Battle of Austerlitz
At the Battle of Austerlitz (December 2, 1805), during the War of the Third Coalition, a French force of approximately 73,000 under Napoleon decisively defeated a joint Russo-Austrian force of over 89,000, commanded by Russian General Kutuzov with General von Weyrother commanding the Austrian contingent. The French suffered 9,000 casualties and the Russo-Austrian armies lost about 25,000 men that where killed, wounded or captured. The Russians withdrew from Austria and the Austrians signed the Treaty of Pressburg (26 December 1805), conceding substantial territories to the French.
The Battle of Austerlitz followed on Napoleon's significant defeat of the Austrian General Mack at Ulm. In an unprecedentedly (for that era) rapid concentration of French forces, Napoleon essentially defeated Mack by maneuver, resulting in the surrender of a major Austrian force protecting the northern approach to Vienna, and subsequently leading to the capture of the Austrian capital.
Austerlitz is sometimes known as the "Battle of Three Emperors" because it represented the clash of Napoleon I, Tsar Alexander I of Russia, and Emperor Francis II of the Holy Roman Empire on the battlefield [were they on the field or merely in the theater?].
See also: Napoleonic Wars