The War of the Third Coalition, which spans from 1803 to 1806, sees the defeat of an alliance of Austria, Portugal, Russia, and others by France and its client states under Napoleon I.

Great Britain is the only country still at war with France after the Treaty of Pressburg.

Britain, fearing a French invasion, secures mastery of the seas by destroying a Franco-Spanish fleet at Trafalgar in October.

The war, however, is decided on the continent, and the major land operations that seal the swift French victory involve the Ulm Campaign, a large wheeling maneuver by the Grand Army lasting from late August to mid-October that captures an entire Austrian army, and the decisive French defeat of a combined Russo-Austrian force under Tsar Alexander I at the Battle of Austerlitz in early December.Austerlitz effectively brings the Third Coalition to an end, although later there is a small side campaign against Naples, which also results in a decisive French victory at the Battle of Campo Tenese.

On December 26, 1805, Austria and France sign the Treaty of Pressburg, which takes the former out of the war, reinforces the earlier treaties of Campo Formio and Lunéville, makes Austria cede land to Napoleon's German allies, and imposes an indemnity of 40 million francs on the defeated Habsburgs.

Russian troops are allowed to head back to home soil.

Victory at Austerlitz also permits the creation of the Confederation of the Rhine, a collection of German states intended as a buffer zone between France and the rest of Europe.

In 1806, the Holy Roman Empire ceases to exist when Holy Roman Emperor Francis II keeps Francis I of Austria as his only official title.

These achievements, however, do not establish a lasting peace on the continent.

Austerlitz has driven neither Russia nor Britain, whose armies protect Sicily from a French invasion, to settle.

Meanwhile, Prussian worries about growing French influence in Central Europe will spark the War of the Fourth Coalition in 1806.