Beau Geste is a 1924 novel by Percival Christopher Wren. It details the adventures of the orphaned brothers Michael (also known as Beau), his twin Digby, and their younger brother John. This novel is most known for its popularization of the French Foreign Legion. It has been adapted for both theater and cinema.
This novel provides examples of the following tropes:
The Ace: Michael, especially in the eyes of his idolizing brothers.
Badass Army: The French Foreign Legion, as romanticized by the book.
Bedouin Rescue Service: Near the end of the book when the heroes are wandering through the Sahara after deserting from the Legion.
Bittersweet Ending: While John lives and the real reason for the loss of the Blue Water is revealed, his brothers and friends are dead.
Cunning Linguist: One of the old Legionnaires whom the brothers look up to reveals that he speaks English as well as several other languages. Also, Michael decides that he and his brother ought to learn Arabic and they end up becoming fluent in it after a while, which comes in handy later.
Honor Before Reason: Michael's reason for leaving England to enlist in the Legion, and that of his brothers for joining him after they find out what he's done.
Impractically Fancy Outfit: The famous Legionnaire's uniform, which at the time consisted of a blue tunic, red breeches and a white cap, all made of heavy wool. This makes them sitting ducks to the native tribesmen who are dressed much more practically for the climate.
Legion of Lost Souls: Is it ever. Most of the Legionnaires are criminals and/or conscripts who had no choice but to enlist. The three brothers stand out for their upper-class roots and education.
Locked Room Mystery: The theft of the stone. Also, the scene at the beginning where the relief forces that arrive at Zinderneuf (which has been burned and all of the garrison killed)
Michael's nickname, Beau Geste, meaning "beautiful gesture" in French. Takes on Fridge Brilliance once the truth about the Blue Water is revealed. It turns out Lady Patricia sold the stone and arranged for a duplicate made; Michael decided to stage a theft of the stone to deflect blame from his aunt, and thus was a beautiful gesture to her.
Lejaune, the commander of Fort Zinderneuf, whose name means "the yellow" in French. Yellow is not a colour with positive overtones in English, chief among them being cowardice and Lejaune does end up betraying the heroes during the siege of Zinderneuf before earning himself a Karmic Death. Also noteworthy in that a discharge notice in the French army during this period was known as a "cartouche jaune" (yellow paper), symbolically implying that Lejaune was unfit for service in the regular army.
Reality Is Unrealistic: Comparing Beau Geste with Simon Murray's Legionnaire, a real-life account of the French Foreign Legion, it is apparent that the point where Lejaune draws the line on his Drill Sergeant Nasty treatment of the legionnaires is about the point where the real-life sergeants start.