an army started by Oliver Cromwell during the English Civil War in 1645, which was well-trained and skilled at fighting. It consisted of Roundheads, fighting against King Charles I and his Cavaliers. (1645) Army that won the English Civil Wars for Parliament. It was formed to provide a well-trained force drawn from all parts of England instead of the limited local militias. The new army also replaced the private armies raised by individual generals that lacked a unified command. Under Baron Fairfax and Oliver Cromwell, the New Model Army won the Battle of Naseby and effectively ended the first phase of the Civil Wars