The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
Initially, the Crusades were not a religious movement on the part of Europeans against Islam, but in important ways, the Crusades were driven by religious faith.
Between 1096 and 1291, Muslims and Christian fought each other to control what they considered to be sacred sites in the Middle East. By 1096, Muslim troops had captured Constantinople and the pope had to intervened to call all western European nations to unite against Muslims and recover the sacred sites. Many Christian groups were formed to defend property and sacred sites such as the case of the Knights Templar.