On June 18, 1815, the armies of France, Britain, and Prussia descended upon a quiet valley south of Brussels. In the previous three days, the French army had beaten the Prussians at Ligny and fought the British to a standstill at Quatre-Bras. The Allies were in retreat. The little village north of where they turned to fight the French army was called Waterloo. The blood-soaked battle to which the town gave its name would become a landmark in European...