The Fourth Coalition (1806–1807) of Great Britain, Prussia, Russia, Saxony, and Sweden formed against France within months of the collapse of the previous coalition. Following his triumph at the Battle of Austerlitz and the subsequent demise of the Third Coalition, Napoleon looked forward to achieving a general peace in Europe, especially with his two main remaining antagonists, Britain and Russia. One point of contention was the fate of Hanover, aGerman electorate in personal union with the British monarchy that had been occupied by France since 1803. Dispute over this state would eventually become a casus belli for both Britain and Prussia against France. This issue also dragged Sweden into the war, whose forces had been deployed there as part of the effort to liberate Hanover during the war of the previous coalition. The path to war seemed inevitable after French forces ejected the Swedish troops in April 1806. Another cause was Napoleon's formation in July 1806 of the Confederation of the Rhine out of the various German states which constituted the Rhineland and other parts of western Germany. The formation of the Confederation was the final nail in the coffin of the moribund Holy Roman Empire and subsequently its last Habsburg emperor, Francis II, changed his title to simply Francis I, Emperor of Austria.

The Battle of Schleiz was fought between a Prussian-Saxon division under Bogislav Friedrich Emanuel von Tauentzien and a part of Jean-Baptiste Bernadotte's I Corps under the command of Jean-Baptiste Drouet, Comte d'Erlon. It was the first clash of the War of the Fourth Coalition. As Emperor Napoleon I of France's Grande Armée advanced north through the Frankenwald (Franconian Forest) it struck the left wing of the armies belonging to the Kingdom of Prussia and the Electorate of Saxony, which were deployed on a long front. Schleiz is located 30 kilometers north of Hof and 145 kilometers southwest of Dresden at the intersection of Routes 2 and 94. At the beginning of the battle, elements of Drouet's division clashed with Tauentzien's outposts. When Tauentzien became aware of the strength of the advancing French forces, he began a tactical withdrawal of his division. Joachim Murat assumed command of the troops and began an aggressive pursuit. A battalion-sized Prussian force to the west was cut off and suffered heavy losses. The Prussians and Saxons retreated north, reaching Auma that evening.

The twin battles of Jena and Auerstedt were fought on 14 October 1806 on the plateau west of the river Saale, between the forces of Napoleon I of France and Frederick William III of Prussia. The decisive defeat suffered by the Prussian Army subjugated the Kingdom of Prussia to the French Empire until the Sixth Coalition was formed in 1813.

Before 1806, Saxony was part of the Holy Roman Empire, a thousand-year-old entity that had become highly decentralised over the centuries. The rulers of the Electorate of Saxony of the House of Wettin had held the title of elector for several centuries. When the Holy Roman Empire was dissolved in August 1806 following the defeat of Emperor Francis II by Napoleon at the Battle of Austerlitz, the electorate was raised to the status of an independent kingdom with the support of the First French Empire, then the dominant power in Central Europe. The last elector of Saxony became King Frederick Augustus I.

The Battle of Czarnowo on the night of 23–24 December 1806 saw troops of the First French Empire under the eye of Emperor Napoleon I launch an evening assault crossing of the Wkra River against Lieutenant General Alexander Ivanovich Ostermann-Tolstoy's defending Russian Empire forces. The attackers, part of Marshal Louis-Nicolas Davout's III Corps, succeeded in crossing the Wkra at its mouth and pressed eastward to the village of Czarnowo. After an all-night struggle, the Russian commander withdrew his troops to the east.

After defeating the Prussian army in the autumn of 1806, Emperor Napoleon entered partitioned Poland to confront the Russian army, which had been preparing to support the Prussians until their sudden defeat. Crossing the River Vistula, the French advance corps took Warsaw on 28 November 1806.

The Battle of Pułtusk took place on 26 December 1806 during the War of the Fourth Coalition near Pułtusk, Poland. Despite their strong numerical superiority and artillery, the Russians suffered the French attacks, before retiring the next day having suffered greater losses than the French, disorganizing their army for the rest of the Year.

In the Battle of Mohrungen, most of a First French Empire corps under the leadership of Marshal Jean-Baptiste Bernadotte fought a strong Russian Empire advance guard led by Major General Yevgeni Ivanovich Markov. The French pushed back the main Russian force, but a cavalry raid on the French supply train caused Bernadotte to call off his attacks. After driving off the cavalry, Bernadotte withdrew and the town was occupied by the army of General Levin August, Count von Bennigsen. After demolishing the army of the Kingdom of Prussia in a whirlwind campaign in October and November 1806, Napoleon's Grande Armée seized Warsaw. After two bitterly fought actions against the Russian army, the French emperor decided to place his troops into winter quarters. However, in wintry weather, the Russian commander moved north into East Prussia and then struck west at Napoleon's left flank. As one of Bennigsen's columns advanced west it encountered forces under Bernadotte. The Russian advance was nearly at an end as Napoleon gathered strength for a powerful counterstroke.

While the Battle of Allenstein resulted in a French field victory and allowed for a successful pursuit of the Russian army, it failed to produce the decisive engagement that Napoleon was seeking.

he combat of Hof (6 February 1807) was a rearguard action fought between the Russian rearguard under Barclay de Tolly and the advancing French during the Russian retreat before the battle of Eylau. Both sides suffered significant losses at Hof. The Russians lost over 2,000 men, two standards and at least five guns (Soult claimed that they had lost 8,000 men). Soult admitted to 2,000 casualties amongst his own men and Murat's cavalry must also have suffered losses in the cavalry fight.

The Battle of Friedland was a major engagement of the Napoleonic Wars between the armies of the French Empire commanded by Napoleon I and the armies of the Russian Empire led by Count von Bennigsen. Napoleon and the French obtained a decisive victory that routed much of the Russian army, which retreated chaotically over the Alle River by the end of the fighting.

The Treaties of Tilsit were two agreements signed by Napoleon I of France in the town of Tilsit in July 1807 in the aftermath of his victory at Friedland. The first was signed on 7 July, between Emperor Alexander I of Russia and Napoleon I of France, when they met on a raft in the middle of the Neman River. The second was signed with Prussia on 9 July. The treaties were made at the expense of the Prussian king, who had already agreed to a truce on 25 June after the Grande Armée had captured Berlin and pursued him to the easternmost frontier of his realm. In Tilsit, he ceded about half of his pre-war territories.

Key Findings:

• Napoleon cemented his control of Central Europe
• Napoleon had created French sister republics, which were formalized and recognized at Tilsit: the Kingdom of Westphalia, the Duchy of Warsaw as a French satellite state and the Free City of Danzig
• Tilsit also freed French forces for the Peninsular War.
• Russia becomes an ally of France
• Prussia looses approximately 50% of her territory
• Napoleon is able to enforce the Continental System in Europe(with the exception of Portugal)