Creation of a generation of peace
The 200-year-long Battle of Waterloo drastically altered the course of history. One of the most astounding things to happen in both European and global history.
If Waterloo was Britain's greatest military victory, as is sometimes lauded, then the fight itself cannot be blamed for that accomplishment. Most military historians concur that neither Napoleon's nor Wellington's strategic skills were particularly on display during the fight.
If anyone lives and repels the French, Wellington informed his men, they would be guaranteed a generation of peace. As he had predicted, it did occur.
Napoleon was defeated by the Seventh Coalition, who also set the groundwork for a united Europe and reduced the death toll, ushering in a new era of peace, this is one of the best significance of the battle of Waterloo.