What treaty did Austria sign in the War of the Third Coalition ?
The war would be decided on the continent , and the major land operations that sealed the swift French victory involved the Ulm Campaign , a large wheeling manoeuvre by the Grande Armée lasting from late August to mid-October 1805 that captured an entire Austrian army , and the decisive French victory over a combined Russo - Austrian force under Tsar Alexander I at the Battle of Austerlitz in early December .