Query: How many knights out of ten would be mobilised?
Context: 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.