Eastern Europe had been lost through an ever-widening breach in Christian practice from the fifth to the eleventh century. The Eastern Church used the Greek language in its liturgy; that of the West used the Latin language. The former remained more dependent upon the state; the latter grew less dependent. Minor differences of doctrine appeared. And the Eastern Christians thought the pope was usurping unwarrantable prerogatives, while the Western Christians accused the Oriental patriarchs of departing from their earlier loyalty to the pope and destroying the unity of Christendom. Several attempts had been made to reunite the Catholic Church of the West and the Orthodox Church of the East, but with slight success. In 1500, the Christians of Greece, the Balkan peninsula, and Russia were thought to be outside the Catholic Church and were defined, therefore, by the pope as schismatics. [Sidenote: Mohammedanism] Far more numerous and dangerous to Catholic Christianity than the schismatic Easterners were the Mohammedans. Mohammed himself had lived in Arabia in the early part the seventh century and had taught that he was the inspired prophet of the one true God. In a celebrated book,-- the Koran,--which was compiled from the sayings of the prophet, are to be found the precepts and commandments of the Mohammedan religion. Mohammedanism spread rapidly: within a hundred years of its founder's death it had conquered western Asia and northern Africa and had gained a temporary foothold in Spain; thenceforth it stretched eastward across Persia and Turkestan into India and southward into central Africa; and in the fourteenth and fifteenth centuries, as we have seen, it possessed itself of Constantinople, the Balkans, Greece, and part of Hungary, and threatened Christendom in the Germanies and in the Mediterranean. [Sidenote: Western Heresies]