Though by all evidence a good Protestant, Henri was at root ambitious. His well-timed political marriage to Marguerite paid major dividends when Charles IX died (in 1574, aged 24), making Henri second behind Charles' younger brother Henri. Alas, in 1589 said king (now known as Henri III) was assassinated (while under Henri de Navarre's suddenly inept protection) by the monk Jacques Clement ... and there was Henri de Navarre, pulling a Fortinbras face.
Four years of civil and religious war led to a brokered compromise; in 1593 Henri converted and in 1594 he finally secured the throne with his coronation at Chartres. "Paris," he is reputed to have said, "is worth a mass."
Only four years after that, Henri put an end to the Wars of Religion by promulgating the Edict of Nantes, which granted the Protestants freedom of worship and 100 places to practice it. But nearly a hundred years later, the unholy alliance between the Catholic Church and the French monarchy reawakened as, in 1685, Henri's grandson Louis XIV, a thorough-going Catholic egotist misled by wishful reports into believing that Protestantism had virtually died out, revoked the Edict of Nantes, demanding that the remaining Huguenots convert or leave. They all fled France, many more of them than Louis had been led to believe. As befits the man who coined "L'etat, c'est moi", Louis first tried to stop them (I gave you a choice, how dare you take it), then persecuted those who converted so they could remain, then was shocked and astonished that his economy stumbled with the loss of so many high-quality silversmiths, sculptors, and merchants. (Exactly the same sequence had played out in Spain two hundred years earlier when the Catholic Kings Ferdinand and Isabella expelled all the Mariscos after the completion of the Reconquista in 1492, and later the Jews.)