Today in 1815, the forces of the Seventh Coalition engaged and defeated Napoleon for the last time, and put an end to over twenty years of constant war in Europe. A combined Coalition force led by the Duke of Wellington, and a Prussian force under Marshal von Blucher, met Napoleon's own at Waterloo, outside Brussels (then part of the Netherlands, now Belgium).
The occurrence of the battle, and Coalition victory were not assured. The Prussians had been delayed by a defeat at Ligny (where von Blucher was nearly killed), and were hesitant to re-engage so quickly, thus forcing Wellington to begin plans to retreat to Brussels. However, a recovered von Blucher agreed to divide his forces - most to march towards Waterloo, and a smaller force to stop the arrival of Imperialiste reinforcements. However, the timely arrival of von Blucher was questionable. Thus, at the beginning of the battle, with no Prussian troops, the opposing forces were equally matched at roughly 70,000 men each.
Beginning at somewhere between 10:30 and 11:30, Napoleon initiated the attack against Wellington, with infantry and cavalry (and largely ineffective artillery) that slowly succeeded in pushing back Wellington. By mid-afternoon, Napoleon was actually all but the victor of the battle, having broken through Wellington's slowly crumbling lines. Finally, it was around this time that von Blucher arrived with the main column of the Prussian forces that halted the breaking of the Coalition forces and began to turn the tide of the battle. Realizing that the Prussians would eventually overwhelm him, Napoleon ordered a desperate attack by the Imperial Guard against Wellington, hoping to break the linkages between the Coalition and the Prussians - which nonetheless failed. By evening, whatever French forces couldn't retreat had surrendered.
Although Napoleon would not surrender himself for nearly another month, there was now nothing to stop the Coalition from marching to Paris and restoring Bourbon King Louis XVIII onto the French throne. This time, when Napoleon was exiled, it was to St. Helena, a remote island in the Atlantic under British control and 2,000 miles from the nearest mainland.
As a curiosity, in European and American politics, candidates typically lay out what they plan for their first hundred days in office. This recalls the Napoleonic restoration (referred to by historians as the Hundred Days) - from his arrival in Paris on 20 March 1815, Napoleon was able to rebuild his army, and use it to nearly defeat the combined powers of Europe on 18 June (91 days). He abdicated as Emperor of the French on 22 June (95 days) and left Paris on 29 June (102 days). Louis XVIII was restored in Paris on 8 July, 111 days after its loss to Napoleon. Thus modern politicians invoke Napoleon in their campaigns (although none come close to his achievements).