The title page of this film shows the shadow of a cross, with "No war is holy" written across the transept. Constantine’s Sword is the story of James P. Carroll's journey to uncover the roots of war. Carroll, a former Catholic priest whose father (Joseph Carroll) was a famous Air Force general, implies that there has been a relationship between religiously inspired violence and war, beginning with the adoption of Christianity by the Roman Emperor Constantine I in 312 AD. Constantine was convinced that he had won a battle because he had followed the instructions of a vision, to inscribe a sign of the cross (the Labarum) on the shields of his soldiers. In Carroll's view, this event marked the beginning of an unholy alliance between the military and the Church.