On the night before the Battle of Naseby, in June 1645, Ireton succeeded in surprising the Royalist army and captured many prisoners. The next day, on the suggestion of Cromwell, he was made commissary-general and appointed to the command of the left wing, with Cromwell himself commanding the right. The wing under Ireton was completely broken by the impetuous charge of Rupert, and Ireton was wounded and taken prisoner, but Cromwell charged and successfully routed the Royalists, freeing prisoners including Ireton.