Today is the 800th anniversaryof the battle of Muret when the army commanded by Simon de Montfort the elder (the father of King Henry III's brother-in-law from Hell) defeated the army of King Peter II of Aragon, who was killed in the battle, and Count Raymond VI of Toulouse in the Albigensian Crusade. It is claimed that Montfort and his 700 knights sweptaside up to 50,000 albigensian forces. Whatever the exact figures the loss of King peter in the first charge by the Catholic forces appears to have demoralised the Cathars and their allies. To the Catholics the victory was seen as miraculous. The site of the battle, which now lies in the outer suburbs of Toulouse, is now largely built over. There is an online account of the battle, with links to related sites, here.
Along with Las Navas de Tolosa in 1212 and Bouvines in 1214 Muret was one of this group of battles which determined the political contours of western Europe in the thirteenth century.
The Lay Dominicans website has this about the battle of Muret and the Rosary:
Just before the battle of Muret, September 12, 1213, Saint Dominic was again found in the council that preceded the battle. During the conflict, he knelt before the altar in the church of Saint-Jacques, praying for the triumph of the Catholic arms. So remarkable was the victory of the crusaders at Muret that Simon de Montfort regarded it as altogether miraculous, and piously attributed the victory to the prayers of Saint Dominic. In gratitude to God for this decisive victory, the crusader erected a chapel in the church of Saint-Jacques, which it is said he dedicated to Our Lady of the Rosary. (It would appear, therefore, that the devotion of the rosary, which tradition says was revealed to Saint Dominic, had come into general use about this time.)
The whole artcicle from their website can be seen here.