 Henry 's break with Rome incurred the threat of a large @-@ scale French or Spanish invasion . To guard against this , in 1538 , he began to build a chain of expensive , state @-@ of @-@ the @-@ art defences , along Britain 's southern and eastern coasts from Kent to Cornwall , largely built of material gained from the demolition of the monasteries . These were known as Henry VIII 's Device Forts . He also strengthened existing coastal defence fortresses such as Dover Castle and , at Dover , Moat Bulwark and <unk> Fort , which he personally visited for a few months to supervise . Wolsey had many years before conducted the censuses required for an overhaul of the system of militia , but no reform came of it . Under Cromwell , in 1538 – 9 , the shire musters were overhauled , but Cromwell 's work served most to demonstrate quite how inadequate they were in organisation . The building works , including that at Berwick , along with the reform of the militias and musters , were eventually finished under Queen Mary . 
