In September 1213 in southwestern France two Christian armies faced each other off. One was led by King Peter II of Aragon, who after his glorious victory against a Muslim army at the Battle of Las Navas de Tolosa the previous year, was not only one of the most respected monarchs of Christendom but a favoured son of the Church. The other army was composed of crusaders, mainly from northern France, fighting on behalf of the Pope to root out heresy from the French region of Languedoc.