The Historia belli sacri (History of the Holy War) is a chronicle of the First Crusade written by an anonymous monk of the Abbey of Montecassino. It was composed some time after 1131, based in large part on the equally anonymous Gesta Francorum et aliorum Hierosolimitanorum and also incorporating fragments from the Historia Francorum qui ceperunt Iherusalem, the Gesta Tancredi and other unknown texts. Although heavily reliant on the Gesta Francorum, it is an important source for the Italo-Norman crusaders. Like the history of Robert the Monk and Guibert of Nogent's Dei gesta per Francos, both of which were used as sources by its anonymous author, the Historia belli sacri is "a serious and careful effort to rework the Gesta story and add to it significant information which is not found in a