Bagenal, Walter (1614–52), soldier and politician, was eldest son of George Bagenal of Dunleckney, Co. Carlow, and Joan, daughter of Walter Butler (qv), 11th earl of Ormond. The Bagenals originated from Staffordshire in England and only arrived in Ireland during the sixteenth century. In 1585 Dudley Bagenal (Walter's grandfather) purchased the vast Carew estate, and after losing the hereditary governorship of Leighlin castle George Bagenal, MP for Co. Carlow in the 1613 parliament, built a new residence nearby at Dunleckney. At the death of his father (1625), Walter became a ward of court; although little is known of his education, he was a fluent Irish-speaker, and appears to have remained a catholic. In 1632 he married an Englishwoman, Elizabeth, daughter of Christopher Roper, 3rd Lord Teynham, and widow of John Plunkett of Dunsoghly, Co. Dublin. At the outbreak of the rebellion in October 1641 the lords justices in Dublin appointed Bagenal as the governor of Co. Carlow. A short time later Sir Thomas Butler, his local rival, received the same commission, and when troops from Dublin took control of Carlow castle from Bagenal he decided to switch sides. He is also accredited with persuading Richard Butler (qv), 3rd Viscount Mountgarret, to join the rebels. In alliance with Sir Morgan Kavanagh, Bagenal seized the old family home, and distinguished himself at the battle of Kilrush (April 1642), where his leadership at a critical moment saved the rebel army from total destruction. Bagenal attended the first confederate general assembly in Kilkenny (October 1642) and was elected to the Leinster provincial council.
A leading member of the peace faction, he supported the 1643 cessation with the royalists, and for the next three years commanded the crucial garrison at Leighlinbridge on the Barrow river. After the rejection of the first Ormond peace treaty in September 1646, he assisted his cousin, the lord lieutenant, James Butler (qv), marquess of Ormond, to cross the Barrow with his troops and return to Dublin, thus preventing his capture by Owen Roe O'Neill (qv). For this reason the papal nuncio, GianBattista Rinuccini (qv), had Bagenal arrested along with the other principal supporters of the treaty. Released after a few months, Bagenal rejoined the Leinster confederate army and intrigued with its general, Thomas Preston (qv), in attempting to reach a fresh accommodation with Ormond. He attended the general assembly in January 1647 and made an impassioned speech in favour of the peace treaty, but to no avail. In October 1647 Sir Maurice Eustace (qv) listed Bagenal among those confederates anxious to submit to royal authority. Elected as a supernumerary member of the supreme council at the subsequent general assembly (December 1647), he supported the nuncio's enemies in the confederate civil war that erupted shortly afterwards, fighting against O'Neill's Ulster army till 1649 and then against the Cromwellians. In 1651 the royalist lord deputy, Ulick Burke (qv), marquis of Clanricarde, appointed him as one of the commissioners for the province of Leinster, with full civil and military powers. On 12 May 1652 he signed the articles of Kilkenny with the forces of the English parliament, an agreement that brought the war in Leinster to an end. Bagenal acted as one of the hostages for the performance of the articles, but the governor of Kilkenny, Col. Daniel Axtell (qv), brought him to trial, charged with the hanging of an Englishman, William Stone, in May 1642. Found guilty of murder by the high court of justice, he was executed by firing squad in October 1652. His eldest son George had been killed during a skirmish in 1651, but Charles II ordered the restoration of Dudley Bagenal (qv), the eldest surviving son, to the family estate in 1665. Dudley later supported James II, and sat as MP for Co. Carlow in the 1689 parliament.