Forewarned of Prussia’s intention to declare war on France, Napoleon decided to strike first with a bold advance from Wurzburg into Saxony. On 14 October the double battle was fought: Napoleon with 96,000 men and 120 guns engaged and heavily defeated Prince Hohenlohe and General Ruchel. The decisive engagement was fought further north where Marshal Davout with 27,000 men and 40 guns routed the main Prussian army under Frederick William IV and the Duke of Brunswick. This title examines these two battles, Jena and Auerstadt in detail, showing clearly the swiftness with which Napoleon dealt Prussia’s military machine a severe blow.