The Parliamentarians, also known as the Roundheads for their close-cropped hair, were the forces loyal to the parliament of England during the English Civil War from 1642 to 1652. The Parliamentarians dominated the south and east, as well as the urban centers, and they sought to decentralize the government and have more of a say in the government. The Parliamentarian cause was led by Thomas Fairfax and Oliver Cromwell during its early years, and it would win the civil wars due to the "New Model Army" reforms. In 1660, the Cavaliers ("royalists") of Charles II of England would return to England and overthrow Parliament, and Parliament was overthrown.
The Parliamentarians found most of their support in the industrial cities, ports, the cathedral cities (apart from York, Chester, and Worcester), and the economically advanced south and east of England. They found their strongest backing among the urban middle classes, Puritans, merchants, lawyers, and yeoman farmers. Their heartlands were in the more industrialized and commercially-oriented regions of eastern and northern England, such as East Anglia, the Midlands, Yorkshire, Lancashire, and the Home Counties around London. The Roundheads embodied the rising commercial and religious dissenting interests. The Parliamentarians initially supported constitutional monarchy, but Oliver Cromwell reinvented the ideology as a republican one, leading to the formation of the Commonwealth of England. In the post-Civil War era, many former Roundheads formed the constitutionalist Whigs.