After the Arabian Empire had become fully established, there arose to the northeast of Bagdad, the Moslem capital, a number of Turkish tribes that were among the more recent converts to Mohammedanism. Apparently they took the Mohammedan religion as embodied in the Koran literally and fanatically, and, considering nothing beyond these, sought to propagate the doctrine through conquest by sword. They are frequently known as Seljuks. It is to the credit of the Arabs, whether in Mesopotamia, Africa, or Spain, that their minds reached beyond the Koran into the wider ranges of knowledge, a fact which tempered their fanatical zeal, but the Seljuk Turks swept forward with their armies until they conquered the Byzantine Empire of the East, the last branch of the great Roman Empire. They had also conquered Jerusalem and {320} taken possession of the holy sepulchre, to which pilgrimages of Christians were made annually, and aroused the righteous indignation of the Christians of the Western world. The ostensible purpose of the crusades was to free Palestine, the oppressed Christians, and the holy sepulchre from the domination of the Turks. It must be remembered that the period of the Middle Ages was represented by fancies and theories and an evanescent idealism which controlled the movements of the people to a large extent. Born of religious sentiment, there dwelt in the minds of Christian people a reverence for the land of the birth of Christ, to which pilgrims passed every year to show their adoration for the Saviour and patriotism for the land of his birth. These pilgrims were interfered with by the Mohammedans and especially by the Seljuk Turks. The Turks in their blind zeal for Mohammedanism could see nothing in the Christian belief worthy of respect or even civil treatment. The persecution of Christians awakened the sympathy of all Europe and filled the minds of people with resentment against the occupation of Jerusalem by the Turks. This is one of the earliest indications of the development of religious toleration, which heralded the development of a feeling that people should worship whom they pleased unmolested, though it was like a voice crying in the wilderness, for many centuries passed before religious toleration could be acknowledged.