Sir John William O'Sullivan (c. 1700 – c. 1760) was an Irish professional soldier, who spent most of his career in the service of France, but is best known for his involvement in the Jacobite rising of 1745, an attempt to regain the British throne for the exiled House of Stuart. During the Rising, he acted as adjutant general and quartermaster general of the Jacobite army and had a major influence on the campaign.
Although many secondary works give his surname as "O'Sullivan", he used the form "Sullivan" in his own correspondence.
Early career
O'Sullivan was born 1700 at Cappanacush near Kenmare in County Kerry, one of two sons of Dermot O'Sullivan, whose family estate of Dunkerron had been confiscated under the Act for the Settlement of Ireland 1652.
Information on his early life is limited and taken from The Young Juba, an often unreliable biography of Charles Stuart written in 1748 by Aeneas MacDonald, using the pseudonym Michell.
The Penal Laws limited opportunities for the Irish Catholic gentry and like many contemporaries, O'Sullivan was educated in Paris and Rome, possibly in preparation for the priesthood. MacDonald suggests he became tutor to the son of the Marquis de Maillebois, and accompanied him in the 1739 French and Genoese reconquest of Corsica. He is recorded as serving in Italy and on the Rhine during the War of the Austrian Succession, although few details are provided.
1745 rebellion
Following the abandonment of a French invasion attempt in early 1744, the Stuart heir Charles began planning a small-scale landing in Scotland to take place the following year. He started purchasing weapons in early 1745 while the French provided limited logistical support, much of it brokered by Lord Clare; O'Sullivan joined Charles's household in March.
Charles's former tutor Sheridan claimed to have first recommended him, though he is also suggested to have been recruited directly by Clare. A contemporary account said that "no one who knows Mr. Sullivan can deny his being one of the best bred, genteelist, complaisant, engaging officers in all the French troops". Charles enjoyed O'Sullivan's company and trusted his advice: in return, O’Sullivan was to be unerringly loyal to him. From this point he was closely involved in planning the 1745 expedition and as one of the "Seven Men of Moidart" accompanied Charles during his landing on Eriskay.
The campaign got off to a poor start when the ship Elizabeth, carrying weapons and a force of Franco-Irish regulars, had to turn back after being intercepted and damaged by HMS Lion. On arrival, nearly every single contact urged Charles to return to France; he persuaded enough to support him but was dependent on a small force mobilised by Donald Cameron of Lochiel and other Lochaber chiefs. O'Sullivan recalled Lochiel had "700 good men, but ill armed; Kapock arrived the same day, w[i]th about 350 clivor fellows". Cavalryman Sir John MacDonald, another of the 'Seven Men', later wrote that Lochiel admitted to lacking military experience; he therefore suggested that although either he or Francis Strickland could do the job of organising the Jacobite forces, O'Sullivan was the best qualified. O'Sullivan was accordingly installed as adjutant-general and quartermaster-general, handling personnel, training and logistics.
As more recruits came in, O'Sullivan organised them as a relatively conventional eighteenth-century army with a staff, cavalry, infantry, artillery, and supporting elements. Command of the field army originally rotated between Lord George Murray and the Duke of Perth, but at Falkirk and Culloden, O'Sullivan was in overall control. The two Scots acted as brigade commanders, with the addition of Perth's brother John Drummond after his arrival in late November.
Arguments over strategy after Prestonpans reflected deep divisions between the Scots and Charles' advisors, many of whom were Irish. They wanted the autonomous, Catholic Ireland promised by James II in 1689, which meant putting Charles on the British throne. The Scots who provided the bulk of the army were mostly Protestants who wanted to end the 1707 Union with England. They preferred to consolidate their position and resented the exiles, many of whom held French commissions and would be treated as prisoners of war if the Rising failed; the Scots risked execution and loss of their lands.
There were several disagreements on strategy in the Jacobite Council of War between its Scots and Irish members, particularly regarding the invasion of England. O'Sullivan supported the invasion in the face of the reservations of many Scots, despite his own concerns that their force was not large enough.