Rushworth followed the lead of John Pym, who, in a speech in the House of Commons on 17 April 1640, attacked the King and his government for problems within the country. After the outbreak of the Civil War, Rushworth as an "embedded journalist" followed the battles of Edge Hill (1642), Newbury (1643 and 1644), Marston Moor (1644) and Naseby (1645). In 1645 he became secretary to Thomas Fairfax, commander-in-chief of the New Model Army. When Charles I was captured, Rushworth began to record details of events leading up to, during and following the trial and execution of the King. He reported the Battle of Preston (1648) and the Battle of Worcester (1651).