The philosophy of the crusades is summarized by Christopher Tyerman as follows:
"The crusades were wars justified by faith conducted against real or imagined enemies deﬁned by religious and political elites as perceived threats to the Christian faithful. The religious beliefs crucial to such warfare placed enormous significance on imagined awesome but reassuring supernatural forces of overwhelming power and proximity that were nevertheless expressed in hard concrete physical acts: prayer, penance, giving alms, attending church, pilgrimage, violence.
Crusading reflected a social mentality grounded in war as a central force of protection, arbitration, social discipline, political expression and material gain. The crusades confirmed a communal identity comprising aggression, paranoia, nostalgia, wishful thinking and invented history. Understood by participants at once as a statement of Christian charity, religious devotion and godly savagery, the ‘wars of the cross‘ helped fashion for adherents a shared sense of belonging to a Christian society, societas christiana, Christendom, and contributed to setting its human and geographic frontiers. In these ways, the crusades helped deﬁne the nature of Europe."
When I read this, I sense that the same may be true for all religiously inspired wars and conquests, such as the early islamic conquests. These began with the Islamic prophet Muhammad in the 7th century. He established a new unified polity in the Arabian Peninsula which saw a century of rapid expansion. The resulting empire stretched from the borders of China and the Indian subcontinent, across the Middle East, North Africa, Central Asia, the Caucasus, and parts of Europe (Sicily and the Iberian Peninsula to the Pyrenees).
Quote from Christopher Tyerman "God's War - a New History of the Crusades", 2006 The Belknap Press of Harvard University Press Cambridge, Massachusetts, added with information from Wikipedia. Illustration: Guy de Lusignan and Saladin in Battle / Mathew Paris, c.1250, source Wikiwand