On the 16th of July, 1212, was fought the great battle which broke the Moorish power in Spain. During the two centuries before fresh streams of invasion had flowed in from Africa to yield new life to the Moslem power. From time to time in the Mohammedan world reforms have sprung up, and been carried far and wide by fanaticism and the sword. One such body of reformers, the Almoravides, invaded Spain in the eleventh century and carried all before it. It was with these that the Cid Campeador had to deal. A century later a new reformer, calling himself El Mahdi, appeared in Africa, and set going a movement which overflowed the African states and made its way into Spain, where it subdued the Moslem kingdoms and threatened the Christian states. These invaders were known as the Almohades. They were pure Moors. The Arab movement had lost its strength, and from that time forward the Moslem dominions in Spain were peopled chiefly by Moors. Spain was threatened now as France had been threatened centuries before when Charles Martel crushed the Arab hordes on the plains of Tours. All Christendom felt the danger and Pope Innocent III. preached a crusade for the defence of Spain against the infidel. In response, thousands of armed crusaders flocked into Spain, coming in corps, in bands, and as individuals, and gathered about Toledo, the capital of Alfonso VIII., King of Castile. From all the surrounding nations they came, and camped in the rich country about the capital, a host which Alfonso had much ado to feed. Mohammed An-Nassir, the emperor of the Almohades, responded to the effort of the Pope by organizing a crusade in Moslem Africa. He proclaimed an _Algihed_, or Holy War, ordered a massacre of all the Christians in his dominions, and then led the fanatical murderers to Spain to join the forces there in arms. Christian Europe was pitted against Moslem Africa in a holy war, Spain the prize of victory, and the plains of Andalusia the arena of the coming desperate strife. The decisive moment was at hand. Mohammed left Morocco and reached Seville in June. His new levies were pouring into Spain in hosts. On the 21st of June Alfonso began his advance, leading southward a splendid array. Archbishops and bishops headed the army. In the van marched a mighty force of fifty thousand men under Don Diego Lopez de Haro, ten thousand of them being cavalry. After them came the troops of the kings of Aragon and Castile, each a distinct army. Next came the knights of St. John of Calatrava and the knights of Santiago, their grand-masters leading, and after them many other bodies, including troops from Italy and Germany. Such a gallant host Spain had rarely seen. It was needed, for the peril was great. While one hundred thousand marched under the Christian banners, the green standard of the prophet, if we may credit the historians, rose before an army nearly four times as large.