Four hundred years after the Muslim expansion, the Christians of Europe struck back. "It is the Will of God" was the slogan of the crusaders who assembled in Western Europe. At the end of the first expedition - personally sacralized by the Pope - the blood-drenched conquest of Jerusalem took place, in the year 1099. In recollection of the "jihad", Muslim leaders pooled their resources to win back the lost territories. The events that occurred had a long-term influence on religious affairs. Hundreds of thousands of crusaders died, but also a large number of Islamic warriors, as well as civilians - Christians, Jews and Muslims.