Deal Castle was seized by Parliamentary forces at the start of the first English Civil War between the supporters of King Charles I and Parliament, resulting in the dismissal of Byng as a suspected Royalist and his replacement by Colonel Rainsborough, a vice-admiral. The castle did not play a significant role in the remainder of the initial conflict. After the few years of unsteady peace after 1645, the Second Civil War broke out in 1648, this time with Charles' Royalist supporters joined by their Scottish allies. The Parliamentary navy was based in the Downs, protected by Walmer and the other Henrician castles, but by May a Royalist insurrection was under way across Kent.