Why did the Catholic Holy League oppose Henry of Navarre becoming king of France?

The Catholic Holy League opposed Henry of Navarre’s accession to the French throne primarily because he was a Protestant leader, and the League was fundamentally committed to the defense of the Roman Catholic religion.12

When Henry of Navarre became the heir to the French crown in 1584 following the death of the duc d’Anjou, the prospect of a Protestant king triggered a revival of the Holy League. The League, led by the house of Guise and supported by Spain, sought to exclude him from the succession to prevent a Protestant from ruling a Catholic nation.12

The opposition was rooted in deep religious conflict during the Wars of Religion. The League viewed Henry as a threat to the Catholic faith and considered the reigning monarch, Henry III, too tolerant of Huguenots. The League’s resistance only began to wane after Henry of Navarre—the first king from the house of Bourbon—converted to Roman Catholicism in 1593, effectively removing the primary religious objection to his reign.123