Waller, Sir Hardress (1604–66), soldier, politician, and regicide, was the son and heir of George Waller of Groombridge, Kent, England, and his wife Mary, daughter of Richard Hardress. Waller's family was one of the wealthiest in Kent, and his cousin was the parliamentarian general Sir William Waller, yet his career was dominated by his Irish connections, acquired when he married (1629) Elizabeth, daughter and coheir of Sir John Dowdall of Kilfinny, Co. Limerick. He was knighted in the same year. Soon afterwards, Waller moved to his new estates in Ireland, centred on Castletown, Co. Limerick, and became closely involved in Munster affairs, sitting as MP for Askeaton in the Irish parliaments of 1634 and 1640, and enjoying the patronage of the 1st earl of Cork (qv) and (especially) Sir William St Leger (qv), whom Waller would later describe as ‘so dear a friend and, I may say, a father’ (Bodl., MS Carte 3, f. 498). During the 1640 parliament Waller became known as an opponent of the earl of Strafford (qv), and worked closely with the catholic Old English in petitioning against the government and (in April 1641) negotiating with the crown to lift the threat of further plantation in northern Munster and Connacht.
Waller's attachment to the Old English did not survive the outbreak of the Irish rebellion in October 1641. Under St Leger's command, Waller was made governor of Askeaton castle and a member of the Munster council. When the Munster protestants began feuding among themselves in 1642, Waller sided with St Leger and his son-in-law, Lord Inchiquin (qv), against the Boyle faction, and on St Leger's death he took command of his regiment. In September 1642 Inchiquin sent Waller to England to gain support for the Munster war effort, with little result. During the summer of 1643 Waller became increasingly critical of the king, and on his return to Ireland in the autumn he openly opposed the cessation of arms signed with the confederates. In the spring of 1644 Waller was outspoken in his attacks on the confederates, but he retained Inchiquin's favour and was made governor of Cork city. In May 1644 Waller again travelled to Oxford as Inchiquin's agent, but when his commander defected to parliament in July, he quickly moved to London.
While in England, Waller's career took a very different turn. In the spring of 1645 he was serving in the parliamentarian army, possibly under his cousin, Sir William Waller, in the west. By April he had taken the solemn league and covenant, and was then appointed as a colonel in the recently formed New Model Army. He led his regiment at the battle of Naseby in June, and was wounded at the siege of Basing House in October. By the end of the year, Waller seems to have had a conversion experience. His letters suddenly became full of religious language, and instead of supporting Inchiquin as a possible lord lieutenant of Ireland, he now championed Oliver Cromwell (qv), ‘whose spirit moves much that way’ (HMC, Egmont MSS, i, 264–5). For the next few months, Waller was in the south-west of England, where he commanded the forces besieging Exeter, but he continued to push for a swift reconquest of Ireland, and was critical of the ineffectual new lord lieutenant, Viscount Lisle (qv). When, by December 1646, no relief had been sent to Munster, he joined other Irish Independents at Westminster in calling for the immediate dispatch of Lisle's troops to Ireland. When Lisle eventually sailed, Waller accompanied him as major-general, but when Lisle's commission came to an end in April, Waller was sent home again, as Inchiquin angrily refused to employ him any longer.
In England in the summer of 1647, Waller became involved in the politics of the New Model Army, taking part in the army's debates and negotiating with the army's agitators. In October he was present at the Putney debates, and called for the army to take direct action against parliament, if their ‘rights’ could not be satisfied otherwise. Fairfax clearly thought much of Waller, whom he appointed commander of all the forces in Devon and Cornwall in the new year of 1648. He was stationed there during the second civil war, and moved against known royalists swiftly and brutally, before leading the assault on the rebels who held out on the Scilly Isles. In early December Waller was back in London, where he was one of the committee that organised Pride's purge. When the purge took place, on 6 December, Waller joined Thomas Pride and other officers in threatening, and in some cases assaulting, the presbyterian MPs who tried to take their seats. In January 1649 Waller was chosen as a commissioner for the high court of justice to try the king himself. He attended the trial proceedings as many times as Cromwell, and, on 29 January, signed the king's death warrant – the only Irish protestant to do so.
With the revolution completed in England, Waller turned his attentions back to Ireland, and he was an important adviser to Cromwell in the weeks before the army set sail for Dublin in August 1649. Yet Waller's regiment was not chosen to go to Ireland, and for the next six months he was back in the south-west, guarding against unrest in Devon and Cornwall. At the end of November, however, he was given command of a newly recruited regiment bound for Ireland, and by the end of the year he had crossed to Munster. Waller was promoted to major-general in June 1650, serving in the midlands and conducting the siege of Limerick from September of that year. When Limerick fell in June 1651, Waller was appointed governor, but resigned in favour of his son-in-law, Col. Henry Ingoldsby (qv), in order to ravage first Co. Clare, then Co. Kerry. Once the fighting was over, Waller resumed his role as a military politician, attending parliament in the winter of 1652–3 with the army's grievances. He returned to Ireland in May 1653, confident that he now had ‘a great interest in the soldiery’ (HMC rep. 5, 193). Waller's hopes of a political career were not fulfilled, however. Although he was elected for Co. Kerry, Co. Limerick, and Co. Clare in the union parliaments of 1654 and 1656, on both occasions he was ordered to remain with his command in the south-west of Ireland.
During the 1650s Waller drew closer to the protestant community in Munster. In October 1653 his daughter Elizabeth married Maurice Fenton of Mitchelstown, and at about the same time his son James married the daughter of Col. Randall Clayton of Mallow. By 1656 Waller was on good terms with the Boyle family, including Lord Broghill (qv), and with Broghill's friend Henry Cromwell (qv), who repeatedly recommended Waller to the government at Whitehall. Such high-level support was important for Waller, who fought a constant battle to secure the repayment of his military arrears through land grants. Waller's claims were eventually settled by the union parliament in May 1657, but it was too late. In 1658 Henry Cromwell warned his father that Waller ‘thinks himself forgotten’ and had become ‘somewhat melancholy’ (Thurloe state papers, ed. Birch, vi, 734, 773–4), and recommended that he receive some honour. With Oliver's death, Henry was even more worried, and classed Waller among the untrustworthy officers. Although once again elected for parliament in 1659, Waller did not sit. After the collapse of the protectorate in May, Waller announced his support for the ‘good old cause’, arrested Henry Cromwell at Phoenix Park, and was allowed to retain his command under the new commonwealth.
During the winter of 1659–60, Waller's actions became erratic. In November 1659 he supported John Lambert's military government in England, yet in December he joined the Irish protestant officers' coup in favour of the restored Rump. The arrival of Gen. George Monck (qv) in London, and the return of the MPs secluded at Pride's purge, was the last straw. As a leading figure in the purge, and a regicide, Waller panicked. Seizing Dublin castle on 16 February 1660 with a small group of allies, he tried to mount a further coup, but was soon forced to surrender. Sir William Waller managed to persuade the council of state to release him, and in May 1660 he fled to France. Later in the year he returned to England, and took advantage of Charles II's proclamation promising leniency to regicides who ‘rendered’ themselves. After a trial in which he acquired an unenviable reputation as ‘one who would say anything to save his life’ (Ludlow, A voyce from the watch tower, ed. Worden (1978), 209), Waller was convicted, but his death sentence was commuted to life imprisonment, and he was sent to Mont Orgueil castle on Jersey, where he died in 1666. Waller was survived by his second son, James, his eldest son, Walter, having died in the later 1650s.