Preston, Thomas (1585–1655), 1st Viscount Tara , soldier, was second son of Christopher, 4th Viscount Gormanston, and his second wife, Catherine, daughter of Sir Thomas Fitzwilliam of Baggotrath, Co. Dublin. Thomas attended the Irish college at Douai c.1600, before returning home to embark on a military career. In 1605 he received a commission as captain in the Irish regiment of Henry O'Neill, recruiting a company of infantry at his own expense. He arrived in Flanders at the end of the year, and served alongside Owen Roe O'Neill (qv), a nephew of Hugh O'Neill (qv), earl of Tyrone. A lifelong antagonism developed between the two men, partly as a result of the traditional animosity between the Old English of the Pale and the Ulster Irish, but principally personal in nature. According to the earl of Clarendon, the two young ambitious officers were in ‘perpetual jealousy of each other’ (quoted in G.E.C., Peerage, xii, 639). Preston saw action at the siege of Rheinburg in 1608, and continued to serve under Col. John O'Neill, Henry's successor as commander of the Irish regiment. In 1611 he supported Edward Fitzgerald for the position of sergeant-major, in an unsuccessful attempt to thwart Owen Roe's promotion. Preston also began to accumulate land and wealth in Flanders through his first wife (d. 1621), a daughter of Charles Van der Eycken of Brabant. Sometime before 1624 he married Marguerite of Namur, acquiring significant estates in the process.
Preston frequently returned to Ireland on recruiting missions for his regiment, where much of his authority arose from his close relationship with Hugh O'Donnell (d. 1642), 2nd earl of Tyrconnell, a leading Irish émigré. The Dublin administration consistently favoured Preston over O'Neill, hoping on one occasion to entice him back to serve in the Irish army. In 1634, the lord deputy, Thomas Wentworth (qv), considered Preston ‘one of the civilest gentlemen of his nation’ (Jennings, 574), and wrote a letter of recommendation to the Spanish on his behalf. The following year Preston became colonel of his own regiment, as did Owen Roe O'Neill – the fortunes of the two men seeming inexorably linked. He successfully defended Louvain in June 1635 against the combined forces of France and Holland, a feat that greatly enhanced his military reputation. Appointed governor of Genappe in Brabant, Preston surrendered the town to Frederick of Orange, commander of the Dutch forces (1641). Accusations of betrayal surfaced early in 1642, by which time a major rebellion had erupted throughout Ireland. His nephew, Nicholas Preston (qv), Viscount Gormanston, sent a messenger to Flanders, urging the colonel to assist the insurgents. Seizing the opportunity to escape a potential scandal over his conduct at Genappe, Preston received permission from the Spanish authorities to return home. Refusing to travel with Owen Roe, he landed at Wexford (Septembeer 1642), along with John Burke, a relative of Ulick Burke (qv), earl of Clanricarde, and a few veteran officers.
Preston immediately assumed command of the insurgents in Leinster and suffered a minor defeat in his first engagement with the royalist forces, at Timahoe (5 October). A few weeks later the first confederate general assembly in Kilkenny appointed him general of the Leinster army. Owen Roe served in a similar capacity in Ulster, while John Burke assumed temporary command in Connacht. Richard Bellings (qv), secretary of the executive supreme council, shrewdly observed how many of the confederate officers, including Preston, displayed ‘such a temper of abilities and parts as moved excellently by direction but irregularly when they were the balance upon which their own motion depended’ (Gilbert, Ir. confed., i, 74). An expert in the craft of siege warfare, a feature of the conflict in Flanders, Preston lacked confidence on the battlefield, a failing that would ultimately prove disastrous. On 20 January 1643 he captured Birr Castle, Co. Offaly, but two months later his army suffered its first defeat in an engagement with the royalist James Butler (qv), 12th earl of Ormond, at Ross, Co. Wexford. The following year, Preston's rivalry with Owen Roe forced the confederates to appoint a compromise candidate, James Tuchet (qv), earl of Castlehaven, to lead an army against the Scottish covenanters in Ulster. The campaign, plagued by poor leadership and internal divisions, proved a costly failure.
In early 1645 Preston besieged the strategic fortress of Duncannon, Co. Wexford, which fell to confederate forces (March) with negligible losses. Later that year, however, he quarrelled with Castlehaven during a joint campaign in Munster, thus preventing the confederates from seizing the few remaining enemy strongholds in the province. In 1646 Preston moved his forces into Connacht, supplied with arms and money from the newly arrived papal nuncio, GianBattista Rinuccini (qv). He captured the town of Roscommon, but failed to push on towards his ultimate objective, the port of Sligo. At the end of July, in the middle of this campaign, Ormond proclaimed the peace treaty agreed between the royalists and confederates four months earlier. Donough MacCarthy (qv), Viscount Muskerry, and the dominant peace faction supported the move, but the clergy, led by the nuncio, strenuously opposed the deal. This crisis presented Preston with an awkward dilemma. He had attended supreme council meetings from 1643 onwards, in an unofficial capacity, and clearly sympathised with the peace faction. None the less, his friend Nicholas French (qv), bishop of Ferns, urged him not to oppose the clergy on this issue. Plagued by doubts, the general declared for the peace at first, before changing his mind under the threat of clerical sanctions.
Preston joined the nuncio's newly formed supreme council, and assisted in the arrest of peace-faction leaders, including Muskerry and Bellings. Rinuccini ordered Owen Roe, another clerical supporter, to attack Dublin, but Bishop French insisted that Preston also be involved in the campaign. This dual command proved a fiasco, with both O'Neill and Preston more wary of each other than the enemy. Their combined force reached the outskirts of the city in early November, but O'Neill abandoned the idea of a siege after an English parliamentary squadron sailed into Dublin Bay. Preston meanwhile maintained a secret line of communication with the royalist leadership through Clanricarde. After O'Neill's departure, he offered his services to Ormond, provided he received sufficient guarantees on the matter of religion. He also requested that the lord lieutenant admit catholic troops into Dublin. Ormond stalled for time, but Preston eventually broke off the negotiations in the face of renewed threats of clerical sanctions, explaining to the royalists that his troops were not ‘excommunication proof’ (Lowe, Clanricarde letter-book, 343). At the subsequent general assembly in early 1647, the clergy laid charges of treason against the Leinster general, almost precipitating a confederate civil war, before Rinuccini intervened to calm the situation. On another front, resentment against O'Neill's forces increased throughout the Pale area, and Preston complained bitterly about the behaviour of the northern troops.
In an effort to divert internal confederate tensions, the supreme council ordered Preston to take the offensive in Leinster, and at the end of April his forces captured Carlow town, the sole surviving royalist stronghold in the south of the province. As he advanced towards Dublin, however, the general became embroiled in a royalist-sponsored plot to overturn the government in Kilkenny, and also explored the possibility of exporting his army abroad into French service in the event of failure. Desperate to prevent desertions, the supreme council sent Bishop French to urge Preston forward, arguing that everything would be ‘lost or won this summer’ (PRO, SPI 264/21. f. 35). After Ormond surrendered Dublin to the English parliament at the end of July, temporarily crushing royalist hopes in Ireland, Preston resolved to attack the forces of the new governor, Col. Michael Jones (qv). Having inexplicably failed to engage the enemy on more advantageous ground a few days earlier, Preston was forced into battle on 8 August at Dungan's Hill near Trim, Co. Meath. In one of the bloodiest battles in Irish history, Jones annihilated the best trained and supplied confederate army, although Preston and a number of his officers escaped. The anonymous author of the ‘Aphorismical discovery’ denounces Preston as ‘a foolish and treacherous knave’ (Gilbert, Contemp. hist., i, 129–31), but incompetence rather than treachery was the primary hallmark of his performance during this engagement. There is some evidence that Preston may also have suffered from a drink problem, as prior to the battle his doctor Owen O'Shiel (qv) had ordered the general to ‘abstain from all kinds of wine’ (CSPI, 1633–47, 489).
Temporarily appointed governor of Kilkenny and Waterford, the Leinster general tried to rebuild his shattered army. By November 1647 he had gathered together 4,000 men, for the most part raw recruits with no military experience. In 1648, when civil war erupted within confederate ranks, Preston joined forces with the peace faction in opposing the nuncio and Owen Roe O'Neill, although he carefully avoided engaging the Ulster army on the battlefield. Exasperated by the general's frequent switches of allegiance, Rinuccini denounced him as ‘a most unsteady man, unfit to take council with, and easily dictated to by the evil-minded’ (Aiazza, 375). In October 1648 Preston defeated a small force of Redshanks, assembled in Co. Wexford by Randal MacDonnell (qv), earl of Antrim, to oppose the peace negotiations with the royalists. On 28 December Ormond promised Preston a peerage in recognition of his support for the royalist cause, and he was created Viscount Tara by a patent dated 2 July 1650. Appointed governor of Waterford at this time, Preston surrendered the city on 10 August to the parliamentarians after a two-month blockade. He withdrew beyond the Shannon with the remnants of his forces in early 1651, erecting a fortress on the island of Inishbofin as a possible launching site for an invasion force from the Continent. None the less he opposed the various schemes for bringing troops over to Ireland, involving Charles, duke of Lorraine.
As the royalist position in Ireland collapsed, Preston proposed recruiting 5,000 men for service in Flanders, but even a reduced offer proved beyond the means of the Spanish exchequer. Appointed governor of Galway by Clanricarde, he sailed for the Continent shortly before its surrender (April 1652), and was subsequently exempted from pardon by the parliamentarians. After his arrival in Flanders he received the promise of a Spanish pension, although not on active service. When the money failed to materialise, Preston switched allegiance to France, but he failed to receive a military commission. He died in Paris on 21 October 1655. His eldest son Anthony, a former confederate officer, succeeded his father as viscount, but died four years later. In 1674 Sir Francis Blundell killed Anthony's son and heir, Thomas, but was subsequently acquitted of the charge of murder. As Thomas had no children, the peerage became extinct at this time. Preston's second son Sir James (known as ‘Don Diego’ by the Spanish) also played a prominent military role in Ireland during the 1640s.