How the crusades fits in the gospel of Christ?
Not a quick and easy answer. Here’s a decent article on the crusades. It’s a bit of a read, but worth it in order to understand what was being accomplished, and the importance of protecting Christendom, (a concept just barely even understood anymore). Anyway, there were many actions taken during the crusades which were not fitting of the Church. Those actions were apologized for by the Church during the reign of Saint John Paul II. This isn’t completely dismissive of the crusades though, which to my reading were still somewhat necessary. Just not conducted perfectly. In the end, it was love of Christ and neighbor which drove the crusaders. But alas, man is a fallen creature. Men will be men. There is not much more the Church can do, but apologize for whatever acts were done by individuals and groups during the crusades which fell outside of the loving heart of the mission. This has been done.
In what sense were the crusades “necessary”, since they failed, and yet the Church went on?
We must look at the big picture, both geographically and chronologically. The distilled essence is that if not for the Crusades, the battle of Lepanto, the expulsion of the Moors from Spain and a few other actions, we very likely would be bowing toward Mecca five times per day. Oh, Islam is still trying to conquer the world, but in the legal realm rather than militarily.
Yes, well it was necessary in the sense that Christendom was under violent attack and invasion from the Muslims; I don’t believe the correct action is to ignore the pleas of our friends in Constantinople and let them be overrun. In addition, despite it being a failure overall, it certainly was necessary to protect Christendom in the Middle East, as we can see by looking around the world nowadays and realizing that Christianity has been and is being wiped out in these countries. It certainly was necessary to try to save the numberless souls who were lost over the centuries to Islam. If the Crusades were an overall success, these countries would all be Christian at the moment.
The crusades are related to the gospel of Christ through the Christian teaching on warfare.
The Christian just war doctrine only permits wars if four conditions are met: [LIST=1]
*]The war must be waged by a legitimate authority
*]The war must have a reasonable and morally acceptable cause
*]The war must be necessary, that is, there must be no other way of achieving the legitimate objective
*]The war must be fought by acceptable means
[/LIST] The second condition forbids wars of aggression because those do not come from an outside cause. Thus the Church’s tradition has only accepted wars of defense – either of your own nation or of a persecuted people who are asking for help.
The first crusade was called for the defense of persecuted Christians and Jews in the Holy Land. The people behind it tried their best to follow the four conditions outlined in the Church’s just war tradition. This is one reason why many Catholics argue that the crusades were justified. But we have to remember that seven crusades were called for the liberation of the Holy Land, not just one, and a crusade was called against the Albigensians, and crusades were called by some European monarchs rather than by the pope, and crusades were called against some European monarchs because they acted against the pope. Each crusade needs to be judged individually.
For an overview of the original seven crusades, I hope you’ll read the article “The Real History Of The Crusades” by Thomas Madden, available here: catholicculture.org/culture/library/view.cfm?id=4461&repos=1&subrepos=0&searchid=1342617
And, if you want to do further research, look up the characters and major events of the Crusades as they are listed here: catholicculture.org/culture/library/view.cfm?id=10014&repos=1&subrepos=0&searchid=1342617
In my humble opinion without the Crusade, the Holy places in the Holy Land would have been not more than ruins.
Please check this link. I am not a historian and I cannot confirm the accuracy of every piece of information presented, but it may shed some light on this subject from a historical perspective.