text: In one appearance, this character investigates the fortifications at Belle Ile.
full_question: In one appearance, this character investigates the fortifications at Belle Ile. This character dies shortly after being made a Marshal in The Vicomte of Bragelonne. When he is working under Monsieur des Essart, this character has an affair with Constance Bonacieux, who is a maid of Queen Anne. At the beginning of the first novel in which this character appears, his introduction letter for Monsieur de Treville is stolen by Comte de Rochefort. This character defeats Cardinal Richelieu's troops with a group of soldiers that uses the motto "All for one, one for all." For 10 points, name this character who befriends Athos, Porthos, and Aramis in The Three Musketeers.
first_sentence: In one appearance, this character investigates the fortifications at Belle Ile.
raw_answer: D'Artagnan