Emperor Napoleon I of France thrust his 180,000-man army through the Frankenwald, winning the Battle of Schleiz on 9 October and the Battle of Saalfeld on 10 October. The Prussian high command concentrated their armies on the west bank of the Saale River. They planned for Brunswick to move north toward Halle, while Hohenlohe covered his eastern flank by defending at Jena. On 14 October, Brunswick's army ran head on into Louis Davout's III Corps near Auerstedt and was badly defeated. Meanwhile, Napoleon fell on Hohenlohe at the Battle of Jena with the bulk of his army. Rüchel had been told to stay at Weimar until Saxe-Weimar's division arrived. He made the soldierly decision to march at once with his 15,000 available troops to assist Hohenlohe. Unfortunately, by the time his corps arrived, the battle was lost.