The League immediately began to exert pressure on Henry III of France. Faced with this mounting opposition (spurred in part because the heir to the French throne, Henry of Navarre, was a Huguenot) he canceled the Peace of La Rochelle, re-criminalizing Protestantism and beginning a new chapter in the French Wars of Religion. However, Henry III also saw the danger posed by the Duke of Guise, who was gaining more and more power. On the Day of the Barricades, Henry III was forced to flee Paris, which resulted in Guise becoming the de facto ruler of France. Afraid of being deposed, the King decided to strike first. On December 23, 1588, Henry III's guardsmen assassinated the Duke and his brother, Louis II while the Duke's son, Charles of Lorraine, was imprisoned in the Bastille.