He comes from the second branch of Lorraine-Vaudemont, ducal family of Lorraine and therefore related to the Guise.
He married, in 1579, Marie of Luxembourg, Duchess of Penthièvre, heir to this Breton Duchy, which gave him, among other things, a justification for being appointed Governor of Brittany in 1582, by his brother-in-law, the King of France Henri III. The latter had indeed married Mercœur’s sister, Louise de Vaudémont.
Having become head of the League after the assassination of the Duke of Guise in 1588, he aspired to restore the former Breton duchy to his benefit, ignoring the royal power weakened by the Wars of Religion.
Leader of the League, he had most of the province on his own, although Brittany felt little concerned by the movements of the League.
The Ligueurs did not recognize the authority of Henri IV, still a Protestant at that time, when he became king of France on the death of Henri III.
Philippe Emmanuel of Lorraine,
Duke of Mercoeur.
Neptunia n ° 66
Mercœur was a staunch Catholic, radical and devious. His ambition and his religious conviction soon led him to openly oppose Henry IV. From 1589 to 1595 a confused civil war ensued in Brittany.
The inhabitants of Blavet, attached to the royal cause, rejected the requests of the Leaguers. The Duke of Mercœur then came in person to attack Blavet. His troops were exhausted in vain on the entrenchment that closed the isthmus, from Locmalo to the Driasker (the Old Trench). The whole population heroically participated in the defense of the city.
Mercœur then appealed to Spain who sought to take advantage of the disorders in France with the hope of obtaining the crown for his daughter, arguing that Isabelle was the granddaughter of Henry II. Philip II, King of Spain, sent him an expeditionary force of 6,000 men under the leadership of don Juan de Aquila.
In October 1590, the Spaniards landed at St Nazaire, moved on Mercœur’s advice to Blavet and took Hennebont. It was then that three or four ships landed soldiers from Mercœur’s party in the besieged city. The inhabitants, cut to pieces, regardless of age or sex, found themselves unable to flee, having the choice only between the edge of the sword or drowning. Mercoeur set fire to what was left of the city (only the new Saint-Pierre church escaped the flames), then he offered the ruined square to the Spaniards with whom he was linked. The latter were to occupy Blavet for eight years.
He won Craon’s victory over the troops of Henri IV (March 1592).
In 1595, Charles de Cossé-Brissac, was appointed by the king lieutenant-general, then governor of Brittany and received the mission to subdue Mercœur.
Little by little, Mercœur found himself cornered and had to submit to Henry IV. He negotiated his surrender against a large sum and the marriage of his daughter Françoise with César, Duke of Vendôme, bastard of Henri IV, who would become governor of Brittany.
Mercœur, eager to put his life at the service of religion, left in October 1599 to fight the Turks who threatened to invade Europe. Appointed generalissimo, he could not defeat the Ottomans, but besieged and stormed Albe Royale on the Ranzia. Suffering from “purple fever”, he died in Nuremberg, a Protestant city, in 1602.
His body was brought back to France and buried in Lorraine, and, according to the wishes of the deceased, his heart was handed over to the Capuchins of Nantes.
While François de Sales delivered a vibrant funeral oration, in great pomp at Notre-Dame de Paris, the Protestants by the voice of Aubigné noticed that:
” Unhappy in the wars against the Reformed,
Mercœur had fought the infidels with unparalleled happiness “.