 This huge mass of maneuver wheeled to the south and crossed the Danube River to the east of (i.e., behind) General Karl Freiherr Mack von Leiberich's concentration at Ulm.Unaware of the force bearing down on him, Mack stayed in place as Napoleon's corps spread south across the Danube, slicing across his lines of communication with Vienna.Murat's advance guard included the heavy cavalry divisions of General of Division Louis Klein (16 squadrons of the 1st, 14th, 20th and 26th Dragoon Regiments) and General of Division Marc Antoine de Beaumont (18 sqdns.