July 16, 1212
As a consequence of the Christian victory at Las Navas de Tolosa, the power of the Almohads, the Berber regime that had dominated Muslim Spain (Al-Andalus) from the mid-twelfth century, was shattered, enabling the Christians to take over almost all of southern Spain in the ensuing forty years.
The battle was the result of a crusade against the Muslim infidel in Spain organized by Alfonso VIII of Castile, Rodrigo Ximénez de Rada, archbishop of Toledo (d. 1247), and Pope Innocent III (1198-1216). French, Provençal, and Italian knights and soldiers eventually arrived at Toledo to join up with crusaders brought by the kings of Aragón and Navarre, as well as the army assembled by Alfonso VIII of Castile.
Once the combined armies left Toledo and headed south, however, most of the "foreign" crusaders deserted, finding the heat and outbreaks of disease unbearable.
The Christian armies arrived at Las Navas de Tolosa, which lies to the northeast of Córdoba and Jaén, on Friday, July 13. During the ensuing Saturday and Sunday, only small skirmishes took place, but on the morning of Monday, July 16, the Christian armies attacked the Almohads. The Castilians and the Military Orders were flanked on the right by Sancho VII of Navarre with the Navarrese troops and urban militias from Ávila, Segovia, and Medina, and on the left by the king of Aragón and his army. Initially the Almohad vanguard had to retreat, but when the bulk of its army entered the battle, it seemed as if the Christians would be defeated. It was at this point that Alfonso VIII advanced and the kings of Aragón and Navarre converged from the flanks. The combined Christian attack was decisive, even reaching the chains and the guards defending the headquarters tent of the Almohad leader. A Muslim retreat quickly became a rout, and the Almohad leader, Muhammad an-Nasir, fled toward Jaén that same night. Among the enormous booty collected was the so-called Muslim "flag of Las Navas," which survives in the monastery of Las Huelgas in Burgos.