On this day, 5th February 1576, King Henry IV of Navarre renounced or abjured his Catholic ties to become a bona fide Huguenots Protestant; forever and always, no takesy-backsies, done and dusted, for sure.
Raised a Protestant by his mother, but baptised a Catholic, one could say he was playing both sides from the start. Both sides of the French Wars of Religion, that he was a part of from a very young age and engaged in for most of his adult life.
His abjuration of Catholicism was a direct result of a Protestant massacre, at his wedding no less. St. Bartholomew's Day massacre took place a few days after the knot was tied, and several thousand protestants who had come for the wedding were killed.
No wonder he turned his back to the Catholics.
But, as you might have guessed, that only lasted a while. A few years later, Henry was named the heir presumptive of France due to lineage. Being a stout Protestant, and leader of the Huguenots, this caused issues with majority Catholic France.
And so begins the War of Three Henrys, but that's a topic for another time. Long story short, Henry essentially won the war, but was halted by the Catholic League and was unable to take Paris.
So what would anyone do faced with this conundrum? Why, simply convert of course! In July 1593 he became a bona fide Roman Catholic; forever and always, no takesy-backsies, done and dusted, for sure.
Understandably this peeved his allies, the Huguenots and Queen Elizabeth I, but it did mean that his claim to the French crown was a bit more legitimate than before. It also ended his excommunication by the Pope, won him favour with the French populace and the Catholic League, and secured his place on the throne.
All it took was a few words muttered under his breath at the Cathedral of Chartres. (And a few battles and killings and such but never mind that)
In the end historians assert, to no one's surprise, that Henry was a stout Calvinist (Protestant), and only changed his formal religion to suit political needs. It's how he was raised, so who can blame him?
It is funny to see how nothing has really changed, has it? Catholics will probably be fighting religious wars until the end of time...