Which battle ended Napoleon's rule in 1815?

Waterloo, on 18 June, and it was very close. Wellington called it the nearest run thing you ever saw in your life. The French had the better army on paper and Napoleon had beaten the Prussians at Ligny two days earlier; the plan depended on keeping them beaten, and Marshal Grouchy took 33,000 men off in pursuit and failed to find them.

The Prussians arrived on the French right in the afternoon, which is the reason the day ended as it did - Wellington was holding a ridge and running out of army. Heavy rain the night before had also delayed the French attack for hours while the ground dried, hours the Prussians used to march.

The consequence lasted a century. The settlement that followed produced a European balance that avoided a general continental war until 1914, which is the longest such stretch in modern history. Napoleon was exiled to St Helena in the South Atlantic, one of the most remote inhabited places on Earth, and died there in 1821 - of stomach cancer, most probably, though arsenic in his hair has kept the poisoning theories alive for two centuries.