The Song of the Crusade is a poem, written in Occitan, which covers the events of the war against the Cathars of the Languedocs during the period 1204 to 1218. The Song () was attributed to William of Tudela, but research has revealed two distict authors. William wrote only the first third, and an unknown author the second two-thirds (the switch occurs between laisses 131 and 132 in the middle of a speach by King Peter II of Aragon). While William was clearly wholly in sympathy with the Roman Church, and the French crusaders, the other author was clearly a close companion of the Count of Toulouse, whose heart was with the armies of the South, if not with the religion of the Cathars. Both write in alexandrine verse. William introduces his new rhyme in the half line of the last line of each laisse. His successor repeats the last line of each laisse at the first line of the next.
The second part of the poem is more skillfully written, more dramatic and more moving, bringing alive the horrors and cruelty of Holy War. Throughout the crusaders are referred to, as in other Occitan literature, as the "French" - a constant reminder that the people of the Languedoc were not then French and had no reason to think of themselves as such.