Henri Coiffier was the second son of Antoine Coiffier Ruze, marquis d'Effiat, marshal of France, and was introduced to the court of Louis XIII by Richelieu, who had been a friend of his father and who hoped he would counteract the influence of the queen's favourite Mile, de Hautefort.
Owing to his handsome appearance and agreeable manners Henri Coiffier soon became a favourite of the king, and was made successively master of the wardrobe and master of the horse. After distinguishing himself at the siege of Arras in 1640, Cinq- Mars wished for a high military command, but Richelieu opposed his pretensions and the favourite talked rashly about overthrowing the minister. He was probably connected with the abortive rising of the count of Soissons in 1641; however- that may be, in the following year he formed a conspiracy with tne duke of Bouillon and others to overthrow Richelieu. This plot was under the nominal leadership of the king's brother Gaston of Orleans. The plans of the conspirators were aided by the illness of Richelieu and his absence from the king, and at the siege of Narbonne Cinq-Mars almost induced Lcuis to agree to banish ' his minister. Richelieu, however, recovered, became acquainted with the attempt of Cinq-Mars to obtain assistance from Spain, and laid the proofs of his treason before the king, who ordered his arrest. Cinq-Mars was brought to trial, admitted his guilt, and was condemned to death. He was executed at Lyons on the 12th of September 1642. It Is possible that Cinq-Mars was urged to engage in this conspiracy by his affection for Louise Marie de Gonzaga (1612 - 1667), afterwards queen of Poland, who was a prominent figure at the court of Louis XIII. ; and this tradition forms part of the plot of Alfred de Vigny's novel Cinq-Mars.
