English longbow
Williams was recognised as an expert on military matters by his contemporaries, and wrote "A Brief Discourse of War, with his opinions concerning some part of Martial Discipline" (1590). He also wrote "Newes from Sir Roger Williams" (1591). After his death his account of his experiences in the Netherlands was published as "Actions of the Low Countries" in 1618. Williams gave detailed analyses of the different methods and effectiveness of the Dutch and Spanish forces in the Netherlands, commending the discipline of Parma's troops. He also examined methods of creating effective fortifications. Williams was a strong advocate of new weaponry, emphasising that the English army had to adapt to the new technology, as the traditional English longbow would soon be made obsolete by improved firearms. He argued that a combination of fireams and close-quarter deployment of pikes represented the future of warfare.