Emmanuel Armand de Richelieu, Duke of Aiguillon

Emmanuel-Armand de Vignerot du Plessis-Richelieu, duc d'Aiguillon (31 July 1720 – 1 September 1788), was a French soldier and statesman, and a nephew of Armand de Vignerot du Plessis, 3rd Duke of Richelieu. He served as the Secretary of State for Foreign Affairs under King Louis XV.

He was the son of Armand-Louis de Vignerot du Plessis, duc d'Aiguillon (1683–1750), and until the death of his father, he was known at court as the duc d'Agénois. He entered the army at the age of seventeen, and at the age of nineteen was made colonel of the regiment of Brie. His marriage in 1740 with Louise Félicité de Brehan, daughter of the Comte de Plélo, coupled with his connection with the Richelieu family, gave him an important place at court.

Upon the death of King Louis XV's mistress, Madame de Vintimille, in childbirth in 1741, the king's best friend (and the duc d'Agénois' uncle), the manipulative Duke of Richelieu, began to cast about for another candidate to fulfil his royal friend's desires, as he did not want Madame de Vintimille's older sister, Madame de Mailly, to regain the king's affections. He eventually decided upon the younger sister of both Madame de Mailly and Madame de Vintimille, Marie Anne, the widow of the marquis de La Tournelle.

At a masked ball on Shrove Tuesday, 1742, Richelieu led Marie Anne up to the king and introduced them. The beautiful marquise, however, at first rejected the royal advances. She already had a lover, the young duc d'Agénois, and was not inclined to give him up even for the king's sake. As a result, the king conspired with Richelieu, who was the duc d'Agénois' uncle, to rid himself of the young suitor. Richelieu was quite anxious to do anything to bring about a liaison between the king and Madame de La Tournelle, because he knew that Madame de Mailly did not view him in a kindly light. The result of their deliberations was that the king, in imitation of the biblical David, sent his rival to fight the Austrians in Italy during the War of the Austrian Succession. The young duke was seriously wounded at the siege of Château-Dauphin (1744). Unlike the husband of Bathsheba, however, the duc d'Agénois recovered from his injuries and returned to the court in glory.

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