Wartensleben and Charles united first, and the tide turned against the French. With 25,000 of his best troops, the Archduke crossed to the north bank of the Danube at Regensburg and moved north to join his colleague Wartensleben. The defeat of Jourdan's army at Amberg, Würzburg and Altenkirchen allowed Charles to move more troops to the south. The next contact occurred on 19 October at Emmendingen, in the Elz valley which winds through the Black Forest. The section of the valley involved in the battle runs southwest through the mountains from Elzach, through Bleibach and Waldkirch. Just to the southwest of Waldkirch, the river emerges from the mountains and flows northwest towards the Rhine, with the Black Forest to its right. This section of the river passes through Emmendingen before it reaches Riegel. Riegel sits in a narrow gap between the Black Forest and an isolated outcropping of volcanic hills known as the Kaiserstuhl. Here the archduke split his force into four columns.