The Battle of Jena was a comprehensive French victory over the combined Prussian and Saxon armies on the 14th of October 1806 at Jena, Germany during the Napoleonic Wars. Prussian and Saxon losses amounted to some 40, 000 troops and 200 guns, while French casualties were 14,000. Napoleon so broke the Prussian forces that they were unable to prevent him marching on Berlin, and this disaster led to the complete overhaul and re-organisation of the Prussian Army which laid the foundations for its subsequent military prowess. Research Battle of Jena