The battle of Elchingen (14 October 1805) saw the French fight their way from the south to the north bank of the Danube, making up for a misjudgement on Napoleon's part and also thwarting an Austrian attempt to escape from Ulm.
At the start of the War of the Third Coalition the main Austrian army, under General Mack, advanced west along the Danube into Bavaria, ending up at Ulm. At the same time Napoleon crossed the Rhine, slipped past the Austrians without being discovered and reached the Danube well to Mack's east. At this point Napoleon made his mistake, assuming that Mack would attempt to break out of the trap by advancing east along the south bank of the Danube. This would have allowed the Austrians to keep in contact with their armies in the Tyrol and if successful would have enabled Mack to protect Vienna. With this in mind most of the French army moved onto the south bank of the Danube. Only Ney's corps was to stay on the north bank. Ney, Murat and Lannes were to advance west towards Ulm, with Murat and Lannes on the south bank. Murat was given command of these three corps, although Napoleon accompanied the final advance.
Mack didn't react in the way Napoleon had expected. Most of the Austrian army was on the north bank of the Danube (as was Ulm), and the move to the south bank confused Mack. He then convinced himself that Napoleon was trying to retreat back to France and was planning to move past Ulm on the opposite side of the river. Mack prepared to attack the retreating French, but in the meantime kept most of his troops on the north bank.
As Murat moved west he decided that he needed Ney's men on the south bank. Eventually Ney convinced him to leave one division on the north bank, so for several day's Dupont's division of Ney's corps was the only major French unit preventing the Austrians from escaping from Napoleon's trap by moving along the north bank of the Danube.
The scale of Napoleon's error became clear over the next few days. On 11 October Mack finally decided to make his move. As a result Dupont's division found itself facing an Austrian column 25,000 strong (battle of Albeck, 11 October 1805). Despite being outnumbered Dupont managed to hold on all day, before retreating after dark. Mack's escape route was effectively clear, but he also chose to retreat, returning to Ulm.
The Austrians rested on 12 October, while Napoleon waited for news of the Russians coming from the east. When he discovered that they were 180 miles away he was free to turn all of his attention west. On 12 October six French corps advanced west on the south side of the Danube heading towards Ulm, and a battle that Napoleon expected to take place on the River Iller. On 13 October the Austrians finally made their move, but it wasn't what Napoleon expected. Two Austrian columns left Ulm, both on the north bank of the river. The left-hand column approached Dupont's position, while the right-hand column reached Elchingen, seven miles east of Ulm on the Danube, where they prepared to destroy the river bridge. By now Napoleon had realised that the Austrians weren't where he expected them to be. Ney and Murat were ordered to cross to the north bank of the Danube, where they would complete the encirclement of Ulm.
The brunt of the fighting fell on Ney's corps, which came up against 15,000 Austrians under Feldmarschalleutnant Graf von Riesch. The Austrians were holding the town of Ober-Elchingen, on the north bank of the Danube, and had troops on the south bank, leaving the bridge partially demolished in order to give them a way to retreat.
Modern Elchingen is split into three. Oberelchingen and Unterelchingen are on the north bank of the Danube, with Oberelchingen to the west and Unterelchingen to the east. A small community just called Elchingen is on the south bank, but this doesn't appear on 19th century maps of the area. The Danube is a short distance south of Oberelchingen.
The fighting began at around 8.20am when the 39th Line attacked the Austrians on the south bank and was repulsed. Ney then outflanked this first Austrian line and the two infantry regiments holding it retreated. The 69th Line attacked the new position but was repulsed, although an Austrian cavalry counterattack also ended in defeat.
The French finally cleared the south bank in an assault that began at around 10am. The Austrians retreated across the river, but instead of destroying the bridge they decided to try and lure part of the French force across so they could defeat it piecemeal. This succeeded at first, but it also infuriated Ney who took personal command of the efforts to repair the bridge and was one of the first to cross to the north bank. In the fighting that followed Ney's men captured two Austrian infantry regiments and drove the rest of the Austrian force back towards Ulm.
Further north the second Austrian column, under Werneck, was attacking Dupont's men close to Albeck. The French were close to defeat here when Ney's men arrived on the scene. Werneck was forced to abandon the fight and retreated to the north. He was later joined by a cavalry force under the Archduke Ferdinand, but was closely pursued by Murat and was forced to surrender at Heidenheim on 19 October.
This victory ended any realistic chance of an Austrian escape. Two days later Ney's corps pushed the Austrians off the Michelberg, just to the north of Ulm. Mack negotiated an armistice in which he agreed to surrender on 25 October unless relieved, but eventually surrendered five days early, on 20 October.