The morning of 18 June 1815 was overcast and wet in the fields south of Brussels, near a small ridge by the village of Waterloo. The Duke of Wellington surveyed his position and remarked that it would be a close run thing — perhaps the closest run thing he had ever seen. He was not wrong. By the end of that day, Napoleon Bonaparte's military career and political life would be over; but for several desperate hours in the afternoon, with the French Imperial Guard advancing in the gathering smoke and the expected Prussian reinforcements nowhere yet in sight, the outcome had been genuinely uncertain.
Napoleon had returned from his first exile on Elba in March 1815, rallying France to his banner in the Hundred Days that terrified Europe and forced the allied powers to mobilise again. He understood that his only hope was to defeat the British and Prussian armies in Belgium before the Austrians and Russians could bring their larger forces to bear. Speed was essential. He crossed into Belgium on 15 June, defeated a Prussian force at Ligny on the 16th and sent Marshal Ney against Wellington at Quatre Bras on the same day — an inconclusive engagement that allowed Wellington to fall back to his chosen defensive position on the ridge of Mont-Saint-Jean.
Wellington's tactical genius lay in his use of the reverse slope — placing his infantry behind the crest of the ridge, out of sight of French artillery, while his skirmishers and cavalry screened the front. The French artillery bombardment that preceded each attack caused far fewer casualties than Napoleon intended. The attacks themselves were absorbed by British and allied infantry in close-packed formations, their musketry devastating the columns as they crested the ridge and presented themselves as targets.
The crisis came in the early evening when Napoleon committed his Imperial Guard — the elite of his army, troops who had never been broken in battle. Wellington responded by revealing regiments he had concealed behind the crest and delivering a devastating volley at close range. The Guard broke. As the cry went up that the Guard was retreating, the entire French army began to dissolve. At the same moment, the Prussian army under Blücher arrived in force on Napoleon's right flank, transforming retreat into rout. Wellington rode along his ridge and gave the order for a general advance. The battle was over.
Waterloo ended the quarter century of near-continuous European war that had begun with the French Revolution. For Britain, it inaugurated what historians call the Pax Britannica — a century of global commercial and maritime supremacy in which the Royal Navy dominated the world's sea lanes, British capital financed global development, and British manufactured goods penetrated every market. The Congress of Vienna, which followed Napoleon's final defeat, redrew the map of Europe in ways favourable to British strategic interests. For the rest of the nineteenth century, no European power seriously threatened British global dominance. Wellington's victory at Waterloo had bought Britain a century of exceptional power.
