Which one was that? I guess you don’t mean the nadir of human conflict WWI and WW2 as they weren’t based in religious doctrine.

@Geoffrey51 100 years war for one crusades

@bobwjr The Hundred Years War was Plantagenet vs Valois. England vs France and totally regarding sovereignty

@Geoffrey51 wasn't sure of that one but the crusades was exclusively religious

@bobwjr Only partly. A dispute was regarding Jerusalem but also papal sovereignty between the Catholic Church and The Holy Roman Empire and the power of aristocratic families in Europe.

Remember there were five patriarchate at this time of Rome, Jerusalem, Alexandria, Constantinople and Antioch with the Bishop of Rome being ‘first among equals’. This in itself was.dynastic rather than religious conflict although it was sold on religious grounds as death in a holy war was a form of martyrdom.

There is suggestion that the First Crusade was to engage the restless young nobles of Europe who were causing mayhem at home with a focus which resulted in the marauding, pillaging and atrocities throughout their route to Jerusalem. See Stephen Runciman’s work ‘A History of The Crusades’ (3 vols 1951-54)