Excerpts from Books and Wikipedia
"In 1160 Muslim Spain came under the control of the militant Almohad dynasty of Morocco. . . . By 1211 the Christian position had become so bad that Pope Innocent III proclaimed a crusade against the Almohads. . . . When they fell on the Almohad army at Las Navas de Tolosa, they achieved total surprise, killing or capturing 100,000 Muslim soldiers. Muslim power in Spain never recovered from the devastating defeat. For the remainder of the century, the Christian kingdoms made steady advances at Muslim expense until by 1294 only Granada remained." [Furtado: 1001 Days] "Perhaps the most negative effect of Almohad ideology and its practice in Spain was the harshness embodied in the Almohads' stridently monolingual, purist Muslim regime. . . . The political instability and disunity created by this clash of Muslim ideals and styles coincided with the extraordinarily heightened papal power and influence of Innocent III during his years as pontiff, 1198 to 1216. In 1212, with Innocent's encouragement and support, and with the provocations provided by the Almohads' heightened hostility, the diverse and fractious Christians of Spain joined with troops from the north to march against the Muslims . . ."