In short, 400 years of mostly unanswered aggression from Muslims against Christians. It was at that point that Pope Urban called for a Crusade to free the Holy Land. Then followed about 200 years of Christian warfare to push back the Muslims. Eventually, Europe tired of this and stopped the crusades. The Muslims went on to destroy the Byzantine empite in 1453, and took Constantinople. Further aggression saw Muslims in eastern Europe and as late as 1683, they laid seize to the city of Vienna in Central Europe. The concept of jihad (holy war) is still very much part of the Muslim thinking. But we haven't had a crusade in about 700 years.
Anyone who acts like the Crusades is some sort of moral nadir of human civilization is woefully ignorant. They were brief defensive wars waged against an enemy that has wage aggressive war against the West for 13 centuries.
I am well aware of history, I was trying to point out how pathetic the position of my son’s prof was and how revisionist history is be pushed by the communists/liberals professors in our colleges today.
Thanks though