During Napoleon’s invasion of Saxony and Prussia in October 1806, both the Grande Armee and the Prussian Army were moving north on opposite banks of the Saale river. On 13 October 1806, Lannes V Corps came into contact with Prussian troops at Jena. Napoleon correctly concluded that the Prussian Army under King Frederick Wilhelm III and the Duke of Brunswick was to the west of the Saale River and ordered his corps to cross the Saale. Napoleon wished to bring the Prussian Army to battle on the Landgreffenburg, the plateau west of the Jena. Most of the Grande Armee crossed the river at Jena, but two of Napoleon’s corps, Davout’s III and Bernadotte’s I Corps, were to cross downstream at Koessen. From there, they were to surprise and strike the Prussian Army from the north.

Boldy falling upon the flank of Napoleon’s adversaries in battle after a long forced march was a task in which Davout was not a stranger. He executed the exact same mission with aplomb the previous year and assured the destruction of the Austrian and Russian armies at Austerlitz. If there was anyone in the Grande Armee that Napoleon could trust with such a difficult mission, it was Davout.

Louis-Nicholas Davout was born of minor French nobility from Burgundy. Despite his noble heritage, he survived the French Revolution when most of his peers were sent to the guillotine. A trained cavalryman, he thrived in the ranks of the French Revolutionary Army through unimpeachable integrity, uncompromising discipline, unmatched military skill, and frankly just being a bit ‘arder than his contemporaries. Davout didn’t look the part: he was prematurely balding and disdained the foppery of French officers. Davout had no time for anything that didn’t directly affect military efficacy. Napoleon, like most French senior officers, despised him at first meeting, mistaking Davout’s self-confident competence for arrogance, aloofness for pride, and utilitarian uniform for shabbiness. However, Napoleon quickly recognized that Davout was not one for the salon, but for the battlefield. When the Revolutionary government forced Davout out of the army due to his noble family, Napoleon overrode them and promoted him to general of division. He arranged Davout’s marriage to his sister in law, just to get him into the family. For these acts, Napoleon gained Davout’s undying loyalty. When Napoleon became emperor in 1804, Davout was one the few generals raised to Marshal of the Empire despite being the younger (34) than his contemporaries and one of the least experienced. He was one of the few Napoleonic commanders who saw the difference between “looting” and “foraging”, punished the former with death, correctly surmising that looting just slowed the columns down. For his tough and exacting training standards, moral incorruptibility, and unrelenting discipline, Davout quickly became known as the “Iron Marshal”.

Napoleon’s confidence in Davout was not misplaced though it would be tested during the invasion of Prussia. Davout was already passed Jena and was 15 km to the north when Lannes made contact there with the Prussian Army. The Grande Armee’s turn west put Davout’s III Corps on the far right but in a position to turn the Duke of Brunswick’s flank, if possible. To do so, III Corps would have to march north to cross the Saale at Koessen then turn south and take the Prussians from the flank and rear. Davout’s men would have to march all night to complete the 50 kms route. Come dawn on 14 October 1806, II Corps was making good time on the road from Koessen toward Auerstadt and Apolda to decisively affect the Battle of Jena.
However, Davout would never make it there. He and his 27.000 strong corps were marching southwest on the same road that the 70,000 strong Prussian main army was marching on northeast towards Leipzig. In the same dense fog that affected every movement at the Battle of Jena, neither side was aware of the other, but a clash was inevitable.

At the village of Hassenhausen, Davout sent his aide-de-camp Colonel Jean-Raymond-Charles Bourke with a detachment of light cavalry to assess the road ahead. They spotted Brunswick’s advanced guard, General-Lieutenant Gerhard von Blucher’s division of cavalry with the King of Prussia Frederick Wilhelm III at its head as if he were a Roman Consul riding in a triumph. About the same time, Prussian cavalry, considered at the time the best in the world, spotted Davout’s 3rd Division, under Gen Charles Gudin advancing on Hassenhausen. Blucher convinced Brunswick that he should immediately attack. The fog would allow his cavalry squadrons to surprise the French and defeat them before they could form squares. Blucher advanced with ten squadrons and brushed aside the Gudin’s screening light cavalry
Unfortunately for the Prussians, Bourke’s reconnaissance and Gudin’s retreating cavalry gave just enough warning for the veteran French infantry to form squares. In less than a minute, Gudin’s exposed columns were a patchwork of immobile bayonet tipped squares, and a minute after that surrounded by Prussian cavalry. A horse, no matter how well trained, won’t charge a wall of bayonets. The Prussians were reduced to riding past firing their pistols or attempting to slash their way through with sabers, all the while receiving volleys from the back ranks and canister from the guns at the corners. One square was broken up by dismounted dragoons and horse artillery but most of its inhabitants managed to withdraw to another square. The sole Prussian success of the engagement was the exception that proved the rule that mounted cavalry couldn’t break an established infantry square. Every time the cavalry reformed amidst the squares, they were hammered by French volleys. Blucher’s cavalry was forced to fall back. The massive casualties among the Prussian cavalry neutralized them for the rest of the battle.

The defeat of the feared Prussian cavalry skyrocketed the morale up and down Davout columns.

Brunswick orders his infantry forward to engage the French and closed with Gudin’s men. However, Gudin was in a strong position. His men occupied Hassesnhausen and turned it into a stronghold with defensive lines to the north of the village. More Prussian troops followed behind, but since Brunswick rode up and down the Prussian line inspiring his men, their officers couldn’t find him in the confusion of the battle. So they stopped and waited for instructions as to where to place their men in the line. Brunswick was forced to place them himself while the French filled in the line as needed. Furthermore, Gudin’s men in Hassenhausen had a better line of sight over the battlefield and could observe Prussian movement. The Prussians could not do the same.

Anchored on Hassenhausen, Gudin took on all comers but, even disorganized, the Prussian numbers began to be felt. Gudin had no troops to the south of the town and the Prussians were slowly enveloping the French left. Davout’s 2nd Division, under Gen Louis Friant formed his men to the right of Gudin and caused a panic among the Prussians as Brunswick was pushing the French left. However, the sight of French troops to the north of Gudin and French cavalry even further northwest, threatened his own left flank. Brunswick sent his highly capable chief of staff, Gehard von Scharnhorst, to sort out the north while he continued to individually place regiments in the south. Though the Prussians vastly outnumbered the French, Davout’s commanders were simply quicker to get into the line. Two thirds of Davout’s corps were fighting the Prussians while barely one third of Brunswick’s army was in the fight.

At 9:30 am, disaster struck the Prussians. The Duke of Brunswick was shot in the head and taken from the battlefield. The king took personal command. There was a reason Brunswick was in tactical and operational control of the army, King Frederick Wilhelm III was not an able military mind. He knew his limits, but with Brunswick mortally wounded he felt honor bound to take command. With Scharnhorst out of contact to the north, and the Brunswick’s subordinate commanders unwilling to step up and assist the king, paralysis wracked the Prussian Army.

Brunswick’s last commands were carried out and a massive Prussian force attempted to bypass the town to the south, but it was spotted from Hassenhausen and Davout diverted troops to block it. Nonetheless, by 11 am Davout’s two divisions were hard pressed. Morand’s division was still enroute and Bernadotte’s corps was nowhere to be seen. Because of his control of the commanding views from Hassenhausen, Davout knew he was facing the Prussian main army and accurate numbers of what he faced. He sent a report to Napoleon at Jena, who curtly told the Colonel Falcon, Davout’s aide and messenger, that “Your marshal is seeing double!”

The arrival of Morand’s 1st Division to the south of Hassenhausen around noon provided much needed relief for the Gudin in the town, then fighting on three sides.. The Prussians on the right were expecting to be reinforced from the Prussian reserve, 15,000 men under Count von Kalkreuth. However, one of Friant’s brigades along with Davout’s corps cavalry turned the Prussian right and seized the town of Poppeln, far behind the Prussian lines. In an army with outstanding division commanders, Davout trained his hardest, and Friant was by far his best. The Prussian line bent dangerously backwards under Friant’s relentless assault. Kalkreuth, with two fresh divisions at Auerstadt, but without orders, recognized the danger and decided to retake Poppeln instead of reinforcing the line. With the Prussian reserves occupied elsewhere, the sight of the fresh French troops of Morand’s division broke the Prussians opposite Hassesnhausen who had been fighting for nearly four straight hours without reprieve. Like Napoleon, the Prussian king thought he faced his adversary’s main army, so he ordered a withdrawal to reorganize his own army, identify a new commander, and fight at a better location.

Davout sensed the Prussian weakness and ordered all of his units to immediately attack. What began as a small trickle of Prussian troops fleeing to the rear became a flood. Any semblance of Prussian order dissolved in the narrow streets of Auerstadt. The Prussian retreat tuned into a rout as the king’s army encountered the remains of Hohelohe’s army fleeing west and north after being defeated by Napoleon at Jena. Only French exhaustion prevented Davout’s men from pursuing the Prussians. Not that it really mattered, even Prussian formations who had no contact with the French broke and fled for their lives.
That Davout did not show up to the Battle of Jena was one of the final indicators that Napoleon was not fighting Prussia’s main army. Bernadotte made the same mistake and instead of supporting Davout, turned around and headed toward Jena, missing both battles. It was rumored that Bernadotte deliberately chose not to support Davout who was clearly Napoleon’s favorite after the Battle of Austerlitz. A defeat for Davout at Austerlitz would have brought him down a notch and not affect Napoleon at Jena since Bernadotte could block any Prussian advance south. Whatever the case, Davout won a great victory against the odds, while Bernadotte got an ass chewing that many believe began his road to betrayal.

Davout didn’t need Bernadotte, but his casualties would have been lighter had the future King of Sweden followed and supported. Davout’s III Corps endured 7500 casualties, about one quarter of his corps, but he defeated over 70,000 Prussians, almost twice what Napoleon faced at Jena. Napoleon, ever the narcissist, attempted to downplay Davout’s victory at Auerstadt in favor of his at Jena in official dispatches back to Paris. But Davout’s victory was so overwhelming and against such great odds that even Napoleon couldn’t deny it. He awarded Davout the title of “Duke of Auerstadt”. When the Grande Armee triumphantly marched into Berlin ten days later, it was Davout’s III Corps that marched in the van.

It was said later that “Napoleon won a victory that he could not lose and Davout won a victory that he could not win.” The quote overly simplified a series of complicated engagements. The Battle of Jena was far closer than it seemed with the fog limiting Napoleon’s understanding of the battle. It was Napoleon’s corps system and his subordinates’ proclivity to concentrate and march to the sound of the guns and the Prussian hesitation to do the same that won Jena. The Battle of Auerstadt was far closer than the numbers suggest. Whereas Davout and superstar subordinates efficiently and effectively got the most out their men, Prussian disorganization and paralysis negated their superior numbers.

The French pursued the surviving elements of the Prussian Army across the country, isolating them and never giving them a chance to reorganize. Hohenlohe surrendered after the Berlin fell, Ney captured Magdeburg after a short siege of its garrison reinforced with Jena/Auerstadt refugees, and Blucher was pushed out of Lubeck in a last desperate stand by the remains of the Prussian Army. The Battle of Lubeck was a taste of what the Prussian Army was capable of in competent hands.

The French victories at the battles of Jena and Auerstadt thoroughly humiliated the Prussians and laid to rest once and for all who was the true heir of Frederick the Great. The defeats shattered the idea of Prussian invincibility and directly led to a series of reforms and retirement of the elder Prussian officers. The mass exodus of Prussian officers that came of age in the mid-18th century gave way to a new generation of dynamic reformers. Led by Scharnhorst and Blucher, and consisting of great military minds such as Neidhardt von Gneisenau and Carl von Clausewitz, among many others, the reformers identified the reasons for the Prussian losses and French victories. They remade the Prussian Army into one that defeated Napoleon in the battles from 1813 to 1815. Their contributions to military theory are still felt today.