Sandgate Castle was seized in 1642 by Parliamentary forces at the start of the first English Civil War between the supporters of King Charles I and Parliament, although its captain, Richard Hippesley, remained in post. The war ended in 1646 but, after the few years of unsteady peace, the Second Civil War broke out in 1648. The Parliamentary navy was based in Kent, protected by the other Henrician castles of Walmer, Deal and Sandown, but by May a Royalist insurrection was under way across the county, and the fleet joined the rebellion. Sandgate and its sister castles were occupied by the Royalists. Parliament defeated the wider insurgency at the Battle of Maidstone at the start of June, however, and then sent a force under the command of Colonel Rich to deal with the Kentish castles. Sandgate was still occupied by the Royalists that August, when Rich sent forces to prevent its garrison intervening to disrupt his assault on Deal and Sandown, but was recaptured soon after.