of other generals throughout his career. On 18 June 1805 he was present at the Battle of Blanc-Nez and Gris-Nez after joining a Batavian flotilla, headed for Boulogne, as an observer. As commander of the III Corps of the Grande Armée, Davout rendered his greatest services. At the Battle of Austerlitz, following a forced march of 48 hours to fall on the left flank of the Russian army, the III Corps bore the brunt of the allies' attack. In the subsequent War of the Fourth Coalition, Davout, with a single corps, with the intention to fall on the Prussian left wing, fought and won the Battle of Auerstädt against the main Prussian Army, under the Duke of Brunswick, which had more than twice as many soldiers at its disposal (more than 63,000, to Davout's 28,000). Historian François-Guy Hourtoulle writes: "At Jena, Napoleon won a battle he could not lose. At Auerstädt, Davout won a battle he could not win". As a reward, Napoleon let Davout and his men enter Berlin first on 25 October 1806. Davout added to his renown in the battles of Eylau and Friedland. Napoleon left him as governor-general of the newly created Duchy of Warsaw following the Treaties of Tilsit in 1807, and the next year awarded him with the title of Duke of Auerstädt. During the War of the Fifth Coalition in 1809, Davout took part in the Battle of Eckmühl, and also distinguished himself in the Battle of Wagram, where he commanded the right wing. He was later made Prince of Eckmühl following the campaign. In 1810 Davout travelled to Compiègne with Napoleon to collect the 18-year-old bride Marie-Louise of Austria. Davout was entrusted by Napoleon with the task of organizing the "corps of observation of the Elbe", which would become the gigantic army with which Napoleon invaded Russia in 1812. In this, he commanded the I Corps, the strongest corps, numbering over 70,000. On 1 July he left Vilnius. On the order of Napoleon Davout secretly took over the command Jérôme Bonaparte, occupied Minsk but had lost a third of his men due to sickness and desertion. He defeated the Russians at Mohilev before he joined the main army at Smolensk, with which he continued throughout the campaign. During the retreat from Moscow he conducted the rear guard, which was deemed too slow by the emperor, and was replaced by Marshal Michel Ney