Final answer:
Henry IV of France, previously a Protestant as Henry of Navarre, converted to Catholicism to ascend to the throne and later issued the Edict of Nantes to grant religious freedom to French Protestants.
Step-by-step explanation:
Henry IV of France, originally Henry of Navarre, was involved in the religious conflicts of his time, specifically those related to the Protestant Reformation in France. During the War of the Three Henrys, after the death of the other two contenders (Henry III and Henry of Guise), Henry of Navarre stood as the sole candidate for the French throne.
Although he was a Protestant, he joined the Roman Catholic Church to end the strife and secure his position as king, a move that eventually led to the issuing of the Edict of Nantes in 1598. This edict granted liberty of conscience and liberty of worship to the French Protestants, known as Huguenots, marking a significant step towards religious toleration in France.