It was hoped that this signal proof of piety on the King’s part would break at last the inflexible infidelity of the race. ♦638♦ The Church also decreed that every king in the future should at his coronation take a solemn oath to continue the persecution of heretics. But persecution presupposes a perfect accord between the civil authority and the ecclesiastical; and, as has sometimes happened since, the secular power in Spain recognised certain limits to its capacity for obeying the spiritual. Chintilla died in 642, and later sovereigns refused to carry out the decrees of the Church, while others tried to do so in vain. The Jews were too useful to be dispensed with. Political necessity overruled religious bigotry, and Spain, as every other country in Europe, continued to present the strange spectacle of a proscribed sect flourishing under the very eyes of the judges who had repeatedly pronounced its doom. Despite the manifold disabilities under which the Jews laboured, they remained and multiplied in the peninsula, the pseudo-converts practising Judaism in secret; some of the avowed Jews refuting the arguments of their assailants in polemical treatises; all nursing a sullen hatred of their rulers and waiting for an opportunity of gratifying it. Such an opportunity offered itself in the Arab invasion, and the Mohammedan Caliphs found in these suffering children of a kindred race and religion ready and valuable allies. It is not improbable that the fear of such an alliance between the followers of Mohammed and those of Moses had intensified among the Christians of Spain the anti-Jewish feeling which found vent in the violent persecution of the Jews during the years immediately preceding the conquest of the peninsula. If so, the Spaniards by their treatment of the Jews created the situation which they feared. The Mohammedan invasion was prepared by the intrigues of the Jews of Spain with their co-religionists in Africa, who exposed to the Saracens the weaknesses of the Visigothic kingdoms. Tarik, the Mohammedan conqueror, in his triumphant career through the peninsula, ♦711♦ after the battle of Xeres, where Roderic the last of the Visigothic kings had fallen, was everywhere supported by the Jews. Cordova, Granada, Malaga, and other cities were entrusted to the safe-keeping of the Jews, and Toledo was betrayed to the invader by the Jews, who, while the Christian inhabitants were assembled in church praying for divine help, ♦712♦ threw the gates open to the enemy, acclaiming him as a saviour and an avenger.