The twin battles of Jena and Auerstedt (German pronunciation: [ˈjeːna … ˈaʊ̯ɐ.ʃtɛt]; older spelling: Auerstädt) were fought on 14 October 1806 on the plateau west of the river Saale in today's Germany, between the forces of Napoleon I of France and Frederick William III of Prussia. The decisive defeat suffered by the Prussian Army subjugated the Kingdom of Prussia to the French Empire until the Sixth Coalition was formed in 1813.Several figures who were later integral to the reformation of the Prussian Army participated at Jena–Auerstedt, including Gebhard von Blücher, Carl von Clausewitz, August Neidhardt von Gneisenau, Gerhard von Scharnhorst, and Hermann von Boyen.