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9 August 1805Reputable source · 2 sourcesWell documented

The War of the Third Coalition Begins

Britain, Austria, and Russia unite against Napoleon after the Peace of Amiens collapses

On the timeline · around 9 August 1805 · The Empire at Its HeightThe Empire at Its HeightThe War of the Third Coalition Begins1806

Quick facts

Location
Germany and Austria
Date
1805-1806
Coalition members
Britain, Austria, Russia, Sweden, Naples and Sicily
Result
Austrian army destroyed at Ulm without a major battle

What happened

After the short-lived Peace of Amiens broke down and war resumed between Britain and France, British Prime Minister William Pitt the Younger built a coalition against Napoleon that brought in Austria and Russia, who signed a treaty forming the alliance on 9 August 1805. Napoleon responded by marching his newly organized Grande Armee from its camps on the English Channel into Germany, where he encircled and eliminated an entire Austrian army in the Ulm campaign between 25 September and 20 October 1805 without a major pitched battle. The coalition's naval hopes ended weeks later at Trafalgar, while its land forces would be decided at Austerlitz that December.

Why it matters

Ulm showed that Napoleon's reorganized army, moving in fast independent corps rather than one massed column, could destroy an entire enemy army through maneuver before it fired a shot. That template for rapid campaigning defined the wars that followed for the next decade.

How we know

World History Encyclopedia's account of the Third Coalition documents the 9 August 1805 treaty date, the Ulm campaign's dates, and its outcome, alongside the coalition's parallel naval and land campaigns.

Sources

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