Louis probably first followed the
Via Istrum on the right (south) bank of the
Danube towards Alemannia, where Adalbert would have guarded the road. Adalbert was probably stationed on the left (west) bank of the river
Lech, a southern tributary of the Danube. Louis would have crossed the Danube and headed north on the left (east) bank of the Wörnitz, effectively leaving three major rivers between himself and Adalbert. Learning of Louis's movements, Adalbert must have crossed the Danube and headed north on the opposite bank of the Wörnitz. The Ries contains numerous small rivers and streams that empty into the Wörnitz, which in turn flows into the Danube. Louis's intention was probably to force Adalbert to break up his army in many separate crossings, leaving him vulnerable to an ambush. This strategy is discussed in
Vegetius'
De re militari. The
Annales Iuvavenses record that the battle took place "across the river Wörnitz" (
ultra ripam Werinza). If this refers to the other side of the Wörnitz relative to Salzburg, where the annals were written, then it would seem that Louis crossed the river to surprise Adalbert. It is more likely, however, that Adalbert crossed to attack Louis. The battle took place on Friday, 13 May. Adalbert's forces were caught by surprise. They may have been ambushed in mid-crossing. According to the
Annales Bertiniani, Louis's forces charged, presumably following a volley of arrows: "Louis then hurled his men on the troops which Lothar had stationed to resist him, slew many of them and put the rest to flight." The
Annales Fuldenses record that Lothar's men, "arriving at the point of the lances", turned and fled. These contemporary reports indicate that Louis opened the fighting with a
cavalry charge. According to the
Annales Fuldenses, an "uncountable number of men" of Lothar were killed. Adalbert was among them. ==Aftermath==