Henry IV Statue
On 13th April 1598, King Henry IV ratified the Edict of Nantes, granting protestants, the right to practice their faith. Henry used to be a protestant himself but had to renounce and convert to Catholicism in order to become King of France.
This treaty ended the Religion Wars that had decimated France for nearly 40 years. Not to mention the Religion Wars involving other European countries which will start again later during the reigns of Louis XIII and Louis XIV. Ultimately, the latter will revoke the Edict of Nantes, thus ending religious tolerance.
Historians' estimates vary, but it could be as many as half a million Huguenots converted to Catholicism by force during the reign of Louis XIV, while another half a million left France and relocated to a more tolerant country.