MacCarthy, Justin (c.1643–1694), Viscount Mountcashel and Baron Castleinch , army officer, was born probably in Blarney, youngest of three sons of Donough MacCarthy (qv), Viscount Muskerry and Earl Clancarty, and his wife Eleanor, sister of James Butler (qv), marquess of Ormond and lord lieutenant. Muskerry was a leading Ormondist confederate; his extensive estates were confiscated and his family sought refuge in France, where Justin was brought up. Though the estates were recovered with the restoration, Justin as the youngest son was not a main beneficiary of the inheritance and followed soldiering as a professional career. He secured his first military experience in an Irish regiment in the French service in Louis XIV's Dutch war (1672–8). He was already well known in France by 1676 when he was appointed to command a regiment of foot of which the duke of Monmouth was colonel-proprietor. The regiment, which fought in the Netherlands for the next two years, was mainly an Irish corps, in which a number of the officers were MacCarthys and in which Patrick Sarsfield (qv) held a commission. The friendship of the two soldiers was to grow in later years.
Justin MacCarthy's career was in the doldrums at the time of the ‘popish plot’ (1678–81) but flourished from the accession of James II (qv) (February 1685). He strongly supported the catholic new deal of Richard Talbot (qv), earl of Tyrconnell, and took a leading part in catholicising the army. He was appointed to the rank of general with appropriately generous remuneration, and also became a member of the Irish privy council. At the outset of the revolution of 1688, he dealt expeditiously with incipient Williamite rebellion in Munster, prevented Bandon from becoming another Derry, and in general ensured that the province was made safe for James, whom he welcomed on the deposed monarch's arrival at Kinsale (March 1689). In May 1689 he was made master-general of the artillery because of his expertise in the area of arms. In the Jacobite parliament of 1689 he represented Co. Cork in the commons, and brought up from the commons to the lords the bill for the repeal of the act of settlement (1662). Shortly afterwards he was created Viscount Mountcashel and Baron of Castleinch, but was too busy with military matters to spend much time in the house of lords.
Mountcashel disliked and disagreed with James's English advisers and was more concerned with the poor prospects of Irish resistance to William III (qv) than with any sense of loyalty to James. While Derry was under siege, the Jacobites under Mountcashel's leadership attempted to capture Enniskillen. The Enniskilleners, however, went on the offensive and inflicted a devastating defeat on the Jacobites at the battle of Newtownbutler (10 August 1689). Despite a display of personal bravery, Mountcashel was severely wounded and taken prisoner, while his regiment was annihilated. Together with the lifting of the siege of Derry, Newtownbutler was a disaster for Jacobite morale and was seen by contemporaries as a turning-point in the northern war.
After some months recovering from his wounds, Mountcashel escaped from Enniskillen at the end of December 1689 in controversial circumstances, his captors asserting that he had broken his parole. He was given a hero's welcome in Dublin, where he was received at the castle by King James and almost immediately became involved in the formation of the first Irish brigade for the French service. It had long been accepted that the Jacobites needed a trained French corps if they were to have any hope of gaining the upper hand against their Williamite enemies. Louis XIV's wars had taken a heavy toll of French manpower, and he and his war minister Louvois were insistent that the expedition of a corps to Ireland would have to be made good by the sending over of Irish recruits to France. This exchange of troops was the background to the formation of the first large unit to fight under the French flag, though many Irishmen had previously pursued military careers on the Continent.
Mountcashel had long been mentioned for the command of such a brigade, being judged by the French – and in particular by the comte d'Avaux (qv), Louis XIV's envoy to James – as the ideal commander to keep the Irish troops faithful and disciplined in the French service. Apart from his personal and professional qualities, he was devoted to France, was known and esteemed there, and was well acquainted with French military discipline. His aristocratic lineage also weighed with d'Avaux, who commented that Sarsfield was ‘not a man of noble birth like MacCarthy’. Mountcashel, in turn, had set his heart on the command of the brigade: ‘the thing I most desire in the world . . . if they should send another, that would cause me the greatest grief and I would only think of retiring for the rest of my days’. His ambition transcended any commitment he may have felt to continue serving the Jacobite cause at home.
A formal contract of service was entered into by the Irish troops. Originally, the brigade of which Mountcashel was commander-in-chief comprised five regiments, but after reshuffling in France and before it had seen any active service it was reorganised into three – Mountcashel's, Daniel O'Brien's, and Arthur Dillon's (qv), each regiment consisting of sixteen companies of a hundred men each, excluding officers, in all amounting to some 5,000 men.
On 18 April 1690 the men of Mountcashel's brigade left for France from Cork harbour, sailing in the same vessels that had brought a French corps under the comte de Lauzun (qv). The Irishmen ‘were shipped off with a great deal of howling’ (Colles diary, Ormonde MSS, new ser., viii, 378). Ragged, unarmed, inexperienced, this force was the vanguard of the Wild Geese; within a year, many of its members were to shed their blood, the first of great hosts of Irishmen who were to die under the French flag. On arrival in France, the Irish were drilled, clothed, armed, and generally transformed by French military efficiency into a smart and impressive body. Their special uniform was a grey coat or tunic and they wore a felt hat with one side turned up, to which was pinned the white cockade of the Bourbons. Their flag was St George's cross with the lion and crown.
Mountcashel, now a well paid lieutenant-general of France, led his men through central France in the late summer of 1690 to serve under the marquis of St Ruth (qv) in Savoy, where the brigade won its first laurels. A large share of the credit for the conquest of Savoy lay with the Irish, and St Ruth asserted they had ‘done marvels’; but they also suffered considerable casualties. Mountcashel's men also distinguished themselves in the 1691 Catalonian campaign. The French commander, the duc de Noailles, who praised the Irishmen highly, noted they were generally in good spirits and always first into the breach.
With the arrival on the Continent in the winter of 1691–2 of the 14,000 officers and men who entered the French service after the treaty of Limerick, the story of Mountcashel's brigade merges with the wider history of the Wild Geese. But the introductory period – the campaigns of Mountcashel's men in Savoy and Catalonia in 1690–91 – was of great significance. It proved the wisdom of Louvois and d'Avaux in foreseeing that the Irish troops, with proper training and equipment, would make excellent soldiers. It also vindicated the choice of Mountcashel as commander. Moreover, the brigade's exploits convinced the French war office that the Irish would be invaluable in larger numbers. Mountcashel himself had been largely responsible for the success of the experiment.
Politically, Mountcashel gave his full support to those Jacobites in Ireland who were determined to prosecute the war against the Williamites to the bitter end. What might be called the war party was led by Sarsfield, while Tyrconnell favoured a compromise settlement with William. Mountcashel readily responded to Sarsfield's entreaties that he should promote the war party's interests at Saint-Germain and Versailles. Indeed, later in 1691 he was still maintaining that the situation in Ireland was far from hopeless and that speedy French assistance could yet turn the scales. He strongly protested against James's 1693 announcement (in a futile and obvious bid to win some protestant support for his lost cause) that he would consent to uphold the act of settlement in Ireland. James's subsequent attempt to placate him indicates his awareness of Mountcashel's influence with the Irish in France. Mountcashel's own estates in Ireland, in the Ovens district of mid-Cork, were confiscated by Williamite attainder.
Mountcashel's regiment saw further service on the Rhineland front in the spring of 1693. The following year, the wounds he had received in several engagements began to trouble him again. He sought relief at the curative waters of Barèges in the central Pyrenees but died there on 1 July 1694. He had wished to be buried in Ireland but this proved impossible at the time, and he was interred at Barèges. He married Arabella, daughter of Thomas Wentworth (qv), earl of Strafford; they had no children.
Justin MacCarthy combined remarkable physical bravery with a strong moral courage and independence. He was capable of a large tolerance, unusual at the period and greatly appreciated by those who differed from him in religion. As a military commander, perhaps his greatest asset was that he knew how to hold the balance between discipline and popularity – a popularity largely based on his constant concern for the welfare of his troops. His life and career are historically significant in a number of respects. He evokes the romantic aura of an age when a high value was set on the achievement of military glory. A study of his life illuminates Irish history at a point of close contact with the France of Louis XIV. Moreover, his kind of Jacobitism reflected the particular concerns of the native Irish aristocracy in its last days. Culturally, he belonged to three worlds – France, England, and Gaelic Ireland. Justin MacCarthy was also Saorbhreathach Mac Cárthaigh who commissioned a genealogy of his family in the Irish language and whom Gaelic poets praised and lamented. Finally, he is both the pioneer and prototype of the Wild Geese, the embodiment of that élan and valour which Irish tradition deemed to be the distinctive marks of the soldiers of the Irish Brigade.