You have misunderstood your history as regards the Crusades. The territory that the European knights were fighting in had been part of the Eastern Roman Empire for over a thousand years until it was captured by the Muslim armies. Those armies didn't stop there, they continued on right to France (where they were defeated otherwise we would all be speaking Arabic). The first crusade was a response to a request from the Eastern Roman Emperor for help in defending his Empire from the Muslim armies and not a war of aggression. It was the Muslims who were the aggressors during the crusades and both sides fought in terrible ways but the series of wars we know as the crusades were not started by Europeans but were started by the Muslim armies and were, from a European point of view, wars of defence and not of aggression.
You have misunderstood your history as regards the Crusades. The territory that the European knights were fighting in had been part of the Eastern Roman Empire for over a thousand years until it was captured by the Muslim armies. Those armies didn't stop there, they continued on right to France (where they were defeated otherwise we would all be speaking Arabic). The first crusade was a response to a request from the Eastern Roman Emperor for help in defending his Empire from the Muslim armies and not a war of aggression. It was the Muslims who were the aggressors during the crusades and both sides fought in terrible ways but the series of wars we know as the crusades were not started by Europeans but were started by the Muslim armies and were, from a European point of view, wars of defence and not of aggression.