Battle of Abensberg

• 1. Strategic Context And Setup

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  On the 10th of April 1809, Archduke Charles led his army across the Inn River and into the Kingdom of Bavaria. This invasion placed the forces of France and their German allies in grave danger within days. The Austrian host took six days to march from the frontier to the Isar River, moving slowly but effectively. Napoleon's deputy commander Marshal Louis Alexandre Berthier mismanaged the Grande Armée's concentration during this critical window. Units scattered across a broad front left the French position confused and vulnerable. The central mass of Archduke Charles' 209,600-man host crossed the Isar at Landshut on the 16th of April. Emperor Napoleon arrived at the front from Paris the next day to wrest control back from the archduke. He consolidated his forces and ordered Marshal André Masséna's IV Corps to march on Landshut. General of Division Nicolas Oudinot's II Corps also moved to cut the Austrian line of communications. Napoleon planned for Marshal François Joseph Lefebvre's Bavarian VII Corps to hold the center at Abensberg while Davout's left flank III Corps withdrew west. This withdrawal aimed to escape being trapped between Charles' main body and the Danube river.

• 2. Tactical Deployment And Forces

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  Archduke Louis spread out his V Armeekorps behind the Abens River facing west on the morning of the 20th of April. Only the divisions of Feldmarschall-Leutnants Prince Heinrich XV of Reuss-Plauen and Vincenz Freiherr von Schustekh-Herve remained under Louis' command after detachments. Feldmarschall-Leutnant Michael von Kienmayer's II Reserve Armeekorps waited in support at Ludmannsdorf with a nominal strength of 7,975 men. The bulk of Hiller's VI Armeekorps reached Mainburg to the south by the evening of the 19th. Official returns showed Hiller's three corps totalled 75,880 troops but detachments reduced the left wing to only 42,000 soldiers. Napoleon mistakenly assumed the bulk of Archduke Charles' army lay directly in front of him that morning. He ordered a drive southeast toward Landshut instead of attacking the actual Austrian position. Lannes received orders to turn the Austrian right flank by pushing south toward Rohr. General of Division Dominique Vandamme would attack Siegenburg with his small Kingdom of Württemberg corps. Lefebvre's other VII Corps divisions linked Lannes and Vandamme while Masséna's IV Corps captured Landshut.

• 3. The Lannes Breakthrough At Rohr

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  Lannes' advance guard approached Bachl in the late morning of the 20th of April forcing Pfanzelter's small detachment eastward. Around 10:00 AM French forces defeated Thierry's brigade near Offenstetten and forced him back on Bachl as Lannes approached from the north. Thierry hastily withdrew to Rohr reaching it at 2:00 PM. The Austrian commander Schustekh posted four squadrons of hussars and one and one-third battalions at Rohr. Schustekh's infantry had just rejoined V Armeekorps after marching from Mainburg with General-Major Joseph, Baron von Mesko de Felsö-Kubiny's detachment. Jacquinot attacked Schustekh's hussars pressing them back on the supporting battalion and one-third of Grenz infantry south of Rohr. Thierry's winded infantry appeared on the scene but Gudin's 17th Light Infantry broke their foot soldiers. Schustekh charged again just as Thierry's lost dragoons showed up to support him. The Austrian horsemen came up against a mass of cuirassiers resulting in a rout of the Habsburg cavalry. They rode through the ranks of their own foot soldiers while French chasseurs and cuirassiers cut down fugitives. Over 3,000 Austrians became prisoners including Thierry and four cannon were lost.

• 4. Siegenburg And The Left Wing Collapse

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  On the 20th of April the Austrian II Armeekorps continued attacking Colonel Louis Coutard's 65th Line Infantry Regiment at Regensburg. A French convoy sent to replenish critically low ammunition supply was ambushed by Austrian cavalry at 8:00 AM. The French troops finally ran out of ammunition and Coutard asked Kollowrat for a 24-hour truce. He promised to surrender if not relieved within that time frame. The Austrian commander foolishly agreed to the terms allowing the French to regroup briefly. However Liechtenstein's column appeared from the south pointing out the existing truce did not apply to him. He demanded an immediate surrender forcing Coutard to capitulate at 5:00 PM. The French sappers had found it impossible to demolish the sturdily-built Regensburg bridge. The intact bridge later played a key factor in the escape of Charles' army. In two days of fighting the French lost 11 officers and about 200 soldiers killed and wounded plus 1,988 captured. Austrian losses were 73 dead 220 wounded and 85 missing for a total of 378 casualties.

  That evening as the extent of Thierry and Schustekh's disaster became known Hiller resolved to pull his

• 5. The Regensburg Capitulation

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  three corps behind the Isar at Landshut. This crucial decision meant the Austrian left wing would operate independently from Archduke Charles' main body. Hiller would only reunite with his army commander on the 15th of May north of Vienna. While Napoleon savaged his left wing Archduke Charles remained amazingly inert during the battle. At 6:00 AM the archduke was with Prince Rosenberg and at 7:30 AM he sent orders to Archduke Louis. But from 11:00 AM until 6:30 PM the Austrian generalissimo failed to issue any orders. He either became obsessed with capturing Regensburg or had an epileptic seizure locking himself in his quarters. The Austrian III IV and I Reserve Armeekorps did not disturb Davout's remaining three divisions under Generals of Division Louis Friant Saint-Hilaire and Montbrun on the 20th of April. Despite being outnumbered Napoleon's 113,000 troops split the 161,000 strung-out Austrians into two forces.