The latter involved Royalists, Gaelic Catholic leader Eoghan Ó Néill, and Presbyterian militia known as the Laggan Army, supported by Scots Covenanters under Robert Munro.

The Covenanter government, who provided support for Scottish settlers in Ulster, considered Cromwell and other leaders of the new Commonwealth of England dangerous political and religious radicals.

As Scots, they objected to the execution of their king by the English; as Presbyterians, they viewed monarchy as divinely ordained, making it also sacrilegious, and transferred their allegiance to his son, Charles II of England.

After capturing Drogheda on 11 September, his main force headed south towards Wexford; Colonel Robert Venables was sent north with three regiments, or around 2,500 men, to take control of Ulster.

These were accompanied by the mass expulsion of Scots settlers, as punishment for their defection; when Coote captured Coleraine on 15 September, he massacred the largely Scottish garrison.

[8] At the end of October, Coote joined Venables at Belfast; they spent November reducing remaining Royalist garrisons in the north, and in early December, assembled 3,000 men to attack Carrickfergus.

When the main body of the Parliamentarian force appeared, retreat rapidly turned into a rout, the majority fleeing without firing a shot; in the pursuit that followed, they lost 1,500 men, killed or captured, along with their baggage train and supplies.

Early in 1650, Monro agreed to evacuate Enniskillen for £500, and returned to Scotland, leaving Ó Néill's army as the only remaining obstacle to Parliamentarian control of the north.