… a series of military campaigns launched by the papacy between 1095 and 1291 against Muslim rulers for the recovery and defence of the Holy Land (Palestine), encouraged by promises of spiritual reward. At Wikipedia https://en.wikipedia.org/wiki/Crusades

Also the Crusading movement, theoretical, sociological, institutional, military, and financial dimensions of crusading. https://en.wikipedia.org/wiki/Crusading_movement

And Voltaire wrote of the “madness of the crusades”, driven by religious intolerance defined by misery and death.