Complex sentence: In the first year of her reign, Jeanne d'Albret called a conference of beleaguered Huguenot ministers which led to her declaring Calvinism the official religion of her kingdom after publicly embracing the teachings of Calvin on Christmas Day 1560.
Split into simpler sentences: In the first year of her reign, Jeanne d'Albret called a conference of beleaguered Huguenot ministers. She went to declare Calvinism the official religion of her kingdom after publicly embracing the teachings of Calvin on Christmas Day 1560.