The campaign in the upper Danube valley had begun in October, with several clashes in Swabia.

Mack has decided, unwisely, to defend Ulm, instead of trying to escape the approaching French army.

Mack reacts by sending Feldmarschall-Leutnant Franz Xavier Auffenberg with only six thousand men to stop the French.

Near the Bavarian town of Wertingen, forty kilometers (twenty-five miles) northwest of Augsburg, on October 8 the 1st Regiment of dragoons, part of Murat's Reserve Cavalry Corps, and grenadiers of Lannes' V Corps surprise an Austrian force half its size.

The Austrians are arrayed in a line and unable to form their defensive squares quickly enough to protect themselves from the four thousand dragoons and eight thousand grenadiers.

Murat and Lannes crush the hapless Auffenberg at the Battle of Wertingen, inflicting losses of four hundred killed and wounded on the Austrians and capturing twenty-nine hundred soldiers and six cannons.