The Fourth Coalition fought in a war against Napoleon's French Empire from 1806–1807. The coalition was defeated.
Countries in the Coalition included Prussia, Russia, Saxony, Sweden, and Great Britain. Several members of the coalition had previously been fighting France in the Third Coalition, and there wasn't any peace in between wars. On October 9, 1806, Prussia joined a new coalition, fearing that France was becoming more powerful after it defeated Austria and established the Confederation of the Rhine. Prussia and Russia prepared for a new campaign. Prussian troops moved to Saxony.
On 14 October 1806, the French defeated the Prussian army at the Battle of Jena-Auerstadt. Then French forces occupied Prussia and captured Berlin. Later they advanced towards Poland and Russia. On 7-8 February 1807, the French and Russian armies fought the Battle of Eylau. There was no clear winner. On 14 June 1807, the French defeated the Russians at the Battle of Friedland. In July 1807, France made peace with Russia, ending the war. This left Napoleon as ruler of most of western and central Europe. The exceptions were Spain, Portugal, Austria, and a few smaller states. These were able to remain independent.
Even though the Fourth Coalition came to an end, Britain remained at war with France. Later that year, the Peninsular War started.
The participants of the War of the Fourth Coalition. Blue: The Coalition and their colonies and allies. Green: The First French Empire, its protectorates, colonies and allies.