Great Britain and Russia signed the Treaty of Saint Petersburg, creating an offensive alliance aimed at opposing Napoleon’s French Empire. This agreement helped form the diplomatic foundation for the Third Coalition that France would face later in 1805.
Napoleon was crowned King of Italy in Milan, reinforcing French influence in northern Italy and alarming Austria. The move added to fears that Napoleon intended to reshape the European balance of power by expanding French control beyond France’s borders.
Austria formally joined the coalition aligned against France, linking its war planning with Britain and Russia. This step made a major continental war increasingly likely and encouraged Austria to prepare an army to move into southern Germany.
Napoleon shifted his main field army (the Grande Armée) away from the Channel coast, where it had been preparing for a possible invasion of Britain. The rapid march east aimed to defeat Austria before large Russian forces could fully join the fighting.
Napoleon’s forces began the Ulm campaign, a series of fast marches and coordinated movements in southern Germany. The goal was to surround and cut off an Austrian army positioned near Ulm, rather than fight a slow, set-piece battle.
French forces under Murat and Lannes defeated an Austrian corps at Wertingen, an early clash in the Ulm campaign. The victory helped disrupt Austrian screening forces and supported Napoleon’s larger plan to encircle the main Austrian army.
Marshal Michel Ney defeated Austrian forces at Elchingen, limiting Austrian escape routes and increasing pressure on the trapped army at Ulm. This battle was a key step in turning Napoleon’s operational maneuver into a full encirclement.
The Austrian force under General Mack surrendered at Ulm, ending the campaign in a decisive French victory. This removed a major Austrian army from the war and opened the way for Napoleon to advance toward Vienna.
Off Cape Trafalgar, the British Royal Navy defeated the combined French and Spanish fleet. Although it did not decide the land campaign in Central Europe, it prevented France from challenging British sea power and reduced French strategic options.
In northern Italy, Masséna’s French army fought Archduke Charles at Caldiero. The fighting mattered because it shaped whether Austrian forces in Italy could threaten French positions or reinforce the defense of Austria’s core territories.
Near Dürenstein (Dürnstein), Russian forces struck parts of the French corps under Mortier along the Danube. The hard fighting slowed the French pursuit and showed that Russia’s army could still challenge Napoleon’s advance even after Austria’s Ulm defeat.
French advance elements captured a key bridge over the Danube at Vienna through deception and a rapid move. Holding Vienna helped Napoleon secure supplies and a base for operations, while forcing the coalition armies to regroup farther north and east.
At Schöngrabern (Hollabrunn), Russian rear-guard forces under Bagration fought to slow the French advance. The delay helped Kutuzov’s main army withdraw and link up with other coalition troops before a decisive battle could be forced.
Napoleon’s army defeated combined Russian and Austrian forces at Austerlitz in Moravia (now in the Czech Republic). The victory broke the coalition’s momentum on land and made Austria’s continued participation in the war difficult to sustain.
An armistice followed shortly after Austerlitz, signaling Austria’s move toward leaving the coalition. This pause in major fighting created the conditions for formal peace negotiations and set the stage for a treaty that reshaped central Europe.
Austria and France signed the Treaty (Peace) of Pressburg, ending Austria’s role in the War of the Third Coalition after Ulm and Austerlitz. The treaty imposed major territorial losses and political concessions on Austria, strengthening Napoleon’s influence in Germany and Italy and setting up further changes to the European order.
War of the Third Coalition and the 1805 Campaign (1805)