Off Cape Trafalgar, Nelson cut Villeneuve's combined Franco-Spanish fleet in two: eighteen ships lost, none on the British side, and Nelson killed in his victory. The imperial navy never recovered and any landing in England became impossible. Unable to win at sea, Napoleon would turn to the economic weapon of the Continental System.

The West Indies plan

To cover a landing in England, command of the Channel was needed for a few days. The 1805 plan was ambitious: Villeneuve was to draw Nelson's fleet to the West Indies, return to Europe ahead of him, join the Brest and Ferrol squadrons and sail up to Boulogne. The manoeuvre failed off Cape Finisterre in July; Villeneuve took refuge in Cadiz. On 26 August the Emperor broke camp at Boulogne: the invasion was abandoned before the battle.

21 October

Ordered to sail for Naples and threatened with dismissal, Villeneuve left Cadiz with thirty-three Franco-Spanish ships. Nelson, with twenty-seven, abandoned the traditional line ahead and attacked in two perpendicular columns to cut his enemy into three. The signal hoisted on the Victory — "England expects that every man will do his duty" — preceded five hours of mêlée.

The outcome was final: eighteen Allied ships taken or destroyed, none lost by the British; Admiral Gravina died of his wounds and Villeneuve was captured. Nelson, hit by a marksman from the Redoutable, died in his victory.

Two centuries of consequences

The imperial navy never recovered: the rebuilt ships stayed blockaded in port until 1814. Britain held the sea for a century, and with it world trade and the financing of the coalitions.

Unable to win on the water, Napoleon decreed the Continental System a year later: the war moved to economic ground, where it would ruin the Empire more surely than any army.