Battle of Jena–Auerstedt

Two battles fought on the same day, 14 October 1806, a short distance apart in what is now Thuringia and Saxony-Anhalt, destroyed the army of Prussia in a single afternoon. At Jena, Napoleon himself routed a Prussian and Saxon force under Prince Hohenlohe; at Auerstedt, to the north, Marshal Louis-Nicolas Davout's lone corps beat the main Prussian army, which was more than twice its size. The twin defeats decided the War of the Fourth Coalition against Prussia and set off the reforms that would later transform the Prussian state.

Prussia still revered the victories of Frederick the Great, but by 1806 its military doctrine had barely changed in half a century. Its muskets were dated, its supply wagons cumbersome, and its command top-heavy: even the post of chief of staff was shared among three officers, and arguments over five rival war plans let the French seize the initiative. Napoleon's Grande Armée, by contrast, was organised into flexible self-contained corps and had been kept ready for war since the campaign against Austria and Russia the year before.

After Prussia declared war, Napoleon pushed about 180,000 men through the Franconian Forest towards Saxony and Berlin. Facing him were around 130,000 Prussians and 20,000 Saxons.

Fighting began in fog on the morning of 14 October on the plateau near Jena. Napoleon fed troops into the battle as they arrived, eventually massing some 96,000 men nearby, though perhaps 40,000 actually fought. Marshal Michel Ney attacked without orders and was nearly surrounded, forcing Napoleon to send Marshal Jean Lannes to his aid and to steady the weakened centre with the Imperial Guard. The Prussians failed to exploit the opening, and their idle infantry was cut down by artillery and skirmishers. Around 1 p.m. Napoleon ordered a general assault that broke both Prussian flanks. Hohenlohe's army collapsed, losing about 10,000 killed or wounded, 15,000 prisoners and 150 guns, and a relief corps under General Rüchel arriving from Weimar was swept away too. Napoleon believed he had beaten the main enemy army.

In fact, the main Prussian army of about 64,000, accompanied by King Frederick William III and commanded by the Duke of Brunswick, was further north. Davout's III Corps, marching south to join Napoleon, ran into it in the fog near the village of Hassenhausen soon after 7 a.m. Davout's divisions arrived one by one and formed squares, holding off repeated attacks by infantry and by Gebhard von Blücher's cavalry under heavy fire. Around 10 a.m. Brunswick was mortally wounded leading an assault, and another senior commander, Schmettau, was badly hurt. The Prussian command fell apart. At 11 a.m. Davout counter-attacked, and by about noon the king ordered a retreat. Davout's corps lost about 7,000 killed or wounded; Prussian casualties were about 13,000.

Marshal Jean-Baptiste Bernadotte, whose corps was within earshot, did not come to Davout's aid, keeping instead to his last written orders. The episode caused lasting bitterness between the two marshals, and historians still debate who was to blame.

Napoleon at first refused to believe Davout's report, but later made him Duke of Auerstedt and let his corps enter Berlin first, on 25 October. A relentless pursuit followed. Large Prussian forces surrendered at Erfurt, Prenzlau and elsewhere; Blücher was cornered at Lübeck and gave himself up on 7 November, and the fortress of Magdeburg fell on 11 November. The war then turned east against Russia.

The humiliation convinced reformers who had fought in the campaign, including Gerhard von Scharnhorst, August von Gneisenau and Carl von Clausewitz, that Prussia's army and society had to be modernised. Their reforms helped Prussia play a leading part in driving the French out of Germany during the later Napoleonic Wars, and the memory of defeat fed German nationalism. In Paris, a bridge that Napoleon named after the battle still bears its name.

Our 1800 map shows the Kingdom of Prussia at its height before the disaster, and the 1815 map shows it restored and enlarged after Napoleon's final defeat; the First French Empire at the height of its power falls between the two.