The War of the Fourth Coalition (1806-1807) saw Napoleon defeat Prussia at Jena and Auerstädt in 1806, and Russia at Friedland in 1807, and the resulting Peace of Tilsit marked the high point of Napoleon's power. The campaign against Prussia saw Napoleon's quickest victory, with only six days elapsing between the start of the French advance on 8 October 1806 and the decisive battles of the war on 14 October. The Russians would prove to be a tougher opponent and it would take two separate campaigns to defeat them.
In 1805 Napoleon had been faced by the Third Coalition, which was based on Austria, Russia and Britain. The Prussians stayed out of this war, although by November 1805 they had decided to join the Allies. At this point Napoleon appeared to be isolated at Vienna, and facing imminent defeat at the hands of a larger Austro-Russian Army. All of this changed on 2 December 1805 when Napoleon won perhaps his most impressive victory at Austerlitz. The Austrians were forced out of the war and the Russians had to retreat back into Poland.
One month before this victory the Prussians had agreed to join the Third Coalition (Treaty of Potsdam, 3 November 1805), if Napoleon didn't agree to peace terms. A Prussian envoy, Christian de Haugwitz, arrived at Napoleon's headquarters just before the battle. He carried a virtual ultimatum from Frederick William III of Prussia, but had no chance to issue his demands before the battle of Austerlitz. Instead he had to congratulate Napoleon and wait for the French demands. The Prussians were forced to agree to surrender Cleves, Ansbach and Neuchâtel in return for Hanover, and had to join an alliance against Britain. The treaty was agreed by Haugwitz on 15 December 1805 but not ratified by Berlin until 24 February 1806.
At the start of 1806 Napoleon seemed to be in a very strong position. Austria was out of the war, Prussia had been cowed and peace negotiations were underway with Russia. Within a few months the position had changed. The negotiations with Russia eventually failed, while a series of policies served to anger the Prussians. In June the Holy Roman Empire was dissolved. The formation of the Confederation of the Rhine in July threatened Prussian influence within Germany. Napoleon's fatal blunder was to offer Hanover back to Britain as part of a wider peace deal. Prussia would have been offered other territory in compensation, but this offer weakened the peace party in Prussia and increased the influence of the war party.
This party included Queen Louise, described by Napoleon as 'the only man in Prussia' and General Hohenlohe. The king was a key member of the peace party, but by early August his limited willpower had been worn down and on 7 August 1806 the Prussians decided to go to war.
The Prussian decision was kept secret, and Napoleon didn't discover that they were mobilising their army until September. His own army was still deployed in southern Germany, in the aftermath of the War of the Third Coalition. Napoleon thus had some 160,000 men stretched out from the Rhine to the Danube and along the River Main, mainly in friendly Bavaria. The army's HQ was at Munich. The Grande Armée was probably at its peak in 1805-6. Most of the soldiers were veterans of the Ulm and Austerlitz campaigns, their leaders were of the highest quality and the army was very well organised.
The Prussian field army was of a similar size, with 171,000 men available. Morale in the army was very high, mainly because of the legacy of Frederick the Great, but the army's technical ability was much worse. The high command was a particular weakness, and really needed a strong monarch to make it work. With a weak monarch such as Frederick William III the senior commanders bickered about precedent and argued endlessly about what to do.
The Prussian army had a mixed command. King Frederick William was the commander-in-chief, and he accompanied the army but he didn’t lead it. He was accompanied by the elderly Field Marshal Richard Mollendorf, who served as his advisor but had no official post. The official commander of the army was Karl Wilhelm Ferdinand, Duke of Brunswick. Second to him was Prince Hohenlohe, who often acted in a semi-independent role during the campaign. For most of the campaign both Brunswick and Hohenlohe commanded 70,000 men.
This mixed command would almost cripple the Prussian army throughout the war. This started before the fighting began, when the Prussian high command attempted to come up with a strategy for the upcoming war. The basis of all of their discussions was the peculiar belief that Napoleon would remain on the defensive, allowing the Prussians to decide where and when to attack.
The Prussians started in September with an invasion of Saxony. The Saxon army was forced to join with them, giving them another 20,000 men (most of whom served under Hohenlohe). This move alerted Napoleon to the upcoming war, and gave the Prussians some very unwilling allies.
The Duke of Brunswick wanted to advance south-west towards Erfurt and Würzburg, through Saxony towards Stuttgart. His aim was to catch the French before they could concentrate, or if that failed to threaten their lines of communications back towards France.
Hohenlohe wanted to make a similar advance, but further east, towards Hof and Bamberg. This plan had less to recommend it, as it would have involved an advance towards the right flank of the French position and wouldn't have threatened their lines of communication. For Hohenlohe its main merit was that it would have involved his own army.
A third plan was proposed by Massenbach, one of three Prussian chiefs of staff. He suggested a formal advance from Hof south towards the Danube and then back to Saxony. The purpose of this manoeuvre is at best unclear.
Perhaps the most sensible plan was suggested by Scharnhorst, then serving as Blücher's chief of staff. He wanted to retreat east towards the Russians, fighting a series of delaying actions as they went. The combined Prussian and Russian armies would then turn on the French.
Scharnhorst's plan was dismissed as being too defensive. Massenbach's suggestion was also quickly eliminated. The choice was thus between Brunswick's advance to the south-west or Hohenlohe's advance south. After a series of inconclusive councils of war that took place in September, the king finally made a decision of sorts. Unfortunately this was to combine features of both plans, so there would be an advance south-west and an advance to the south.
Work began on the complex task of issuing detailed written orders to every unit in the army, but on 27 September this first plan was abandoned and Brunswick's plan was adopted instead. A whole new set of written orders were required.
This second plan only lasted until early October when it became clear that Napoleon wasn't staying on the defensive. The army was already moving towards Erfurt, but new councils of war were held. On 5 October a scout was sent out, and on 8 October he returned to the council and reported that Napoleon appeared to be advancing towards Bayreuth and Coburg, the first stages of an invasion of Saxony from the south. This would put him on the left flank of the Prussians, and potentially leave the road to Berlin unguarded. Yet another plan was needed.
Brunswick decided to concentrate his army west of the River Saale and try and attack the French in their flank. His main army was concentrated at Erfurt as planned on 9 October and then advanced south-east towards Blankenhain. Hohenlohe was to take up a position at Rudolstadt, on the left bank of the Saale and ten miles to the south of Blankenhain. A small reconnaissance force was to be left much further to the south-east at Hof. Hohenlohe largely ignored Brunswick's intent, and moved Prince Louis Ferdinand to Saalfeld, south of Rudolstadt and Tauenheim's Saxon divisions south-east to Auma and Schleiz. The Prussians were thus less well concentrated than Brunswick had intended, and Hohenlohe's scattered detachments were directly in the path of the advancing French.
Napoleon also considered several plans, but as the undisputed commander-in-chief of his armies he was able to come to a firm conclusion and stick to his plans. His aim was to defeat the Prussians before the Russians could join them. He thus needed a line of advance that he could use quickly and that would make it harder for the Prussians to retreat safely. His biggest problem in deciding what to do was that he couldn't understand the Prussian actions. He was assuming that they would be expecting him to go onto the offensive, as he always did, and so couldn't understand why the Prussians were willing to put their main army into such an isolated position in the west. His biggest worry was that they had entered into a secret agreement with the Austrians, and that the recently defeated Austrian army would attack the French once most of the Grand Armée was engaged in Prussia, or an agreement with the British who could land an army on the northern coast of Europe. The alternative was that the Prussians were being incredibly foolish, and in the end Napoleon had to act on this later belief and make sure that he defeated the Prussians before anyone else could intervene.
The first line of advance was east from Wesel on the Rhine. This would involve the longest movement for the French armies, and would offer few chances to prevent a Prussia retreat and so could easily be dismissed. Next was a concentration at Frankfurt and an advance north-east through the Fulda Gap. This gave a clear route into Prussia, but once again there would be a delay as the army moved west from its camps in Austria and the army would have to cross a series of major rivers. Once again the Prussians would easily be able to retreat east towards their allies.
The third plan was the one that Napoleon adopted. This was for a concentration at Bamberg, towards the centre of the current French position. The unified army would then advance north/ north-east into Saxony, potentially outflanking the Prussians. The French would then advance towards Leipzig and then Berlin, on a line that would put them between the Prussians and the Russians. Napoleon had decided in favour of this plan by mid-September when he informed Berthier that the line of operations would probably run along the River Main towards Würzburg.
The only problem with this plan was that the French had to get across the wooded hills of the Thüringerwald, which could only be crossed by three passes. Napoleon decided to split his army into three powerful columns, which would advance in parallel across the hills. This formation became known as the 'battailon carré', a giant battalion square. He believed that the Prussians would only be able to defend two of the three passes at most. If they did then the third column would attack the Prussians from the flanks or rear. If only one pass was blocked then the other two columns would converge on the blocking force. If the Prussians attempted to block all three passes with smaller forces then each column would be able to fight its way through. On this occasion Napoleon had rather over-estimated the Prussians, who left all three passes unguarded.
The French advance began on 8 October. Murat's light cavalry went ahead of each column, scouting for the Prussians. The eastern (right) column was headed by Soult's IV Corps. Ney's VI Corps was next and 10,000 Bavarians followed behind, for a total of 50,000 men.
The central column was headed by Bernadotte's I Corps, with Davout's III Corps next and the reserve cavalry and most of the Guard at the rear, a total of 70,000 men.
The western (left) column was led by Lannes' Vth Corps, with Augereau's VII behind, a total of 40,000 men. While the three columns were in the hills there was little or no contact between them. Each of the columns was expected to defeat any force of 30,000 men or less, and if they ran into larger Prussian forces then the other columns would emerge from the hills and come to their support.
By the end of 8 October the heads of the three columns had reached Coburg (left), Lobenstein (centre) and Münchberg (right). The only Prussians to be encountered were small cavalry outposts.
The first significant combat came on 9 October when the central column ran into Tauenzein's isolated command at Schleiz. The resulting battle of Schleiz was an easy French victory, and Tauenzein was forced to retreat. By the end of the day the left column was approaching Saalfeld, the centre was moving past Schleiz and the right was close to Hof.
The Prussians were now aware that the French had outflanked them and were crossing the Thüringerwald. Tauenzein was retreating, while Prince Louis at Saalfeld reported that there were French camp fires to his south. Hohenhole decided to prepare to cross the Saale to support Tauenzein. Prince Louis received orders that he read as meaning it was his role to hold Saalfeld for as long as possible while the army took up a new position behind him.
At 10am on 10 October Prince Louis was attacked (battle of Saalfeld). About an hour later he received orders to retreat to Rudolstadt, but by then it was too late - the fighting was already too fierce. The battle lasted for another couple of hours, but the French then began to get the upper hand. Prince Louis led a cavalry charge in person and was killed. After that Prussian morale collapsed and the survivors fled from the scene.
In the aftermath of this fighting the Prussians decided to retire. Hohenlohe pulled back to Jena, where on 12 October his Saxon troops suffered a brief panic. Brunswick and the king abandoned their advance to Erfurt and instead concentrated further east at Weimar. By the end of 10 October Napoleon believed that the Prussians were planning to move east, cross the Saale and take up a position at Gera on the River Elster, where they could block his route to Leipzig. He ordered his corps to move north towards Gera, hoping to block the Prussians route. If Hohenhole's plan of 9 October had been put into effective, then Napoleon's move would have been successful.
On 11 October it became clear that there were no Prussians around Gera, and that their main army must still be somewhere to the west or north-west. Napoleon still had very little accurate information to go on, and on 11 October he decided that the Prussians would probably concentrate around Erfurt.
On 12 October Napoleon ordered Murat with the cavalry to probe towards Leipzig. The rest of the army was to wheel to the left to face west ready for an advance towards the Prussians. Bernadotte and Davoût from the central column would now form the right wing of the army, with Davoût at the far right of the line heading for Naumberg and Bernadotte to his left heading for Kosen, both places with bridges over the Saale. Lannes and Augereau, from the left column, were to form the centre and head for the bridges at Jena and Kahla. The right hand column was split. Soult was ordered to move to Gera on the Elster, east of the main army, to watch for any possible Prussian move in that direction. Ney was posted a little further west, at Mittel-Pöllnitz, with orders to move further west to support Lannes if needed. At this point Napoleon expected to cross the Saale on the 14th and fight a battle around Erfurt on the 16th.
Napoleon's first orders for 13 October were for Bernadotte to join Davoût and Ney to move towards Lannes. Early that morning he received a series of reports that convinced him that the Prussians were now planning to retreat north towards Magdeburg instead of north-east to Leipzig. Napoleon altered his orders in response to this possible move. Davoût was still at Naumberg on the right. Bernadotte and Murat's cavalry were ordered to move to Dornburg, further south on the Saale. This would fill a gap that was opening up between Lannes and Davoût. Soult was ordered to send one division to Jena while the rest of his corps moved north-west to guard against a move on Leipzig. Augereau was ordered to Jena, Ney to Roda (just to the south-east) while Napoleon moved to join Lannes at Jena.
As Napoleon moved towards Jena he met a messenger from Lannes reporting that he had found 10,000-15,000 Prussians north of Jena and believed that another 20,000-25,000 more were to the west between Jena and Weimar. Napoleon now believed that he had found the main body of the Prussian army and that the Prussians were probably intending to attack Lannes. He sent out a third set of orders. Murat was still to head for Dornburg, as was Bernadotte. At this stage Bernadotte was ordered to support Lannes if he heard the sound of heavy fighting. Soult and Ney were ordered to bring their entire corps to Jena. Davout was to advance west from Naumburg and attack the Prussians at Jena from the north.
While these orders were being issued Lannes was occupying the town of Jena. He then moved onto the Landgrafenberg, a steep hill that loomed above the town. The first clashes with the Prussians came as Tauenzein's advance guard was forced off the hills and back into the nearby villages. Lannes decided to try and keep possession of the high ground even though he believed he was badly outnumbered. Napoleon arrived soon afterwards and agreed with this decision. He ordered the rest of Lannes corps to move onto the heights, supported by the Imperial Guard. The move was made after dark to hide it from the Prussians. Most impressive was the effort taken to move some heavy artillery onto the hilltop, a move that required the French to improve the quality of the single track that led up the hill, all in a single night. Overnight the French moved guns and reinforcements on the Landgrafenberg, ready to fight a major battle on the following day.
Napoleon expected to fight a major battle on 14 October, but not the battle that actually took place. He believed that he was facing the main part of the Prussian army just to the north of Jena. Davoût and Bernadotte's role was to head north then west to take up a blocking position behind the Prussians, to make sure none of them escaped from the trap.
In fact the main body of the Prussian army was already further north than Napoleon believed. He was about to attack Hohenhole's flank guard (battle of Jena), while Davoût's single corps ran into the main Prussian force under the Duke of Brunswick (battle of Auerstädt). Bernadotte disgraced himself by ignoring orders to cooperate with Davoût and instead spent the day marching between the two battles, taking part in neither of them.
The battle of Jena (14 October 1806) was a surprisingly hard-fought conflict, especially given that the Prussians were quite badly outnumbered. Their best chance of a significant victory was lost before the battle even began, when Napoleon and Lannes' corps were camped on the Landgrafenberg, facing a rather larger Prussian force. The battle began soon after 6am when Lannes attacked in the centre, with Augereau and Soult coming into action a little later. After some hard fighting the French pushed the Prussians back towards Vierzehnheiligen, creating the space for the rest of the army to deploy. On the French right Soult ran into Holtzendorff, moving south towards the sound of the guns. This second phase of the battle also ended with a French victory and Holtzendorff retired, leaving Soult free to join the main fight. The third stage of the battle was triggered by Ney, who plunged straight into the fighting, advanced well ahead of the French line and had to be rescued. Ney's charge left a gap in the French line, which the Prussians attempted to exploit, but at a key moment they paused to wait for reinforcements. The French were able to make contact with Ney and close the gap in their line. Finally, in the early afternoon Napoleon launched a general attack that broke the Prussian lines and forced them into a costly retreat. The Prussians and Saxons had lost 10,000-11,000 dead or wounded and 15,000 prisoners, nearly two thirds of the original army. Rüchel's detached force arrived after the main battle was over, and briefly clashed with the pursing French, before being forced to flee from the field itself.
Further north a second battle was being fought. Marshal Davoût's single corps had run into the main part of the retreating Prussian army. Advancing west from Naumburg Davoût crossed the Saale at Kösen and ran into the advancing Prussians. The outnumbered French were hard-pressed in a battle largely fought around the village of Hassenhausen (although the battle became known as the battle of Auerstädt), but the Prussians were never able to bring their entire army into the fight and the Duke of Brunswick was mortally wounded quite early in the fight, leaving the King of Prussia in ineffective command of the army. The Prussians were eventually forced to retreat after Davoût launched an effective attack. At first the Prussians managed to retreat in good order, but they then ran into the defeated remnants of Hohenlohe's army retreating from Jena and the army began to fall apart.
Napoleon didn't realise that this second battle was being fought until it was over. When he returned to his camp Napoleon was met by one of Davoût's staff officers, who reported the outcome of the battle. At first Napoleon refused to believe that he had misjudged so badly, and told the messenger that 'Your marshal must be seeing double'. It soon became clear that Davoût had indeed fought the larger battle, and in the following day Napoleon paid tribute to his subordinate in the Fifth Bulletin of the Grande Armée - 'On our right, Marshal Davoût's corps performed wonders. Not only did he contain, but he pushed back, and defeated, for more tha three leagues, the bulk of the enemy's troops, who were to debouch through Kösen'. Davoût was also given the honour of leading the grand entry into Berlin.
In the immediate aftermath of the battle the French pursuit was quite limited. Murat reached Weimar in the west and Bernadotte was at Apolda, to the north, but he arrived too late to stop the fleeing Prussians from escaping to the north and north-west. Napoleon's plan for the pursuit was to have part of his army directly press the Prussians as they retreated north, while a second part of the army moved along a line a little further to the east, passing through Halle and Dessau. Murat, Soult and Ney carried out the first task while Bernadotte's fresh corps began the flank march. Augereau, Lannes and Davout were to join him after a few days of rest.
On 16 October Murat was at Erfurt, where he captured 9,000-14,000 prisoners. On 17 October Bernadotte helped restore some of his reputation, when he defeated the Duke of Würtenberg with the Prussian reserve force at Halle. In this battle the Prussians lost 5,000 of their 13,000 men. By the following day the resting corps had joined the chase and by the 20th the French had reached the Elbe. On the same day Frederick William left the army and headed east towards the River Oder and relative safety with the Russians. Hohenhole was left in command of what was left of the army. The Prussian army now split into two main forces. Blücher was in the west, heading towards Brunswick, with Lubeck on the Baltic as his eventual destination. The main army under Hohenhole attempted to move north-east to Stettin on the River Oder, where he hoped to join the Russians.
On 21 October the French began to cross the Elbe. The Prussians attempted to destroy a bridge over the river at Wittenberg but the locals prevented them from doing this and Davout was able to get his entire corps over the river. To his left Marshal Lannes managed to repair a burnt bridge and had the cavalry and the first of his infantry over by the end of the day. Thirty miles to the west of Davout Bernadotte managed to find enough boats to cross the river at Bardy and was over by the morning of 22 October. On the same day Ney, Soult and Murat were close to Magdeburg. Ney was given the task of besieging Magdeburg, which surrendered on 11 November.
The main army now focused on Berlin. By 24 October the French reached Potsdam, and on the following day Napoleon visited the tomb of Frederick the Great, one of the few commanders he admitted to admiring. After his visit he looted the church, taking Frederick's sword, general's sash, Ribbon of the Black Eagle and the standard of the Prussian Guards. The French made their formal entry into Berlin on 27 October, with Davout's corps at the head of the army in recognition of his achievements at Auerstädt. A few days later Augereau arrived with the Prussian prisoners of war, and in an attempt to increase the humiliation of the Prussian army he forced them to march through the city and past the French embassy. The humiliation of the arrogant young noblemen of the Prussian Chevalier Guard was apparently quite popular in Berlin.
After the occupation of Berlin the French armies began to split, with some heading for the Oder to guard against any Russian intervention while the rest headed west to deal with the remains of the Prussian army. Jerome's IX Corps joined the advance, moving from Dresden up to Frankfurt-on-Oder. Murat and Lannes made for Stettin. On 26 October the Prussian flank guard was defeated at Zendenick, and on 28 October Hohenhole surrendered the remains of his army to Murat's cavalry at Prenzlau.
The only remaining intact Prussian army was the small force commanded by the Duke of Weimar and Blücher. This army was heading for Lübeck, where they hoped to find Swedish reinforcements and perhaps escape by sea to Britain. This army was around 22,000 strong. It was being followed by Bernadotte with 12,000 men, with Soult a day behind. Blücher reached Lübeck on 5 November, but before he could make the city secure the French attacked (6 November). The city fell and was looted by the victorious French. Scharnhorst and 10,000 men surrendered. Blücher escaped, but was forced to surrender on the following day having run out of both food and ammunition. Another 8,000-10,000 men surrendered with Blücher. On the same day 600 Swedish troops were captured. Bernadotte clearly made quite an impression on the Swedes for in 1810 he was elected Crown Prince of Sweden. He ended the Napoleonic Wars fighting against his former master, survived to become King Carl XIV of Sweden and Norway and founded a dynasty that still survives.
At the end of a short campaign Napoleon had destroyed the Prussian army and occupied all of Prussia west of the Oder, but he had failed to capture Frederick William, who escaped into the German half of Poland, where he received support from the Russians, and under pressure from his wife refused to consider peace. For the first time one of Napoleon's military triumphs had failed to lead to a political triumph, and he was forced to take the war east into Poland.
Napoleon was now faced with the dangers of a campaign against Russia, which would have to be fought at a great distance from France, and with potential enemies on both flanks. On his left the danger came from Britain and to a lesser extent from Sweden, but Napoleon didn't expect the British to risk landing an army on the north-western coast of Europe, and believed that he had enough troops in France to deal with any attack that did happen. On his right the danger came from Austria, defeated in 1805 but still quite powerful. Any Austrian intervention while Napoleon was engaged in Poland could have been very dangerous. In order to deal with this threat the French army in Italy was expanded, in the expectation that this threat to their southern border would prevent them from acting in the north.
The Russians had two armies in the field at the start of the campaign, both under the overall command of the elderly Field Marshal Mikhail Fedorovich Kamenski. The first army, under General Bennigsen, was around 55,000-66,000 strong. The second, under General Buxhöwden, was made up of the Russian divisions that had been defeated at Austerlitz, and was around 36,000-37,000 strong. It arrived in the Polish theatre late in December. There was also a small Prussian army that had survived the disasters of 1806, but this only consisted of the corps of General Lestocq, and was no more than 15,000 strong.
At the start of the campaign Napoleon's army was split in two. He had 80,000 troops (Davout, Lannes, Augereau and Jerome) available for the initial advance, while a similar number of men (Bernadotte, Ney and Soult) would become available as they returned from crushing the last embers of Prussian resistance in the west.
In November 1806 Napoleon decided to take up winter quarters on the east bank of the Vistula. This would mean he wouldn't have to cross a major river at the start of the campaign of 1807, the Prussians wouldn't be able to recruit in their Polish lands and the army would be able to cover the sieges of Danzig, Stralsund and Kolberg, important fortresses on the Baltic coast. He wasn't entirely sure where the Russians were in early November, but he was confident that his troops could reach Warsaw before them.
The advance to the Vistula passed off without any problems. In the centre Davout's III Corps was to advance to Posen and then Warsaw. On the right Jerome's IX Corps (under the command of Murat) was to advance towards Kalisch and watch the Austrian border. On the left Lannes and Augereau were both to advance towards Thorn on the Vistula, Lannes from Stettin and Augereau from Berlin. On the far left Mortier's VIII Corps was to guard the North Sea coast against any possible landings. As the rest of the army arrived from the west Ney and Bernadotte would be sent towards Thorn and Soult and Bessière's cavalry towards Warsaw.
In the meantime Napoleon was carrying on peace negotiations with the Prussians, but his terms were very severe. The Prussians were to withdraw their remaining troops to the east of the Vistula. The French were to be allowed to occupy the west bank of the river around Warsaw and a series of key fortresses. Finally the Prussians would ensure that all Russian troops left their territory. King Frederick William was willing to consider even these harsh terms, but Queen Louise was not, and she was able to override her husband and by the end of November the Prussians had officially rejected Napoleon's terms.
As the French advanced they found small parties of Prussians, who they forced to retreat. Lestocq retreated into Thorn, but all he could do was watch as the French advanced past him towards Warsaw. The first contact with the Russians came on 27 November when Murat encountered some Cossacks to the west of Warsaw. On the Russian side Bennigsen had actually reached Warsaw ahead of the French but he decided not to defend the city. On 28 November the Russians retreated to Praga, on the eastern bank of the Vistula, and that evening Murat occupied Warsaw.
On 1 December the Russians began a general retreat from the Vistula. Bennigsen decided to pull back and join up with Buxhowden's army. Bennigsen withdrew to Ostrolenka, around forty miles to the north of Warsaw, while Buxhowden halted thirty miles to the east. The French followed up, and by 8 December Davout's III Corps had crossed the Vistula and was occupying the small triangle of Prussian land between the Vistula and the Bug while Lannes and V Corps held Warsaw and Praga. Thorn had fallen on 6 December, and the French line now ran largely along the Vistula. Ney's VI Corps was around Thorn. Augereau's VII Corps was just to the west of Warsaw. Only Bernadotte (I Corps) and Soult (IV Corps) were still to arrive, and they were both around Posen.
Benningsen now decided that he had retreated too far, and decided to try and hold the line of the Bug and try to retake Thorn. Both moves failed. Lestocq found Thorn too strong held to attack, while on 10 December Davout began to cross the Bug, close to his junction with the Vistula. By the morning of the 11th Davout held a strong bridgehead on the north bank of the Bug and the Russians had retreated east across the River Ukra, which flows south into the Bug three miles east of the junction of the Bug and Vistula. The Russians attempted to occupy Modlin, just to the north of the French bridgehead on 11 December, but were repulsed. After that failure the Russians decided to try and defend the line of the Ukra. Murat reported that they were retreating across the River Narew, the next tributary of the Bug east of the Ukra, and in response Napoleon issued orders for a general pursuit, but it was quickly clear that this wasn't the case. Napoleon altered his plans and prepared to force his way across the Ukra.
The new orders were issued on 15-16 December. Ney was to move east from Thorn to Gollub. Initially Bernadotte was to replace Ney at Thorn, but he was then ordered to follow Ney with two of his three divisions. Soult, who was now over the Vistula, was ordered to advance east to Plonsk. Augereau was also ordered to move to Plonsk. Davout was to move most of his men to the north bank of the Bug. Lannes was to occupy the south bank of the Bug. At the same time the Russians were moving towards the Ukra, and their line soon stretched along the river.
The French began to move on the night of 23-24 December. Napoleon visited Davout at the mount of the Ukra and ordered a night attack, which was carried out successfully (combat of Czarnowo, 23 December 1806). At the other end of the French line the Prussians attempted to retake Biezun on the Ukra, having lost the place on 19 December. The resulting combat of Biezun (23 December 1806) was a crushing French victory. The Prussians were forced to retreat to the north-east and within a few days they had been forced to retreat towards Konigsberg and away from the Russians.
After their defeat at Czarnowo the Russians decided to retreat towards Ostrolenka. Napoleon tried to cut off their lines of retreat in an attempt to win a decisive victory, but his plans misfired. On 26 December Marshal Lannes ran into Bennigsen's army at Pultusk, while Augereau and Davout ran into Gallitzen's rearguard further to the north-west at Golymin. Soult's corps moved too slowly to take part in the fighting at Golymin, while Ney was pushing the Prussians away to the north east. The battle of Pultusk saw the French outnumbered by the Russians, while the battle of Golymin reversed that. In both cases the battles were inconclusive, and the Russians were able to continue their retreat. The French briefly attempted to follow, but on 28 December Napoleon halted the pursuit and ordered his men into their winter quarters.
Napoleon expected that he would be left alone in his winter quarters, but he did plan for any Russian move against his centre or right. He would be surprised on both counts. On 2 January Buxhowden held a council of war and the Russians decided to go back onto the offensive, and to launch that offensive against the French left wing in East Prussia. At this point Buxhowden was the senior Russian commander, with Bennigsen officially serving under him, but after floating ice broke the bridge linking the two Russian armies Bennigsen broke camp and led six divisions north. This might have been something of a gamble, but in mid-January Buxhowden was recalled and Bennigsen given command of the army.
The Russians moved in a large loop that took them behind the forest of Johannesburg before they turned west to advance across West Prussia. This took them past Ney's corps and towards Bernadotte, who wasn't expected to be attacked - Napoleon believed that any Russian moves would come further south.
While Bennigsen was moving into East Prussia Ney was ignoring Napoleon's orders not to make any offensive moves and instead advanced north from his assigned area towards Konigsberg. Although Napoleon blamed Ney for the start of the Russian offensive, this was unfair, as the Russians had already drawn up their plans before Ney moved forward. Ney's move also provided Napoleon with some warning of the Russian move after the leading Russian units ran into some of Ney's men on 19 January. This gave Bernadotte enough warning to mass some of his men and his men clashed with the Russian advance guard at Mohrungen (25 January 1807).
It took several days for Napoleon to realise what was going on. As late as 26 January he believed that the Russians were planning to go into winter quarters in front of Ney. On the following day the penny finally dropped and Napoleon realised that Bennigsen was planning to defeat his left wing, cross the Vistula and potentially force the entire French army to retreat to the west. Napoleon now put in place a plan that could have led to the decisive battle he desired. The bulk of his army was ordered out of winter quarters. Davout, Augereau and Soult and Murat's cavalry were to move up the River Alle. Bernadotte was ordered to pull back south-west towards Thorn, but he never received that order and remained where he was close to the River Passarge.
Napoleon's plan might have succeeded, but on 31 January a copy of his orders was captured by the Russians, and reached Bennigsen on 1 February. He ordered a retreat, and the Russian army retreated out of the French trap. Napoleon caught up with the Russians at Jonkowo (3 February 1807) but this was an inconclusive battle. On the night of 3-4 February the Russians resumed their retreat, heading towards Preussich Eylau.
On 7 February Napoleon caught up with the Russians at Preussisches Eylau. A fierce battle broke out in the town that evening, probably caused by an accidental clash between a French baggage train and Russian troops in the town (Napoleon later claimed this fighting was deliberate). The main battle of Eylau took place on the following day. At the start of the battle the Russians had 67,000 men, the French only 45,000 men, but Ney and Davout were expected to arrive during the day. Soult was posted on the French left and Augereau on the right. Soult was soon under severe pressure and Napoleon ordered Augereau to launch an attack. This went badly wrong - in a blizzard Augereau's column wandered off course and ended up in front of a battery of seventy Russian guns. Augereau's corps suffered very heavy damaged and was forced to retreat. The Russians followed up and Napoleon was nearly captured. After his close call he ordered Murat's cavalry to charge the Russian centre. The French cavalry smashed through the Russian centre and then safely returned to French lines, attacking the Russian artillery on the way back. As daylight faded Davout's corps appeared in strength and began to push back the Russian left. Lestocq's Prussians then arrived and halted this French advance. Ney was last to arrive and made some progress before nightfall ended the battle.
Both sides suffered heavy losses at Eylau, but the French probably had the worst of the fighting and may have suffered as many as 25,000 casualties. Overnight the Russians withdrew, but Napoleon's army was too battered to pursue. The French claimed to have won a major victory, but the battle was at best a draw. The entire winter campaign had ended in disappointment for the French, who had failed in their attempts to win a decisive battle that might have ended the war. The two sides now finally went into winter quarters. The French successfully besieged Danzig, but the main armies didn’t begin to move until the summer of 1807.
The final stage of the campaign was fought between the rivers Passarge and Alle. Both rivers run north through the campaign area. The Passarge ran generally north/ north-west past Deppen, Lomitten and Spanden into the Frisches Haff or Vistula Lagoon, a coastal lagoon that runs parallel to the coast, with Konigsberg at the eastern end and the mouth of the Vistula just past the western end. Danzig is just a little further to the west.
The Alle is a little further to the east. In its upper reaches it runs north, parallel to the Passarge. It then turns north-east and flows past Heilsberg and Friedland before flowing into the westward flowing River Pregel. The Pregel flows west into Königsberg.
At the end of the winter campaign of 1806-1807 the French had taken up a position along the Passarge, with a presence on the upper Alle and a large army besieging Danzig. Marshal Ney was in the most exposed position, with his corps posted around Guttstadt on the Alle
The Russians were based further down the Alle, with their advance guard (under Prince Bagration) at Launau, where the river turned north-east to flow towards Heilsberg. There was also a Prussian force 15,000 strong on the lower Passarge.
Napoleon was unwilling to make his move until Danzig had fallen. By mid-May the fall of the city was certain, and he began to prepare for an advance on 10 June. He had thought that the Russians might have risked a battle in an attempt to save Danzig, but he didn’t expect them to make any move after the fall of the city.
He was thus caught out by surprise when Bennigsen launched a major attack on Ney's isolated corps on 5 June. The Russians planned a complex operation with no fewer than six separate columns. Some were given the task of keeping the French pinned in place on the Passarge while the rest were to envelope Ney.
Although the French were caught out, they responded quickly. Ney in particular was a master of the fighting retreat, and by the end of 6 June the Russian offensive had run out of steam. Further back Napoleon organised a full scale response to the attack, ordering most of his army onto the move. On the Russian side Bennigsen equally quickly realised that his plan had failed, and on the evening of 7 June ordered his troops to retreat. At first he hoped to fight at Guttstadt on 9 June, but after reaching that position he decided it wasn't strong enough. Instead he continued to retreat north, along the right bank of the Alle towards Heilsberg, with a rear guard on each bank of the river. On the same day Napoleon crossed the Passarge at Deppen and moved towards Guttstadt. By the time he arrived the Russians were gone, and there were only some minor skirmishes around Guttstadt.
The first major battle of the campaign came on the following day. The Russians had a strong position at Heilsberg, with defence works on both sides of the river. The battle of Heilsberg fell into three phases. The first saw the French push the Russian rearguard out of its positions on the left bank of the Alle. The second saw the main assaults on the Russian redoubts, by Soult's infantry, all of which were beaten off. The third was a last evening attack on the Russian position, carried out by the late-arriving Lannes. At the end of the day the French had been repulsed and had suffered the heavier losses, but on the following day the French threatened to outflank the Russian position and Bennigsen decided to continue his retreat down the Alle.
Napoleon continued to misjudge his opponent. His first assumption was that Bennigsen would cross to the left bank of the Alle somewhere downstream, and probably concentrate at Domnau, between the two rivers, from where he could block the French route to Königsberg. He decided to try and beat the Russians to that city, now the last major place in Prussian hands. Murat and Soult were ordered to march directly for Königsberg. Davout was to move on their right, while the main body of the army headed for Domnau. Lannes was sent towards Friedland to prevent the Russians from retreating east across the Alle.
Early on 13 June Napoleon discovered that there were no Russians at Domnau. He assumed that this meant they were sticking to the right back of the Alle after all, and would be heading north to the River Pregel, before heading west towards Königsberg. In fact Bennigsen was concentrated at Friedland, and Lannes was heading towards a potential trap. Late on the afternoon of 13 June the French and Russian advance guards fought in Friedland, and the Russians took possession of the town. Overnight Bennigsen began to move troops from the right to the left bank of the Alle, while Lannes moved most of his corps up.
The final battle of the war came at Friedland on 14 June. The Russians took up a rather vulnerable position on the left bank of the river, with the Alle at their backs and their position split in two by the steep sided valley of the Mill Beck. The battle fell into two phases. In the first the Russians had a chance to inflict a defeat on Lannes, while Lannes had the task of keeping the Russians on the west bank until Napoleon could rush reinforcements to the area. Lannes came out on top in this part of the battle, and by noon the French probably had more men on the battlefield. Bennigsen missed a chance to retreat back across the river as Napoleon prepared for his attack. The second phase of the battle began at 5.30pm when Ney's Corps attacked the Russian left. Over the course of the next few hours the Russian left was forced back into Friedland, while the right was pinned down north of the Mill Beck. The Russians suffered very heavy losses, but they were saved from a total disaster by the discovery of a ford downstream from Friedland late in the day. Even so they lost at least 20,000 men, a third of Bennigsen's force, and three times the French losses.
In the aftermath of the battle the French pressed the Russians back towards their borders. As the French reached the Niemen Tsar Alexander sent an envoy to open peace talks. The two Emperors famously met on a raft in the middle of the Nieman at Tilsit, where they formed an unexpected alliance. The resulting Treaty of Tilsit effectively saw Napoleon and the Tsar divide Europe into French and Russian spheres of influence. The Russians agreed to join the Continental System, and to recognise the new Kingdoms created by Napoleon. Napoleon abandoned his Turkish allies and agreed to give the Russians a free hand in the European provinces of the Ottoman Empire. The Russian claim to Finland was acknowledged (and the area was conquered in the Finnish War of 1808-1809). In return the Russians agreed to join the Continental System, to take part in the capture of Gibraltar and to force Denmark and Sweden to join the Continental System. British agents discovered the terms of these secret agreements, and this triggered the second British attack on Copenhagen, carried out to prevent the French from getting the Danish fleet.
Prussia was the main victim at Tilsit. She lost all of her lands west of the Elbe, the fortress of Magdeburg and their Polish provinces. The western provinces became part of the Kingdom of Westphalia, to be ruled by Napoleon's brother Jerome. The Polish lands became the Grand Duchy of Warsaw, officially ruled by the King of Saxony, but effectively ruled by Napoleon's representative.
The War of the Fourth Coalition ended with Napoleon at the height of his powers. He now dominated an area that ran from the Pyrenees to the borders of Russia and south into Italy. In the course of two years Austria and Prussia had been humbled, and Russian turned from a determined foe into an ally. For a brief period Britain stood alone, and Napoleon's position in most of Europe remained effectively unchallenged until the 1812 invasion of Russia. The one Austrian attempt to stand up to him ended after his final major victory, at Wagram in 1809. However at the other end of Europe Napoleon made a foolish attempt to take over Spain and Portugal, triggering the long Peninsular War. Napoleon's relationship with Tsar Alexander was also less secure than he originally hoped, and even by 1809 Napoleon was beginning to lose faith in the partnership.