John spent much of 1205 securing England against a potential French invasion. As an emergency measure, John recreated a version of Henry II's Assize of Arms of 1181, with each shire creating a structure to mobilise local levies. When the threat of invasion faded, John formed a large military force in England intended for Poitou, and a large fleet with soldiers under his own command intended for Normandy. To achieve this, John reformed the English feudal contribution to his campaigns, creating a more flexible system under which only one knight in ten would actually be mobilised, but would be financially supported by the other nine; knights would serve for an indefinite period. John built up a strong team of engineers for siege warfare and a substantial force of professional crossbowmen. The king was supported by a team of leading barons with military expertise, including William Longespée, William the Marshal, Roger de Lacy and, until he fell from favour, the marcher lord William de Braose.