Excellent question. The Crusades were waged, with varying degrees of success, in response to Islamist aggression. From the time of Mohammed, Muslims had sought to conquer the Christian world.
They did a pretty good job of it, too. After a few centuries of steady conquests, Muslim armies had taken all of North Africa, the Middle East, Asia Minor, and most of Spain. In other words, by the end of the eleventh century the forces of Islam had captured two-thirds of the Christian world.
Palestine, the home of Jesus Christ; Egypt, the birthplace of Christian monasticism; Asia Minor, where St. Paul planted the seeds of the first Christian communities: These were not the periphery of Christianity but its very core. And the Muslim empires were not finished yet. They continued to press westward toward Constantinople, ultimately passing it and entering Europe itself.
As far as unprovoked aggression goes, it was all on the Muslim side. At some point what was left of the Christian world would have to defend itself or simply succumb to Islamic conquest. The First Crusade was called by Pope Urban II in 1095 in response to an urgent plea for help from the Byzantine emperor in Constantinople.
Urban called the knights of Christendom to come to the aid of their eastern brethren. It was to be an errand of mercy, liberating the Christians of the East from their Muslim conquerors. In other words, the Crusades were from the beginning a defensive war.
The entire history of the eastern Crusades is one of response to Muslim aggression.
IGNORANCE. Since the Roman Catholic RULED the WORLD during the times of the Crusades. The Christian church or Protestantism was fought for by HENRY VIII for his own personal reasons--and had nothing to do with religion but politics.
Someone must have been absent in history class. Then again--I am forgetting my manners, the parts of the Crusades were not taught in some denominational churches--I leave that up for research in historical data.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.