[Ennath]

April 22, 1809
Battle of Eckmühl

In the early morning of April 10, 1809, the War of the 4th Coalition opened as leading elements of the Austrian army, under Archduke Charles, crossed the Inn River and invaded Bavaria. Bad roads and freezing rain slowed the Austrian advance, but the outnumbered Bavarians gradually retreated. The Austrian attack occurred about a week before Napoleon anticipated, and in his absence Berthier's role became all the more critical. Berthier (whose fortè was staff work) proved to be an insufficient field commander, a characteristic made worse by the fact that several messages from Paris were being delayed and misinterpreted when they finally arrived. Napoleon had written that an Austrian attack before April 15 should be met by a general French concentration around Donauwörth and Augsburg, Berthier focused on a sentence that called for Davout to station his III Corps around Regensburg and ordered the Iron Marshal to move back to the city despite massive Austrian pressure.

The “Grand Army of Germany” was now in a perilous position of two wings separated by 75 miles, linked by a thin cordon of Bavarian troops. On the 16th, the Austrian advance guard had beaten back the Bavarians near Landshut and had secured a good crossing place over the Isar by evening. Napoleon finally arrived in Donauwörth on the 17th after a furious trip from Paris. Archduke Charles congratulated himself on a successful opening to the campaign and planned to destroy Davout's and Lefebvre's isolated corps in a double-pincer. When Napoleon realized that significant Austrian forces were already over the Isar and were marching towards the Danube, he insisted that the entire French army deploy behind the Ilm River within 48 hours, all in hopes of undoing Berthier's mistakes and achieving a successful concentration. However, he underestimated the number of Austrian troops heading for Davout; Napoleon believed Charles only had a single corps over the Isar, but in fact, the Austrians had five corps, a grand total of 80,000 men. Napoleon needed to do something quickly to save his left flank from collapsing.

Davout anticipated the problems and withdrew his corps from Regensburg, leaving a garrison of only 2000. The northbound Austrian columns in the Kelheim–Abbach zone ran into the French columns heading west towards Neustadt in the early hours of the 19th. The Austrian attacks were slow, uncoordinated, and easily repulsed. Napoleon knew there was fighting in Davout's sector and had already devised a new strategy: while the Austrians attacked to the north, Masséna's corps, later augmented by Oudinot's forces, would strike southeast towards Freising and Landshut in hopes of rolling up the entire Austrian line and relieving the pressure on Davout. Napoleon was reasonably confident that the joint corps of Davout and Lefebvre could pin the Austrians while his other forces swept the Austrian rear.

The attack on the 20th began well as the central Austrian V Corps guarding Abensberg gave way. However, Massena's advance towards Landshut required too much time, permitting Hiller to escape south over the Isar. The Danube bridge that provided easy access to Regensburg and the east bank had not been demolished, allowing the Austrians to transfer themselves across the river and rendering futile French hopes for the complete destruction of the enemy. The Austrians had lost 10,000 men and 30 guns, but were still a potent force. That evening, Napoleon realized that the day's fighting had only involved 2 Austrian corps. Charles still had a good chance of escaping east over Straubing if he wished.

Charles now moved to concentrate his remaining forces so as to envelop and destroy Davout's corps. Prince Friedrich of Hohenzollern-Hechingen's III Corps (15,700 men) and Prince Franz Seraph of Rosenberg-Orsini's IV Corps (21,400 men), were ordered to hold the Austrian left, pinning Davout's corps, while Johann Kollowrat's fresh II Corps (28,100 men) and the elite grenadiers and cuirassiers of Prince Johann of Liechtenstein's I Reserve Corps advanced south from Regensburg and deployed against Davout's exposed left flank. Inexplicably, no orders were issued to Count Heinrich von Bellegarde, so his powerful I Corps (27,600 men) remained on the north bank of the Danube and played no role in the subsequent fighting.

For his part, Napoleon was intent on enveloping and destroying the Austrian forces retiring southwest to Landshut. The II and IV Corps (57,000 men under the overall command of Marshal Masséna) were directed to cross the Isar upstream from Landshut and block the Austrians from crossing to the South Bank. Meanwhile, under the overall command of Marshal Lannes, Lannes' Provisional Corps, the VII (Württemberg) Corps, a division from VII Corps and two cuirassier divisions (51,000 men) were to closely pursue and destroy the defeated Austrians. The mop-up was left to Davout, even though more than half of the III Corps' original units had been detached to create Lannes' task force. Despite Davout's reports to the contrary, Napoleon ordered him to attack the Austrians on his front in the morning, with the proviso that Lefebvre's equally depleted corps would support him if he needed help (A total of approximately 36,000 men for both corps).

Leading elements of the Austrian attack ran into Montbrun's cavalry, who managed to reduce the impetus of the charge thanks to hilly and wooded terrain. Rosenberg displayed serious concern when he realized that Davout's troops were not moving to account for the ongoing battle, and rightly assumed that more French troops were on the way. These troops had, in fact, arrived and brushed aside Rosenberg's flank guard. Napoleon had set the French army into motion around 2 a.m. on the 22nd and had his men march 18 miles north in just a few short hours, meaning reinforcements for Davout would be arriving faster than promised.

The vanguard of the assault were the German troops under Gen. Vandamme, who stormed the bridge at Eckmühl and even captured the town's chateau after ferocious Austrian resistance. At this point, Davout launched his men against the Austrian center at the village of Unterlaichling and the woods to the north. The 10th Legere Regiment became involved in vicious fighting around the woods, but eventually was strengthened by Bavarians and managed to capture the positions. North of Unterlaichling, Davout's troops under Louis Friant and St. Hilaire steadily pushed back the defenders of Oberlaichling and the surrounding woods, overran a redoubt held by Hungarian grenadiers, and prompted Charles to order a general retreat.

The struggle now devolved into a series of major cavalry clashes as the Austrians attempted to extricate their army without losing too many prisoners. Perhaps the best cavalry in the Habsburg army, the Vincent Chevau-légers and the Stipsic Hussars, occupied the Bettelberg ridgeline between Eckmühl and the woods above Unterlaiching. These elite units demolished some German light cavalry before being stopped by Bavarian infantry. Napoleon was insistent on the immediate capture of this position and ordered forward two heavy cavalry divisions under St. Sulpice and Nansouty. These horsemen were pummeled by Austrian artillery but came on nonetheless and managed to saber the gunners after having seen off the enemy cavalry.

The first phase of the retreat ended, but it was not over yet. The Austrians had found a chokepoint in the road and were instructed to stem the French tide. Three French cuirassier divisions supported by additional German light cavalry attacked and a swirling melee developed. The Austrians fought heroically but were heavily outnumbered and had to retreat. During this part of the conflict, more French cavalry struck their flank and the remaining Austrian horse fled north to Ratisbon (Regensburg).

The French had won the battle, but it was not a decisive engagement. Napoleon had hoped that he would be able to catch the Austrian army between Davout and the Danube, but he didn't know that Ratisbon had fallen and thus gave the Austrians a means of escape over the river. Nevertheless, the French inflicted 12,000 casualties at the cost of just 6000, and Napoleon's speedy arrival witnessed an entire axial realignment of his army (from north-south to east-west) that permitted the defeat of the Austrians. Both sides prepared for the next day’s fighting.