Vesta, go back and revisit World History. The Crusades happened because the Muslims were invading France, Spain, England, Wales & Scotland to raid and capture slaves and rape, pillage and plunder. It was a retaliatory strike, NOT an invasion as you seem to infer.
I understand what you are saying.
The Crusades was also headed up by the Christian Church to not only stop the threat to their faith but to gain the riches that lay in the midst of the Muslim world.
Many a religious war drew in the fighters with the excuse of a threat to their faith, but, the end goal was the riches that could be gotten for the Christian church.
How else to get man power to fight a war that the pheasants knew nothing about.?
Our own Civil War could not have drawn the North to leave their family's and farms to fight had it not been for the Pastors that turned the war into a " On would Christian Solder" belief that the fight was for the freedom of others.
Why would entire towns have their men and boys leave their familys to fight for the rights of complete strangers had it not become a matter of religious belief.
Some small towns that supplied the man power knew nothing about slavery, few people fighting had ever seen or met a slave. Some diarys from that time tell of the writers first encounter with a person of color, and they wrote of the shock and surprise.
I believe that the manpower from the north were simple men that could not read or write but attended church twice a week and when they believed they were doing the work of God went forth and did so.
Those that could read and write were advanced as Sargents or supply men, record keepers, very valuable. These men were never in front of a file closer.
For some reason I believe this was the first war that was fought and won on religious belief. The man power had no interest in riches or property, they were there to right a wrong that they knew nothing about except what they were told by their preachers.
Interesting war, the South was fighting for states rights and the North gave up their blood to prevent this as they fought for the rights of the very same people they would in later years restrict from the same rights as they had.
All war is complicated and has many sides and views.
When things got really bad we had the draft riots in New York the carnage had gotten so bad that men refused to be a part of it.
Sherman did the old slash and burn policy marching into Atlanta, he did not need to do that, but it kept his troops entertained so they would not desert and go home, or head out west.
General Hooker incouraged the ladys to come into camp and keep his troups under control.
Hell of a war, and this may come again in the future if we ever have to face a show down between faiths.