His father's death meant Compton inherited his titles and regiments; he fought at the First Battle of Newbury in September 1643, then Cropredy Bridge in June 1644, before being routed by Oliver Cromwell at Islip, Oxfordshire in April 1645. He was present at Naseby in June, a defeat that destroyed the last major Royalist field army, and accompanied Charles on the attempt to link up with Montrose in Scotland that ended at Rowton Heath in September. He returned to Oxford and surrendered to the Committee of Both Kingdoms in February 1646, shortly before the war ended in June.