 In 1643 he was appointed a colonel in the parliamentary army and in 1644 he was made High Sheriff of Cheshire, a post he held for four years.By early 1643 most of Brooke's immediate neighbours were powerful Royalists, in particular Sir John Savage, 2nd Earl Rivers of Rocksavage and Sir Thomas Aston of Aston.Further afield the Royalist leader of Lancashire was James Stanley, 7th Earl of Derby.