During the first religious wars in France, Mayenne participated in several military actions against the Huguenots. After the assassinations (1588) of his brothers, Henri, duc de Guise, and Louis, cardinal de Lorraine, Mayenne emerged as the leader of the Catholic party. In 1589 he assumed the presidency of the general council of the Holy League, and, after the assassination of Henry III, Mayenne supported the old Cardinal de Bourbon as “Charles X” in his bid for the crown in opposition to the Huguenot claimant, Henry of Navarre (King Henry IV, 1589–1610). Although he wanted a Catholic ruler for France, Mayenne curbed the extremists who sought to put the Spanish infanta Isabella on the French throne; in 1593 he summoned a meeting of the States General in Paris, which upheld the principles of the Salic law of succession against Isabella's claim. In September 1595 Mayenne finally submitted to Henry IV; by the Articles of Folembray (January 1596) Mayenne retained Chalon, Seurre, and Soissons for six years, his followers kept the honours and offices he had granted them, his own debts were settled up to 35,000 crowns, and his son was made governor of Île-de-France. Thereafter he remained on excellent terms with Henry IV.