The son of a knight from Wiltshire, Ludlow studied at Trinity College, Oxford, and at the Inner Temple, London, and joined the Parliamentarian army at the outbreak of the Civil Wars. He fought against the Royalists in a number of campaigns before leaving the war to accept a seat in Parliament (1646). Ludlow helped the Independents (radical Puritans) expel the Presbyterians (moderate Puritans) from Parliament in 1648, and he was one of the judges who condemned King Charles I to death in January 1649. In the following month he joined the Council of State of the newly created Commonwealth. From November 1651 to October 1652 Ludlow was commander of the Cromwellian army that crushed Royalist resistance in Ireland and pursued the policy of transplantation of the Irish. After Cromwell made himself lord protector in 1653, Ludlow went into open opposition, claiming that Cromwell had betrayed republican principles; this resulted in his brief imprisonment at Beaumaris Castle. He played a leading role in the events that followed the end of the Protectorate, and upon the Restoration he escaped to Switzerland (August 1660). The memoirs Ludlow wrote while in exile were published six years after his death.