In December of 1584, the news that all of Catholic France dreaded spread across the kingdom. The Duc d’Anjou, the youngest son of Henry II and the heir to the throne, was dead. Since his elder brother, Henry III looked to die childless, the next in line for the throne was the heretic, Henry of Navarre. Seeing the inevitable, Henry III sent the Duc d’Epernon to Navarre to beg and cajole him to convert to Catholicism.
Navarre refused to convert, and Phillip II sprang into action. Don Bernardino de Mendoza, still smarting from being expelled from England, headed towards the Guise seat of Joinville to force their Catholic allies in France to commit to an alliance. The following January, both Guise and his corpulent brother, the Duc de Mayenne, committed themselves, their brother the Cardinal de Guise, and their cousins the Ducs d’Aumale and Elbeuf to what would become a “perpetual union.”
The Guise desperately wanted to include some outsiders, notable Duc Henry’s brother in law, the Duc de Nevers. Married to the Duchesse de Guise’s elder sister, Henriette, Louis de Nevers wavered back and forth between joining the new Catholic League that sprung up from the treaty and remaining loyal to Henri III. While Nevers’ heart remained with the League, he decided to at least outwardly remain loyal to Henry III.
The Guise relations pledged to root out any heresies and sects within the kingdom and the Netherlands. Not only were the Guise committing themselves to warfare in their own country, they were allowing Phillip to use them as hired guns to fight his Protestant battles in the Netherlands. Flaunting the French succession laws, the Guise pledged to prevent any “heretic” prince of the blood from taking the throne of France. Acting as agents of the French crown, the Guise further agreed to cease any plans to trade in the New World. In between, the Guise would help Phillip recover Cambri.
Phillip promised to give the Guise an initial 600,000 crowns to finance their wars against Protestant claimants, with 50,000 crowns a month until the hostilities ceased. Once the Catholic claimant, the Cardinal de Bourbon, took the throne, the Guise would repay Phillip all of the money.
When Henry III heard that the Guise had entered into a treaty with a foreign sovereign he was livid. The new Catholic League had acted as the official government of France, and did so under his royal nose. Once the terms of the treaty became public, Henri’s rivalry with the new League became public knowledge and his monarchy became threatened.