Events of 1211.
The Meridional forces (under Count of Toulouse and his allies the Count of Foix and Savaric de Mauléon) were besieging Castelnaudary where Simon de Montfort and his French Crusader army were holed up. The meridional's encampment was strong but did not entirely surround the walls of the town.
Following the advice of Hugues de Lacy, Simon sent some knights, among them Guy de Lévis and Bouchard de Marly, to seek as many reinforcements as possible. Martin d'Algai and his mercenaries rode to reinforce them, but the Count of Foix planned to ambush them near the castle of Saint-Martin, 3 miles from Castelnaudary. Simon got wind of this and sent Guy de Lucy, Simon de Neauphle, Roard de Donges and 40 other knights to their rescue.
The Count of Foix returned to Castelnaudary bringing more troops which, when the battle started, he organised in 3 battallions (heavy cavalry at the centre, lighter cavalry on one wing, infantry on the other). It appears that Foix acted on his own, without support from the other lords.
Outnumbered, Martin d'Algai's mercenaries fled, which incited some of Foix's troops to plunder the baggage train and leave the battlefield while the fierce cavalry battle continued.
Simon, who had seen this, dashed out of Castelnaudary with 60 knights leaving only 5 knights and the infantry to defend the castle against de Mauléon's attacks.
Now the Count of Foix was in danger. His troops fled in disarray.
Severe losses had been inflicted on both sides.
The following day, Simon left Castelnaudary, leaving only a small garrison.
A few days later, the Meridionals raised the siege.
Both sides claimed victory.