What was the political and religious reasons for the early crusades?

The Crusades were launched by the Popes (leaders of the catholic church). The European Kings' Armies March to Places that were occupied by Arab Tribes. The Crusades were unsuccessful, they ended giving more land to the Arabs. One of the only lasting resault was that Europe gained more technology.

Dictionary.com describes it as : "any of the military expeditions undertaken by the Christians of Europe in the 11th, 12th, and 13th centuries for the recovery of the Holy Land from the Muslims."