of the first campaign he returned to his native county, and became captain of a troop of horse for Sir Edward Hungerford's regiment (10 April 1643). When Hungerford took Wardour Castle, Wiltshire (8 May 1643), he appointed Ludlow its governor. Ludlow made himself famous by the tenacity with which he endured a three months' siege. His answer to the summons sent him by Sir Francis Dodington was published by the newspapers of both parties—by ‘Mercurius Aulicus’ to show his obstinacy, by ‘Mercurius Britannicus’ to show his fidelity (Mercurius Aulicus, 19 March 1643; original Tanner MSS. lxii. f. 627).
After a short imprisonment at Oxford, Ludlow was exchanged early in the summer of 1644, and became major of Sir Arthur Hesilrige's regiment of horse, in the army under Sir William Waller (10 May 1644). On 30 July 1644, however, Waller gave him a colonel's commission, and sent him into Wiltshire to raise a regiment of horse. Parliament about the same time made Ludlow sheriff of his native county, and for the rest of the war he was engaged in endeavouring to reduce it to obedience. He took part, however, in the second battle of Newbury (27 Oct. 1644), in the siege of Basing House (November 1644), and in an expedition for the relief of Taunton (December 1644). At the beginning of January 1645 his regiment was surprised by Sir Marmaduke Langdale [q. v.] at Salisbury, and Ludlow himself escaped with great difficulty. On the formation of the new model, the committee for the selection of officers, ardently backed by Sir Arthur Heselrige, recommended Ludlow for the command of a regiment, but the Wiltshire committee professed that they could not spare him (Memoirs, i. 113, 127, 141; Nichols, Leicestershire, ii. 744).
Ludlow's election as member for Wiltshire (12 May 1646) shows the esteem which his countrymen had for his services. Like his father, he from the first associated himself in parliament with the most advanced section of the popular party, with Harry Marten and the so-called ‘commonwealthsmen.’ Without being exactly a leveller or an anabaptist himself, he sympathised strongly with both parties, and was trusted by them. As a speaker he did not distinguish himself, and his later political importance was due to his influence outside parliament rather than within it.
Ludlow took the part of the army in their quarrel with the parliament in the summer of 1647, and signed the engagement of 4 Aug. (Rushworth, vii. 755). But the negotiations of the army leaders with the king, and their suppression of the levelling party in the army, roused his suspicions. He opposed the vote of thanks given to Cromwell for his conduct at the Ware rendezvous, and was still further alienated from him by his avowed preference for monarchy (Memoirs, i. 207, 223, 240). Nevertheless in the summer of 1648, when Major Huntington accused Cromwell, Ludlow wrote to encourage the latter, and to promise him support (ib. i. 253, 258). Convinced of the danger of a treaty with the king, he urged Ireton and Fairfax to put an end to the proposed negotiation by force, and was one of the chief promoters of Pride's Purge in December 1648 (ib. pp. 263, 267; Gardiner, Great Civil War, iii. 471, 537). He was appointed one of the king's judges, was present at eleven meetings of the court, and his name is the fortieth in the list of those who signed the king's death-warrant (Nalson, Trial of Charles I). On 7 Feb. 1649 he was ordered to draw up instructions for the proposed council of state, was himself elected a member of that body on 14 Feb., and was also a member of the second council elected in February 1650 (Commons' Journals).
When Cromwell returned from Ireland in June 1650, he thought it necessary to appoint ‘some person of reputation and known fidelity’ to act as second in command to Ireton, and to replace him in case of death or illness. For this post he selected Ludlow, to whom he privately vindicated his former conduct, and professed his desire to effect that ‘thorough reformation of the clergy and the law’ on which Ludlow had set his heart. Ludlow hesitated to accept, pleading the condition of his estate, but was nominated by the council of state on 27 June, and approved by parliament on 2 July following (Memoirs, i. 321–33; Commons' Journals, vi. 435). He received a commission from Cromwell as lieutenant-general of the horse in Ireland, and from parliament as one of the commissioners for the civil government of that country. In the latter capacity he was paid a salary of 1,000l. a year (the instructions of the commissioners are printed, ib. vi. 479, vii. 167). Ludlow, however, complains that during the four years he served in Ireland he expended 4,500l. out of his own estate over and above his pay (Memoirs, i. 465). He landed in Ireland in January 1651, passed the Shannon with Ireton in June, and took part in the siege of Limerick. On the death of Ireton (26 Nov. 1651), the commissioners of the parliament issued a circular letter ordering the army to give obedience to Ludlow, but on 9 July 1652 parliament voted Fleetwood commander-in-