Battle of Jena–Auerstedt

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, more specifically in today's Thuringia, between the forces of Napoleon I of France and Frederick William III of Prussia, at the outset of the War of the Fourth Coalition during the Napoleonic Wars. The disastrous defeats suffered in these battles by the Prussian Army, which had not been reformed for about half a century, subjugated the Kingdom of Prussia to the French Empire until the Sixth Coalition was formed in 1813.

The Prussians did not forget the military glory of Frederick the Great and venerated it, but by the time of the war, changes were needed for victory, despite the fact that Prussia showed itself well in the French Revolutionary Wars. Thus at Jena and Auerstedt the backwardness of the Prussian Army became apparent. By 1806, Prussian military doctrines have been unchanged for more than 50 years—tactics were monotonous, and the wagon system was obsolete. The Prussian musket of 1806 (the 1754 model) was called "the worst in Europe" by one authority; there were many recruited non-Prussians in the royal army. At the same time, Napoleon's army was recently reorganized according to the advanced corps system, which the French Emperor improved greatly by 1805, who also had such tactics as la maraude at hand. At Jena the French were led by Napoleon himself, and at Auerstedt they were led by one of the most outstanding commanders of the Napoleonic Wars, Louis-Nicolas Davout.

The battle of Jena took the Prussian supreme commander there, Prince of Hohenlohe-Ingelfingen, by surprise due to his misorientation and ignorance of the enemy. Due to this incompetence, the Prussians fought a series of isolated, disjointed engagements, unconnected by a unified plan. From beginning to end, Hohenlohe remained disoriented regarding the enemy's strength and direction of advance, and not only did not find time to maintain control of the battle but was unable to even organize an adequate retreat; whilst Napoleon showed firm will at Jena, skillfully taking advantage of both the weather conditions (fog) and the rugged terrain (see Advantage of terrain) when his troops gradually entered the battle from the march.

At Auerstedt, Davout, at the first sign of the enemy's appearance, rapidly analysed the area, took an advantageous defensive position, and quickly brought up and deployed all his forces on the battlefield. Thus, Duke of Brunswick (overall commander-in-chief) failed to take advantage of his numerical superiority. Davout showed his steadfastness and personally rode around his position during the battle whilst proving himself a good tactician. As was stated by author Nikolai Orlov, "Davout, having concentrated all his troops, correctly assessed the Prussian position and was convinced that a bold offensive would completely disrupt them. He concentrated all his efforts on their key strategic position, Mount Eckartsberg (on their left flank), and captured it. It was the main line of operations, as it provided the road to the important points of Freyburg and Berlin. Simultaneously, he used one division to take Mount Sonnenberg (on the right), which was of merely tactical interest, and was occupied by only a battalion. Having captured these two mountains, he began an artillery bombardment of the Prussians from these mountains, which turned the simple withdrawal into a rout. The French, exhausted, hardly pursed, and stopped near Auerstedt." Davout also took advantage of the confusion among the Prussian command caused by the death of Brunswick and Friedrich Wilhelm von Schmettau (divisional commander).

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.