The combat of Michelberg (16 October 1805) saw the French push the Austrians out of a key position outside Ulm, making the surrender at Ulm of 20 October almost inevitable.
At the start of the War of the Third Coalition the Austrian army under General Mack advanced west along the Danube into Bavaria, eventually ending up at Ulm. At the same time Napoleon's army crossed the Rhine, swept through Germany and reached the Danube to the east of the Austrian positions, all without being discovered. The French then advanced west towards Ulm, in the expectation that Mack would attempt to break out along the south bank. In fact Mack never attempted to move south of the Danube, instead making his move in the north. A first attempt escape was held up by a small French force at Albeck (11 October 1805).
Mack's most serious attempt at a breakout came on 13-14 October, when two columns were sent north-east. By 14 October the right-hand column had reached Elchingen, where it was defeated by Marshal Ney, who had been ordered to cross to the north bank of the Danube (battle of Elchingen, 14 October 1805). While the left-hand column temporarily escaped to the north, the survivors of the right-hand column retreated to Ulm. The Austrians were now almost pinned into Ulm, but they did still have positions on the Michelberg, a hill just to the north of Ulm, and the Frauenberg.
On 16 October (15 October in some sources) Ney's corps stormed the Michelberg, while Lannes took the Frauenberg. The Austrians were now trapped in the city. On 17 October Mack and Napoleon's emissary de Ségur agreed that the Austrians would surrender on 25 October if no relief came, but eventually the demoralised Austrians surrendered early, on 20 October. Napoleon was now free to move east to deal with the Russians and the remaining Austrians.