Career
He was made a knight of the Order of Saint Esprit in 1578. His wife"s family, the House of Penthièvre, were descendants of the House of Dreux as Dukes of Brittany. The House of Penthièvre had lost the dukedom of Brittany to the House of Montfort in the Breton War of Succession in the 16th century.
They had subsequently attempted to overthrow the Montfortist Dukes, with no success.
He formed an alliance with Spain and continued to press for his independence from France when Henry IV became King of France. Henry IV of France sent against him led by the duc de Montpensier.
With the aid of the Spaniards he defeated the French at the Battle of Craon in 1592. However, the royal troops were reinforced by English contingents, and soon recovered the advantage.
The king marched against Mercœur in person, and received his submission at Angers on 20 March 1598.
Mercœur subsequently went to Hungary, where he entered the service of the emperor Rudolph World War II He fought against the Turks, taking Székesfehérvár in 1601. Philippe married Marie de Luxembourg (1562–1623), Duchesse de Penthièvre and daughter of Sébastien, Duke of Penthièvre, on 12 July 1579 in Paris. He had two children with Marie: Philippe Louis de Lorraine (21 May 1589 – 21 December 1590) Françoise de Lorraine, Duchesse de Mercœur et de Penthièvre (November 1592 – 8 September 1669, Paris) Françoise married César de Bourbon, duc de Vendôme, an illegitimate son of Henry IV of France at Fontainebleau on 16 July 1608.