Maryland'deki Loyola Koleji'nde tarih profesörüdür. Aralarında Medieval Military Technology, Infantry Warfare in the Early Fourteenth Century, Joan of Arc: A Military Leader ve Guns and Men in Medieval Europe'un da olduğu pek çok kitabın yazarıdır.
By the flash and combustion of fires, and by the horror of sounds, wonders can be wrought, and at any distance that we wish–so that a man can hardly protect himself or endure it.