The Cusades were fought in different places and at different times, from just before the 12th century to just before the fourteenth. That being said, one can generalize that the Crusades fought in the Holy Land were an effect, and an outcome, of political pressures often justified in religious terms. For instance, it is often said that the Crusades were driven by Christian ideas about Jerusalem and who should control it. European's could perhaps understand, in simple religious terms, the aesthetic principle that the holy city of Jerusalem "should" be under the control of Christian powers. But the idea that this was the "reason" for the Crusades washes over more complex political pressures which were not directly religious in origin. For example, there was the high cost of imports from outside of Europe. European leaders saw Jerusalem as a "base" outside Europe which could be used as a distribution point for foreign goods that would "cut out" expensive middle men and other merchants. Another economic/political goal was the seeking wealth through adventurism. Another goal was to give violent young knights something to do, so that they would not cause leaders trouble in their home countries.