On October 14, 1806, two battles were fought a few kilometres apart in central Germany. At Jena, Napoleon commanded about 90,000 men against a Prussian and Saxon force under Prince Hohenlohe, and at Auerstedt, Marshal Davout, with about 26,000, met the main Prussian army led by the Duke of Brunswick. Both ended in French victories.
The Prussian army had a reputation that dated from the middle of the previous century, built on harsh discipline, close-order drill, and a dependence on the bayonet charge, and it had not been tested against an army of the new kind. The officers were mostly drawn from the nobility, promotion was by seniority, and the supply system was run from magazines rather than from the country.
The French fought differently. Their units worked in skirmish order as well as in columns, their officers could act without waiting for orders, and they lived off the land. At Jena the Prussian line was pushed back and broke, and at Auerstedt Davout held against repeated attacks before going over to the offensive. The Duke of Brunswick was killed in the fighting.
The consequences came fast. Prussian resistance collapsed, and Napoleon entered Berlin on October 27. The peace of Tilsit in July 1807 cut Prussia's territory and its population by about half, and the state began a programme of reform that included the abolition of serfdom and the reorganisation of the army and the schools. The defeat is taken in German history as the starting point of the reform era.