The Congress of Vienna of 1815
After the fall of Napoleon, the leaders of each of the victorious powers of the Coalition Britain, Austria, Prussia, and Russia, plus the Ottoman Empire met in the Austrian capital of Vienna to discuss how to restore stability to France and Europe. The mastermind of the peace conference was Clement von Metternich, an Austrian aristocrat, who believed strongly that Europe had seen too much turmoil in the past generation and needed to re-establish a traditional form of social and political order. His policy, in short, was to shore up the nobility and monarchs across Europe.
To this end, Metternich invited to Vienna representatives of the kings of Bavaria, Poland, Belgium and Spain, each of which had recently been restored to their thrown after having been forced out by Napoleon. He was also instrumental in the restoration to the French throne of the Bourbon family, in the person of King Louis XVIII, formerly the Count d'Artois who had led the emigrated nobles' army since 1792. (Louis XVI of course had been beheaded and his son, who never reigned but was considered by royalists to be Louis XVII, had died in a Revolutionary prison.)
The Congress set forth a policy which would become known as the Concert of Europe, in which the so-called great powers (namely, France, Britain, Prussia, Austria, Russia and to a lesser extent, the Ottoman Empire) would act together (that is, in "concert") to ensure that none of them would ever be threatened by a Revolution at home or invasion by another country. Metternich further proposed that the great powers would support the monarchy and aristocracy in any of the lesser powers, such as Poland, Spain, Bavaria, Belgium or Denmark.