Defeat for Napoleon at hands of British Admiral Nelson, ending his chances of invading England; Napoleon resorted to the Continental System.

• A. Waterloo
• B. Austerlitz
• C. Jena
• D. Trafalgar

Answer: (D)

Controlling the seas determines whether an invasion can even be attempted. Admiral Nelson’s victory at Trafalgar in 1805 crushed Napoleon’s plan to invade England by sea, because the British navy remained dominant and prevented the French and their allies from assembling a fleet capable of crossing the Channel. With invasion no longer feasible, Napoleon pivoted to economic warfare, implementing the Continental System to block British trade and try to starve Britain economically.

That shift makes Trafalgar the best answer because it directly ties Napoleon’s failed invasion plan to his subsequent resort to the Continental System. The other battles listed are important Napoleonic conflicts—Austerlitz and Jena were land victories for Napoleon, and Waterloo was his final defeat on land—but none involve Nelson or a failed invasion of Britain, so they don’t fit the scenario described.