser at the very beginning of the campaign, and the Austrian soldiers disheartened, like the Prussians after Jena.
The battle of Landshut completed the defeat of the preceding evening. On this day General Mouton, at the head of a column of grenadiers rushed through the flames that were consuming one of the bridges of the Iser; "Forward, but reserve your fire!" he shouted to the soldiers in a voice of thunder; and in a few moments he had penetrated into the town, which then became the seat of a sanguinary struggle, and which the Austrians were not long in abandoning.