Ten months later Napoleon decided to leave Elba. He landed at Cannes on 1 March 1815 and proceeded to Paris gathering support along the way. He arrived there on 20 March, overthrew the restored Bourbon monarch, Louis XVIII and began remobilizing his veterans as well as drafting over 2.5 million new men into his army. The Seventh Coalition of opposing nations also began remobilizing.

      Assessing the threat he faced, Napoleon saw the greatest was the Anglo-Allied forces commanded by Wellington located in Belgium southwest of Brussels and a nearby Prussian army commanded by Blucher. The Austrian and other German armies were located to the south along the Rhine. The Russian army was enroute but still a substantial distance away. He decided on a pre-emptive strike against the allies in Belgium driving the British into the sea and the Prussians out of the war. On 16 June a French army of some 128, 000 achieved the surprise he sought by defeating the Prussians at Ligny and blocking Wellington's ability to support Blucher by engaging the British at Quatre Bras. With the Prussian retreat the British were also forced to fall back to the area of the village of Waterloo. According to the Duke of Wellington, the battle that ensued was "The nearest-run thing you ever saw in your life."

      It rained heavily overnight on 17 June, so Napoleon delayed giving battle until noon on 18 June to allow the ground to dry. Wellington's army, positioned across the Brussels road on the Mont St Jean escarpment, withstood repeated attacks by the French, until in the evening when they counter-attacked and drove the French from the field. Simultaneously the Prussians arrived in force and broke through Napoleon's right flank. Finally, the French army left the battlefield in disorder, allowing Coalition forces to enter France and restore Louis XVIII to the French throne. On 24 June Napoleon abdicated to the British and was exiled to Saint Helena, where he died in 1821.