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In page Napoleonic Wars:

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The Austrians began the war by invading Bavaria on 8 September 1805 with an army of about 72,000 under Karl Mack von Leiberich,[6] and the French army marched out from Boulogne in late July 1805 to confront them.[citation needed] At Ulm (25 September – 20 October) Napoleon surrounded Mack's army, forcing its surrender without significant losses.