Turks to the Empire of the Caliphate became very similar to the relations of the Medes to the last Babylonian Empire fourteen centuries before. In the eleventh century a group of Turkish tribes, the Seljuk Turks, came down into Mesopotamia and made the Caliph their nominal ruler but really their captive and tool. They conquered Armenia. Then they struck at the remnants of the Byzantine power in Asia Minor. In 1071 the Byzantine army was utterly smashed at the battle of Melasgird, and the Turks swept forward until not a trace of Byzantine rule remained in Asia. They took the fortress of Nicæa over against Constantinople, and prepared to attempt that city.
The Byzantine emperor, Michael VII, was overcome with terror. He was already heavily engaged in warfare with a band of Norman adventurers who had seized Durazzo, and with a fierce Turkish people, the Petschenegs, who were raiding over the Danube. In his extremity he sought help where he could, and it is notable that he did not appeal to the western emperor but to the Pope of Rome as the head of Latin Christendom. He wrote to Pope Gregory VII, and his successor Alexius Comnenus wrote still more urgently to Urban II.
This was not a quarter of a century from the rupture of the Latin and Greek churches. That controversy was still vividly alive in men’s minds, and this disaster to Byzantium must have presented itself to the Pope as a supreme opportunity for reasserting the supremacy of the Latin Church