On this day in 1805, Austrian General Mack surrendered to Napoleon at Ulm. This action concluded the Ulm Campaign, in which a 72.000 strong Coalition army expecting minor French forces was encircled by 235.000 French and Bavarians.

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  1. The disaster at Ulm was primarily the result of faulty assumptions on the part of the Coalition of Napoleon’s plans and capabilities, based on a study of Napoleon’s past campaigns.

    **Coalition plans**

    In 1796-1797 and in 1800, Napoleon’s personal campaigns had been generally limited to northern Italy (excepting Egypt). The Coalition military planners therefore expected the war to be decided in Italy, and sent the best Austrian army of 100.000 under Archduke Charles into Italy, where they would be buoyed with further forces from Naples, as well as British and Russian forces landing on the peninsula. A secondary army of 72.000 Austrians would be sent to Germany to contain any French offensives there, with a further 23.000 further Austrians guarding the passes between the Alps connecting the two armies. 100.000 Russians were also steadily marching in by land from the east.

    Napoleon’s method of war had also been studied, and the Austrian army had been reformed. General Mack, when marching his 72.000 Austrians into Germany had cut down on supply trains and intended to make up the deficiency by living off the land, as Napoleon had famously done in his previous campaigns. This however had deletrious consequences on the 72.000 Austrians, approximately twice as large as the armies Napoleon had commanded in Italy and Egypt, and being limited by their march (imagine soldiers at the front foraging all the food near the path of march, leaving the men in the back to either go further to forage or skip a meal), quickly foraged the land barren. The Austrians in Germany became disorganized by lack of provisions, foraging, and forced marches, and in observation of the sad state his army was in, Mack believed there was little threat of large French forces crossing the Rhine, for they would supposedly meet the same problem.

    **Napoleon’s plans**

    In 1800, Napoleon had suggested to General Moreau a strategic plan of linking up his army in Germany with Napoleon’s Army of the Reserve. This would create a local superiority in numbers for French forces to defeat the Coalition in Germany, after which Napoleon wanted the combined French army to cross into Italy and defeat the remainder of the Coalition. Moreau rejected this plan, and Napoleon went back to the drawing board to create the Marengo campaign. That winter, Moreau won the Battle of Hohenlinden, which set him up as a possible rival to Napoleon, and both royalists and republicans began rallying around Moreau. Napoleon seized on these events to condemn Moreau as a conspirator, and Moreau was placed on trial. In a classic Napoleonic political manuever, Napoleon pressured the judges behind the scenes to sentence Moreau to a harsh imprisonment, before intervening publically as First Consul to reduce Moreau’s sentence to exile. The opposition that had rallied around Moreau to oppose Napoleon was humiliated by their symbol becoming “indebted” to Napoleon, while Moreau was denied matryrdom and removed as a political threat. By exile, bribing people out of political power, or persuading them onto his side, Napoleon had outmanuevered all his domestic rivals without reigniting the national trauma of domestic mass murder from the Reign of Terror and the Thermidorian Reaction. From then on his word was absolute, and he would do as he pleased.

    With his absolute power, Napoleon reorganized the French army into the corps system, a system of independent armies (called corps) with their own cavalry, artillery, and infantry. These armies were placed within a days’ march of one another, and large enough that if any one of them met a superior enemy force they could be expected to stall for 24 hours while the armies around it converged, transforming initial numerical inferiority into parity or superiority. He amassed 200.000 men on Boulogne where he trained them for 2 years in the new system. This training in itself was unusual for the time, as apart from Prussia and Russia, most nations would not be constantly drilling a massive standing army until an active campaign was expected, generally leaving their forces to languish in garrisons or discharged when not on campaign. The result was that once the rest of Europe formed up their armies, the French army had been in a constant state of battle-readiness for two years.

    Napoleon’s grand strategy for the war was entirely different from what the Coalition had anticipated. He would send a minor force into Italy, while he turned the mass of his 200.000 men into Germany to crush the Coalition forces there, which he saw as the main theater of the war. The French forces in Italy would be there only to tie down the Coalition, and he believed any French loss in Italy would be strategically useless in the face of a French victory in Germany. An order to the army he placed in Naples reads: “The enemy could be at Milan, and you should nevertheless remain in Naples, because the enemy’s success, if he attains any, will be only of short duration and an ephemeral chimera.”

    Napoleon had little accurate intelligence on the Coalition dispositions, and spent most of August haranguing his spies to do better, the intelligence reports he received overestimating the Austrian army as being twice the size it actually was. Mack’s rapid advance into Germany had further disoriented Napoleon, who had hoped to unite with his Bavaria ally in central Germany. He told Talleyrand: “I would not have believed the Austrians so determined, but I have been fooled so many times I do not blush about it.” Towards the end of September however, he had gotten more comfortable with what to trust and what to ignore. According to Frederick Kagan, “He stopped issuing insistent calls for more intelligence and started making the cryptic and self-satisfied remarks for which he is famous.” The French army started crossing the Rhine on 25 September.

    **The Campaign**

    Mack’s expectations of logistical difficulties would have been correct if he had been facing the same French army Napoleon had commanded in 1796. Under the corps system, Napoleon allowed each corps an independent line of march and assigned each corps their own area of forage. While Mack expected a French army to march on roughly the same area, Napoleon had instead invaded Germany across a massive front of 160 kilometers. Under classical principles of war, this left Napoleon’s forces open to defeat in detail, but the French had just spent the last two years being drilled not only tactically but in corps-level maneuvering, and a threatened corps knew how to stall defeat by superior forces for its friends to come to its aid.

    Napoleon placed a small contingent of cavalry in the Black Forest to dance before Mack’s position at Ulm, while the French army in the north swung around the Austrians in a wide wheeling maneuver. By 5 October, the French had crossed the Danube behind Mack’s position at Donauwörth. In response, Mack ordered a counterattack on Napoleon’s lines of communication, but this was thwarted by French seizure of the bridges at Günzburg. Mack retreated back to Ulm, contemplating what to do. Napoleon meanwhile ordered his corps to seize the bridges around Ulm. Mack attempted to break out in a northern drive, which came to grief on 14 October at Elchingen. On the same day, a French corps had landed south of the Austrian position, meaning the Austrian army was now well and truly encircled. At this point the Archduke Ferdinand broke with Mack and unilaterally evacuated all the cavalry from Ulm to break out and join with an Austrian detachment further north at Heidenheim. They successfully broke out of the encirclement around Ulm to reach their compatriots at Heidenheim, where they both surrendered to the second line of the French encirclement. On 20 October, Mack finally surrendered his main force at Ulm. Overall, the Austrians had lost 60.000 out of an army of 72.000, compared to French losses of 2.000.

    Visualization of the Ulm Campaign:

    [Napoleon concentrates his army on the Rhine, 2-25 September](https://upload.wikimedia.org/wikipedia/commons/a/ac/Ulm_campaign_-_Invasion_of_Bavaria_and_French_assembly_on_the_Rhine%2C_2-25_September_1805.jpg)

    [Napoleon crosses the Rhine and falls on the Danube, 26 September-09 October](https://upload.wikimedia.org/wikipedia/commons/4/4e/Ulm_campaign_-_French_strategic_envelopment%2C_26_September-9_October_1805.jpg)

    [Napoleon cuts the Austrians off from the Russians, weaves an encirclement around Ulm](https://upload.wikimedia.org/wikipedia/commons/1/13/Ulm_campaign_-_Engagements_around_Ulm%2C_11-14_October_1805.jpg)

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