Like his father and brother, Cromwell pursued a military career and rose to the rank of colonel of horse in the royalist army during the conflict in Ireland and England in the 1640s. He then served under the command of James Butler, then marquess of Ormond [I] (later duke of Ormond), against the Irish rebels and later the parliamentary army. In October 1666 Charles II officially reversed a declaration of treason issued by Parliament against him, Ormond and others.
Known by his civil war rank of colonel, by February 1661 Cromwell was captain of a troop of horse, serving in the regiment of George Monck, duke of Albemarle. When mutiny broke out in the garrison at Carrickfergus, co. Antrim, in 1666, Colonel Cromwell was sent for to help suppress it. By August 1670 he was listed as lieutenant-colonel of the regiment of Sir Arthur Forbes. In September 1672 he was attached to the regiment of Edward Conway, 3rd Viscount Conway. He continued to be listed as the commander of a troop of horse until the end of the reign.
Cromwell’s marriage in 1672 to Catherine Hamilton reinforced his connections to Ormond, whose sister, Mary Butler, was married to one of the Hamilton family. In November 1673, during the viceroyalty of Arthur Capell, earl of Essex, he was authorized to collect arms from the Catholics of co. Down.
After his succession in 1682 Cromwell was more generally known by his Irish rather than his English title. On 17 Apr. 1682 the king issued a warrant to Ormond to swear Ardglass as a member of the Irish privy council.
[his] heart is broke, and no man without concern (who has any good nature in him) can see so brave a man as he has shown himself to be in such a desponding condition as he is, and with good reason, for he is decrepit in body, disturbed in mind, and cannot get one able lawyer to plead for him.HMC Ormonde, n.s. vi, 483–4, 540; PRO NI, T.802 (2–6).
By March 1683 Ardglass intended to take his accusations to England and to use the English legal system. On 28 July he approached Arran for an extension of his leave from the army in order to attend the continuing chancery suit against Denny and Henry Muschamp.
In August 1683 Ardglass was made a deputy lieutenant of Staffordshire. Following his accession, James II reappointed him to the Irish privy council and in May he was again commissioned as a deputy lieutenant in Staffordshire. Also in May 1685 the lords justices were instructed to pay him an annuity of £400 p.a. on the Irish establishment.
In July 1685 Ormonde informed Archbishop Boyle that Ardglass had petitioned the privy council in England for the arrest of Muschamp until he had performed the chancery decree in his favour.
that the sending for a subject, out of this kingdom, upon a proceeding in chancery, in England, wherein both the parties, and the matter, … do all belong to this Kingdom, is without a precedent, and may be of sadder consequence to the … liberty of all the inhabitants … but especially of the Nobility, than can be easily foreseen.
Bodl. Carte 40, ff. 426–7.
Ardglass first attended the House of Lords on the opening day of James II’s Parliament, 19 May 1685. He was present on 29 days of the session before its adjournment on 2 July, and he attended the further adjournment of the House on 4 August. When the session resumed on 9 Nov. 1685, he was present on all 11 days before the prorogation of 20 November. In all he sat for just over 95 per cent of the session.
In January 1686 Ardglass was named to be colonel of a regiment of horse in the Irish army, made vacant by the promotion of James Butler, styled earl of Ossory [I], the future 2nd duke of Ormond, to the foot regiment which had belonged to Richard Butler, earl of Arran [I].
Ardglass’ attitude to James II’s policies is hard to establish. About May 1687 one commentator thought him a possible supporter; three other lists, including one probably drawn up after his death, indicated that he was opposed to the repeal of the Test Act. He continued to command his regiment of horse in Ireland until his death in 1687, surviving the reorganization of the Irish army by Richard Talbot, earl of Tyrconnell [I].
Ardglass died at Booncastle, co. Down, on 26 Nov. 1687 and was buried on 29 Dec. at the Abbey in Downpatrick. He died without male issue and the peerage became extinct, although his daughter, Elizabeth, was widely (if incorrectly) assumed to have become Baroness Cromwell.
