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, at the outset of the War of the Fourth Coalition during the Napoleonic Wars.

The defeat suffered by the Prussian Army subjugated the Kingdom of Prussia to the French Empire until the Sixth Coalition was formed in 1813.

Following the Prussian declaration of war, Napoleon initiated his campaign against the Fourth Coalition by thrusting a 180,000-strong force through the Franconian Forest.

[9] In comparison to the modern, tightly organized structure of the Grande Armée, the Prussian command was bloated and inefficient; key roles were divided between multiple officers, creating uncertainty and disagreement in the coordination of field movements.

Initially 48,000 strong, the Emperor took advantage of his carefully planned and flexible dispositions to rapidly achieve local superiority, with a force reaching 96,000 men.

Soon after it was committed to battle and Hohenlohe rode up to take personal command of the corps, they were ridden over and sent fleeing to the rear in irretrievable rout, with Ruchel being wounded.

Nevertheless, Jena was a fierce battle, with 5,000 French killed, wounded or captured;[11] and Napoleon mistakenly believed that he had faced the main body of the Prussian army.

Although outnumbered more than two to one, Davout's superbly trained and disciplined III Corps endured repeated attacks before it eventually took the offensive and put the Prussians to flight.

Though within earshot of both battles, Marshal Bernadotte controversially took no steps to come to Davout's aid, refusing to take the initiative and instead adhering to the last written set of Napoleon's orders.

Although Prussia had begun its mobilization almost a month before France, Napoleon had kept a high state of readiness after the Russian refusal to accept defeat after the War of the Third Coalition.

Napoleon had a major portion of his Grande Armée in position in present-day Baden-Württemberg in southwest Germany and thus decided on a northeast advance into Saxony and on to Berlin.

The skirmishes had little decisive success, save for a breakthrough by the French General Saint-Hilaire, who attacked and isolated the Prussian left flank.

[16] General Étienne Gudin's Division were on the move from Naumburg before 6:30 a.m. By 7 a.m. the 1st Chasseurs were stopped cold in their tracks outside of Poppel by Prussian cavalry and artillery.

By noon Schmettau's center was broken and forced back over the Lissbach Stream, Blücher's cavalry was blown, and Wartensleben was trying to reposition his troops.

[11] Napoleon initially did not believe that Davout's single Corps had defeated the Prussian main body unaided and responded to the first report by saying "Your Marshal must be seeing double!

[18] In the early hours of 14 October, Davout received a courier from Berthier in which he wrote: "If the Prince of Ponte Corvo [Bernadotte] is with you, you may both march together, but the Emperor hopes that he will be in the position which had been indicated at Dornburg."

[14] Bernadotte later cited the poorly written, equivocal nature of the verbal order, as discretionary and complied with Napoleon's wish to be at Dornburg instead of accompanying Davout.

[13] However, contemporary evidence indicates that far from scenes of recriminations and insults alleged by Davout and his aides-de-Camp against Bernadotte the night of the battles, Napoleon was unaware anything was amiss, inasmuch as I Corps had played the part assigned to it by the Emperor, until days later.

[23] On the Prussian side, Brunswick was mortally wounded at Auerstedt, and over the next few days, the remaining forces were unable to mount any serious resistance to Murat's ruthless cavalry pursuit.

Bernadotte crushed Eugene Frederick Henry, Duke of Württemberg's Prussian Reserve Army on the 17th in the Battle of Halle, partially redeeming himself in Napoleon's eyes.

21,000 Prussian field troops remained at large west of the Oder as November began under the command of Gebhard Blücher.

French advances prevented his corps from crossing the Oder, or moving toward Stettin to seek waterborne transport to East Prussia.

The Prussians then violated the neutrality of the Hanseatic City of Lübeck and fortified it with the intent of joining forces with an allied Swedish contingent there on its way home, and commandeering ships in the hopes of reaching a safe harbor.

However, Blücher and Winning's corps was surrounded and destroyed in what became the Battle of Lübeck on 6 and 7 November after Bernadotte's I Corps, still smarting from the Emperor's censure, stormed the fortified city gates, poured into the streets and squares breaking hasty attempts at resistance and captured Blücher's command post (and his Chief of Staff Gerhard von Scharnhorst) as Soult's troops blocked all escape routes.

On the morning of 7 November, with all hope of escape extinguished, Blücher surrendered personally to Bernadotte and went into captivity with 9,000 other Prussian prisoners of war.

Martin van Creveld has stated about the effects on command: Thus Napoleon at Jena had known nothing about the main action that took place on that day; had forgotten all about two of his corps; did not issue orders to a third, and possibly a fourth; was taken by surprise by the action of a fifth; and, to cap it all, had one of his principal subordinates display the kind of disobedience that would have brought a lesser mortal before a firing squad.