a. The Crusaders were the Christian soldiers who fought a series of holy wars known as the Crusades against the Turkish Muslims, between the 11th and 13th centuries CE. The Crusades were fought because, in the 11th century CE, the Turks conquered the Holy Land of Jerusalem and attacked the ruler of Constantinople. Hence, the Pope organised armies to reoccupy the Holy Land.
b. The capture of Jerusalem allowed the Christians to hold the Holy Land for nearly a century, and they also gained other strongholds in the Near East. However, in spite of this success, the Crusades failed to establish a permanent Christian kingdom in the Holy Land.
c. Yes, religion played a very important role in the minds of the Crusaders. The Crusades were called 'Holy Wars' because they were fought with the religious objective of reclaiming the Holy Land of Jerusalem for Christianity. The wars were waged by the armies of the Pope, the spiritual leader of the Christians. The religious zeal motivated thousands of Christians to undertake the long and dangerous journeys to fight in these wars.