after Charles II was restored to the throne in 1660. Again left to fall in ruin during the 18th century, many of the Device Forts were modernised and rearmed during the Napoleonic Wars, until peace was declared in 1815. Fears over a possible French invasion resurfaced several times in the 19th century, combined with rapid changes in technology, such as the development of steamships and shell guns in the 1840s, rifled cannon and iron-clad warships in the 1850s, and torpedo boats in the 1880s. This spurred fresh investment in those Device Forts still thought to be militarily valuable, and encouraged the decommissioning of others. By 1900, however, developments in guns and armour had made most of the Device Forts that remained in service simply too small to be practical in modern coastal defence. Despite being brought back into use during the First and Second World Wars, by the 1950s the fortifications were finally considered redundant and decommissioned for good. Coastal erosion over the centuries had taken its toll and some sites had been extensively damaged or completely destroyed. Many were restored, however, and opened to the public as tourist attractions. Early history and design Device programme Background The Device Forts emerged as a result of changes in English military architecture and foreign policy in the early 16th century. During the late medieval period, the English use of castles as military fortifications had declined in importance. The introduction of gunpowder in warfare had initially favoured the defender, but soon traditional stone walls could easily be destroyed by early artillery. The few new castles that were built during this time still incorporated the older features of gatehouses and crenellated walls, but intended them more as martial symbols than as practical military defences. Many older castles were simply abandoned or left to fall in disrepair. Although fortifications could still be valuable in times of war, they had played only a limited role during the Wars of the Roses and, when Henry VII invaded and seized the throne in 1485, he had not needed to besiege any castles or towns during the campaign. Henry rapidly consolidated his rule at home and had few reasons to fear an external invasion from the continent; he invested little in coastal defences over the course of his reign. Modest fortifications existed along the coasts, based around simple blockhouses and towers, primarily in the south-west and along the Sussex