Renaud and his three brothers were sons of Aymon de Dordogne. They flee from the court of Charlemagne after Renaud kills one of Charlemagne's nephews in a brawl. A long war follows, during which Renaud and his brothers remain faithful to the chivalrous code of honour despite their sufferings, until Charlemagne is prevailed on by his paladins to make terms.
The four brothers are pardoned on condition that Renaud go to Palestine on the Crusades, and that their magic horse Bayard, which could expand its size to carry all four brothers on its back, be surrendered to Charlemagne. Charlemagne orders that the magic horse be drowned by chaining it to stones and throwing it in a river; but the horse escapes and ultimately returns to the brothers. Renaud, after further adventures on the Crusades, returns to Cologne, where he ultimately dies defending the builders of a shrine to St Peter.
Charlemagne is not portrayed sympathetically in this cycle of stories. He is portrayed as vengeful and treacherous; he is fooled by the sorcerer Maugris; the sympathy of the storyteller is clearly with the four brothers, but ultimately feudal authority is upheld. Renaud, as Rinaldo, is an important character in Orlando Furioso by Torquato Tasso. During the German occupation of Belgium during World War II, the story of Les Quatre Fils Aymon was made into a play that was banned by the German authorities, because of the sympathy it displayed for resisting authority; the play was performed underground and became quite popular.