Christian Crusaders started with the Council of Clermont in 1095 AD. This is different from Augustine's "Just War" concept developed in 400 AD.

Your comment is an oversimplification of the historic complex interwoven developments. Mo slaughter his Semitic Jewish brethren after they took him earlier and tended to his wounds when he was in his ascendancy phase.

Mo's descendants further his unyielding philosophy when he passed. The critical difference between Christianity and Mo's version is the central emphasis on "forgiveness" central to Jesus's message.

As for the Jews, they do not believe Jesus is the messiah since he failed to fulfill four critical deeds. They are still waiting for their messiah.

Bottom line, the followers of the mythology of a superior deity has killed untold numbers of people.