1588 left Mayenne at the head of the Catholic party. Head of the Catholic League The ambassador of the Republic of Venice, Giovanni Mocenigo, states that Mayenne had warned Henry III that there was a plot afoot to seize his person and to send him by force to Paris. At the time of the murder he was at Lyon, where he received a letter from the king saying that he had acted on his warning, and ordering him to retire to his government. Mayenne professed obedience, but immediately made preparations for marching on Paris. After a vain attempt to recover those of his relatives who had been arrested at Blois, he proceeded to recruit troops in his government of Burgundy and in Champagne. Paris was devoted to the house of Guise and had been roused to fury by the news of the murder. Mayenne entered Gournay-sur-Marne in 1589, while Paris would not fall until 1590. He found it dominated by representatives of the sixteen quarters of Paris, all staunch supporters of the League. He formed a council general to direct the affairs of the city and to maintain relations with the other towns faithful to the League. Each quarter sent four representatives, and Mayenne added representatives of the various trades and professions of Paris in order to counterbalance this revolutionary element. He constituted himself "lieutenant-general of the state and crown of France," taking his oath before the parlement of Paris. In April Mayenne advanced on Tours. Henry III in his extremity sought an alliance with the Huguenot, Henry of Navarre (the future Henry IV of France), and the allied forces drove the leaguers back, and had laid siege to Paris when the assassination of Henry III by a Dominican friar changed the face of affairs and gave new strength to the Catholic party. King-maker Mayenne was urged to claim the crown for himself, but he was faithful to the official programme of the League and proclaimed Charles, Cardinal de Bourbon, at that time a prisoner in the hands of Henry IV, as Charles X of France, although this numbering is not accepted by historians. Henry IV retired to Dieppe, followed by Mayenne, who joined his forces with those of his cousin Charles, Duke of Aumale, and Charles II de Cossé, comte de Brissac, in a succession of fights in the neighbourhood of Arques (September 1589). He was defeated and out-marched