‘Some battles change nothing. Waterloo changed almost everything.’On the 18th June 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 British at Quatre-Bras and the Prussians at Ligny. The Allies were in retreat.The blood-soaked battle of Waterloo would become a landmark in European history, to be examined over and again, not least because until the evening of the 18th, the French army was...