The second siege of Toulouse was the largest and longest one attempted between 1209 and 1218. In duration and intensity it rivaled famous crusader sieges in Outremer and others in western Europe of the High Middle Ages. During its great length it exhibited virtually every type of military activity possible in the Middle Ages, from blockade, machine warfare, and infantry assault to hand-to-hand combat and amphibious attacks.

While heretofore Peter Vaux-de-Cernay has been our main source for so many details of the crusade, the quality and quantity of his coverage steeply declines for this period. The Cistercian chronicler devotes what only amounts to thirteen sub-headings' worth of text to this nine-month siege. While William of Puylaurens offers us more than he usually does, his account of the siege totals only one chapter of the printed text. As a critical source the Chanson comes into its own for this period, and we are dependent on it for many incidents that occurred during the siege. The Anonymous spends almost one third of the entire poem just on the second siege of Toulouse. When relying on this source so heavily we must keep in mind a repeated caveat: there are many – too many – invented conversations and speeches in the Anonymous's account. Still, when we get past the hyperbole, much of what he writes probably reflects what people actually thought and said.