[3] The extant work only survives in a fragment (two parchment sheets that had been used as a binding of a book[3]) of 661 octosyllable[2][3] (unusual for a chanson de geste) verses in assonanced laisses (conserved in the Royal Library of Belgium in Brussels[3]) written in a central France dialect,[3] dating from c. 1130, and that form the end of a much longer poem.
[2] The content of the entire poem can be inferred from two sources: Dating of the composition of the chanson is based on: The reconstructed plot is as follows: The young French lord Isembart is cruelly persecuted by the French court and his uncle, king Louis, and he goes into exile in England, joining the Saracen king Gormond and renouncing Christianity.
In the battle, after a series of victorious combats, Gormond falls to Louis, but the king is himself mortally injured when he tries to remain on his horse.
Four days later, the Saracens give up the battle and Isembart dies, returning to Christianity in his last breaths.
[2] The poem appears based on an invasion of Norsemen who burned the Abbey of Saint-Riquier in February 881 and were defeated by Louis III six months later at Saucourt-en-Vimeu.