Oliver Cromwell, the man who was a leading figure in passing the Self-Denying Ordinance Act, was named Lieutenant General of the Horse, which would become the most effective and elite group in the New Model Army. He had seen initial success as a cavalry commander during the early stages of the civil war, before the New Model Army came to be. The Parliamentarian defeat at Edge hill prompted him into creating what would become his own elite cavalry regiment. They coined the name "Ironsides" after the battle of Naseby where his men were given credit for attaining victory over the Royalists. The soldiers under his command all shared in Cromwell's strong Puritan beliefs, most fanatics being called zealots even by members of Parliament and other New Model Army commanders. Cromwell would eventually have numerous victories with his disciplined and loyal force all across England, Scotland, and Ireland. Once war was over, and the dust settled after he lead an execution of King Charles I, Cromwell would become Lord Protector of England and continue to use his Army to do his will.

Kishlansky, Mark. “The Case of the Army Truly Stated: The Creation of the New Model Army.” Past & Present, no. 81, 1978, pp. 51–74. JSTOR, www.jstor.org/stable/650363.

Plant, David. “Oliver Cromwell, 1599-1658.” Biography of Oliver Cromwell, 2012, bcw-project.org/biography/oliver-cromwell.