Abensberg Archduke Charles sent orders to his brother Archduke Louis at 7:30 AM on 20 April. He instructed Louis to fall back to Rottenburg and defend behind the Große Laber. Charles intended Hiller to take position on Louis' left at
Pfeffenhausen. Charles erred in sending the orders so late and in not informing Louis of Hohenzollern's withdrawal to the east. The latter move left the V Armeekorps' right flank exposed. Pfanzelter held Bachl on the extreme right flank. To the west of Bachl, Thierry held Offenstetten with three and one-third battalions. His other two and two-thirds battalions had become separated the previous day and joined General-Major
Frederick Bianchi, Duke of Casalanza who had six battalions near Biburg. Louis posted Schustekh with 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. In one account, Lannes' advance guard approached Bachl in the late morning of 20 April, forcing Pfanzelter's small detachment from the Austrian III Armeekorps eastward. The 1st Bavarian Division under Lieutenant General
Crown Prince Ludwig of Bavaria and the 3rd Bavarian Division led by Lieutenant General
Bernhard Erasmus von Deroy, together with Demont's III Corps Division advanced on Offenstetten. Around 10:00 AM, they defeated Thierry's brigade, forcing him back on Bachl as Lannes approached from the north. Thierry hastily withdrew to Rohr, which he reached at 2:00 PM. Historian James R. Arnold offers a different narrative. He writes that Pfanzelter's command was withdrawn on the III Armeekorps commander Hohenzollern's orders, leaving the north–south road through Bachl wide open. Meanwhile, Thierry's attached dragoons discovered that Abensberg and its nearby roads were alive with moving columns of enemy troops. Around 8:00 AM, Thierry fell back on Bachl and found to his dismay that French cavalry already occupied the village. Having become separated from his supporting dragoons, Thierry's men were chased into the woods by Jacquinot's horsemen. From there the Austrians hiked cross-country toward Rohr. Author
Francis Loraine Petre states that Gudin encountered Pfanzelter north of Bachl and brushed him aside about 9:00 AM. The 1st Bavarian division and General-Major Hügel's Württemberg brigade drove Thierry from Offenstetten around 10:00 AM. When the Austrians reached Bachl they stumbled upon Jacquinot who attacked and they "scattered through the woods". Pfanzelter marched east to
Langquaid where he rejoined Hohenzollern's corps. Because he feared that the woods to his left might contain Austrians, Lannes slowed his march so he could scout the terrain to the east. Even so, his column arrived at Rohr before Thierry's infantry. Without Pfanzelter's detachment to warn him, the arrival of Lannes' column surprised Schustekh. The Austrian commander gamely threw four squadrons of hussars at Jacquinot's advance guard. Eventually, Jacquinot got his entire brigade into action and pressed the Austrian hussars back on the supporting battalion and one-third of
Grenz infantry south of Rohr. At this time, Thierry's winded infantry appeared on the scene. With the help of Gudin's 17th Light Infantry and a battery of artillery, Jacquinot's chasseurs broke Thierry's foot soldiers and hounded them into the woods again. To take the pressure off the infantry, Schustekh charged again, just as Thierry's lost dragoons showed up. At first, the attack went well, but then the Austrian horsemen came up against a mass of cuirassiers. The result was a rout of the Habsburg cavalry, who rode through the ranks of their own foot soldiers. The French chasseurs and cuirassiers rode roughshod over the troops of Thierry and Mesko, cutting down the fugitives. Over 3,000 Austrians became prisoners, including Thierry, and four cannon were lost. The previous evening, Hiller's VI Armeekorps bivouacked at Mainburg. Though a road ran directly from Mainburg to Louis' left flank at Siegenburg, a distance of only 13 kilometers, Hiller elected to join his colleague by a roundabout march via Pfeffenhausen. Once he arrived, Hiller was authorized to take command of all three left wing corps. Hiller personally arrived in Siegenburg to confer with Archduke Louis around midday. Hearing troubling reports from the right flank, he sent Feldmarschall-Leutnant
Karl von Vincent toward
Rottenburg with the line brigades of Generals-Major Josef Hoffmeister and Nikolaus Weissenwolf, plus four squadrons of the
Rosenberg Chevauxlegers Regiment # 6. Petre names the two line infantry brigade commanders. Archduke Louis posted Prince Reuss and General-Major
Joseph Radetzky von Radetz with four battalions and 12 cavalry squadrons at Siegenburg. Bianchi held the east bank of the Abens opposite Biburg. Lieutenant-General
Karl Philipp von Wrede probed at Siegenburg but his 2nd Bavarian Division was easily fended off by Radetzky and a battery of 12-pdr cannon. At this time, Louis heard that the French attacked Thierry, so he ordered Radetzky to send two battalions to the right flank and called up Kienmayer's command from Ludmannsdorf. Wrede moved north to Biburg, where he tried to get across the Abens again. At first he was not successful, but Bianchi withdrew to
Kirchdorf, allowing the 2nd Bavarian Division to cross to the east bank of the stream. Meanwhile, General of Division
Dominique Vandamme's Württemberg contingent (later known as the VIII Corps) replaced Wrede in front of Siegenburg. Vandamme soon realized that crossing at Siegenburg was futile, so he too marched north, crossed the river at Abensberg and moved south to Kirchdorf. Here the Bavarians and Württembergers found Bianchi with his reinforced brigade and a cavalry squadron. Reuss soon arrived with Radetzky's two battalions. Around 2:00 PM a sharp combat took place after which the Austrians retreated to the southeast. According to one account, General of Division
Jean Victor Tharreau's cavalry of the II Corps also became involved at Kirchdorf. Pressed by Wrede's Bavarian 7th Infantry Regiment, plus two of Hügel's Württemberg battalions, Radetzky conducted an orderly retreat on the Siegenburg road, covered by the grenzers and Kienmayer's grenadiers under General-Major
Konstantin Ghilian Karl d'Aspré. He managed to shepherd the V Armeekorps trains safely through Pfeffenhausen before the Bavarians cut him off. Wrede pursued aggressively and scooped up many prisoners but failed to capture the bridge, which the Austrians burned. Even so, the Bavarians kept up the pressure, crossing the shallow Große Laber at 11:00 PM to attack. Radetzky fell back to a hill called the Hornbach where his rear guard skirmished with the Bavarians into the early morning hours. When Vincent's column neared Rottenburg, he found the road jammed with the III Armeekorps trains. A charge by the
Rosenberg Chevauxlegers halted the French cuirassiers long enough for his infantry to gain solid positions on the east side of the Große Laber. Hiller arrived at Rottenburg in the late afternoon and ordered a counterattack at 7:00 PM. Vincent swung his left brigade forward and quickly overran a Bavarian unit, capturing 300 troops. Soon after, the
Deutschmeister Infantry Regiment # 4 got into a vicious firefight with Bavarian and French infantry. In the twilight, the Austrians were forced back by superior numbers with 600 casualties, but they had finally stopped their enemies.
Regensburg On 20 April, the Austrian II Armeekorps continued attacking Colonel Louis Coutard's 65th Line Infantry Regiment at Regensburg. A French convoy sent to replenish the 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 after which he promised to surrender if not relieved. The Austrian commander foolishly agreed to the terms. However, Liechtenstein's column soon appeared from the south. Liechtenstein pointed out that the existing truce did not apply to him and demanded an immediate surrender. Coutard thereupon capitulated 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. During the struggle the French captured 75 troops and one color, all of which were recovered. When Kollowrat finally reported the II Armeekorps available for duty that evening, the headquarters ordered his troops to make an overnight march west to
Hemau on the north bank of the Danube. In the morning, the tired troops were recalled to Regensburg from their pointless ramble. ==Aftermath==