 His growing unpopularity led to an assassination attempt on him, followed by a second fall from grace in 1726 when he was the subject of a lettre de cachet.He spent 18 months in the Bastille, was released in 1728, and retired to his estates in Champagne, where he entered into a long correspondence with Voltaire.Pâris-Duverney became involved in military affairs again during the War of the Polish Succession.