From the eighth century AD, and even before (some facts and prove) the coexistence of religions that best identifies the West (Christianity) and the Middle East (the Muslims) lived hours of growing enmity. The unstoppable advance of Islam, and the gradual divergence and intolerance had led both to an open ideological warfare and expansion. After the triumph in 1071 of the Seljuk Turks into Syria and Palestine, and the subsequent capture of Jerusalem, the supposed threat of so-called infidels was almost a step into Europe. Alexius, emperor of Byzantium, had spread in the Western world its alarm. And Pope Urban II, in the famous Council of Clermont, was his assistance in organizing the First Crusade (1096-1099) under the motto: Deus vult! ("God wills it!). a However, this papal initiative was not the first attempt to fight against Islam.
In 1095, a French priest called Peter the Hermit, or Peter of Amiens, had incited the faithful to take up arms and recover the holy places with a disastrous journey of 12,000 men (consisting of peasants, artisans and nobles middle) that was massacred by the forces of the Seljuk Sultanate of Rum. Just this new and great empire, was the cause and trigger pop crossover. Consider: After breaking the mythical known Roman Empire thanks to the expansive force of the Germanic migrations, one of its two divisions, Byzantine, had seized the eastern part of Europe. Weak, sensual, and corrupt nature to settle firmly in the area was soon threatened by their own dissensions and the challenge of Croatians, Normans (who had snatched the south of Italy) and above all, the Seljuks , a people of Turkish origin and a warrior as military-grade or more advanced than their counterparts in the West.