Cromwell at the Battle of Marston Moor, 2 July 1644, (19th century). The Parliamentarians under Thomas Fairfax defeated the Royalists at this battle in Yorkshire. Cromwell (1599-1658) commanded the Parliamentarian cavalry that defeated the previously invincible Royalist cavalry of Prince Rupert. Marston Moor was a turning point in the English Civil War as it effectively lost the Royalists the north of England. Illustration from Harper's New Monthly Magazine.