Ulm, Battle of

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The Battle of Ulm (September–October 1805) was the opening round of the War of 1805, fought between Napoleon I and the Third Coalition of Austria, Russia, Britain, and Sweden. The conflict arose primarily from conflicts between Napoleon, Russia, and Austria over measures Napoleon had taken both to secure his own position in France and to strike at Great Britain, with which he had been at war since March 1803. The immediate sources of conflict in 1805 were in Italy, a fact that played an important role in shaping the military campaign.

The allied war plan for the late summer of 1805 involved a coordinated effort: vast armies attacking France from the Adriatic to the North Sea. The largest Austrian army, commanded by Archduke Charles, would attack in Italy. Another Austrian force, nominally commanded by Archduke Ferdinand but actually controlled by its quartermaster general, Baron Karl von Mack, would seize Bavaria and await the arrival of Russian reinforcements commanded by General Mikhail Kutuzov before invading France via Switzerland. Still other forces were to make landings in Naples and Hanover, while large Russian armies attempted to compel Prussia to join the coalition as well.

Napoleon did not initially recognize the gathering storm clouds. He was intent upon his plans for the invasion of England and the final preparations of the Army of the Channel at Boulogne with which he intended to destroy his ancient nemesis. The emperor also believed that he had sufficiently cowed Austria during the War of the Second Coalition (1798–1801) that he need not fear it in 1805. When he learned in late August that the French fleet would not be able to seize the English Channel to permit his invasion of England, Napoleon decided to strike the coalition instead, hoping that by punishing Austria he could gain time to renew his war with "perfidious Albion."

He therefore directed the bulk of the newly rechristened "Grande Armée" to race from its camps along the Channel to the Rhine, while the corps of Marshal Jean-Baptiste Bernadotte, which was occupying the British territory of Hanover, would rush south, through Prussian territory, toward the Upper Danube. At first, Napoleon did not know what the Allies' intentions were. He sought only to drive into Bavaria as rapidly as possible to protect or, if necessary, restore his ally, Maximilian I, the elector of Bavaria, to his threatened throne. The emperor's initial war plan, therefore, would have precipitated a head-on collision with the advancing Austrian army. As the Grande Armée approached its final positions on the Rhine in late September, however, Napoleon realized that Mack's Austrian army had advanced all the way to the Iller River, far to the west. He saw a corresponding opportunity to drive into Mack's rear and cut his army off from its lines of communication and retreat. Adjusting his plans of movement accordingly, Napoleon enveloped Mack's right flank.

The success of that maneuver hinged on the movement of Bernadotte's corps (and two others) through the Prussian territory of Ansbach, while the Prussians had declared themselves in a state of armed neutrality. Mack did not expect or believe that Napoleon would violate Prussian neutrality, and thereby risk bringing more than 200,000 first-rate troops into the field against him. Mack had therefore taken no steps to guard his right wing, enabling Napoleon's forces to drive rapidly into Mack's rear and force the Austrians back toward Ulm in a series of confused battles along the Danube. By 14 October, the Austrians were sealed in the dilapidated fortress of Ulm itself, ringed by French troops and with no hope of escape. Mack agreed on 17 October to surrender his army by the twenty-fifth, although the date was subsequently moved up to the twentieth at Mack's request.

Napoleon's violation of Prussian territory had, in the meantime, had the effect of bringing Prussia into the war. At Potsdam in early November, King Frederick William III signed an agreement with Tsar Alexander I of Russia to strike Napoleon's exposed army along its flanks and rear. The Prussians began a rapid mobilization and deployment to effect this plan, which was suspended by the Treaty of Schönbrunn signed by Prussian co-foreign minister, Count Christian von Haugwitz, on 15 December, thirteen days after the Battle of Austerlitz at which Alexander and his remaining Austrian allies were defeated.

The Battle of Ulm was not a masterpiece of prior planning and skillful deception, as it is sometimes made out, but rather a masterpiece of skillful and decisive adaptation to changing circumstances. Napoleon's initial plans were to do more or less what Mack expected him to do, although with much greater force. He devised the plan for the final, brilliant maneuver only after he had seen the Austrian deployment. He thereby seized an opportunity that a confused enemy had presented to him. Moreover, Napoleon was able to do so only by sacrificing the future security of his army. He had not reckoned on Prussian hostility following the violation of Ansbach, and so did not understand the full danger to which he exposed his army at a strategic level in order to gain an operational advantage over the enemy at hand.

See alsoArmies; Austerlitz; French Revolutionary Wars and Napoleonic Wars; Napoleon.


Duffy, Christopher. Austerlitz, 1805. London, 1977.

Frederick W. Kagan