An Irish Catholic Confederate army under Thomas Preston besieged and successfully took the town of Duncannon in County Wexford from an English Parliamentarian garrison.

Esmond, under pressure from elements of his garrison, also changed to the side of Parliament and effectively re-declared war on the Catholic Confederates.

His motives are unclear: though he was a Protestant convert, the Esmonde family were Anglo-Irish Roman Catholics, and he owed his entire advancement to the Crown.

Needing to keep this channel open and also fearing the presence of an English garrison deep in their territory, the Confederates' Supreme Council in Kilkenny despatched Thomas Preston, general of their Leinster Army, to take Duncannon in January 1645.

The mortar, the first of its kind to be used in Ireland had been donated by Spain the previous year and was commanded by a French military engineer named Nicholas La Loue.

However, it had two grave weaknesses, first, it was overlooked by a hill to the north, from which an attacker could fire into the town and secondly the water supply was also located outside the walls.

This was a delicate threat, implying that if the town fell to an assault, its defenders would be put to the sword - as was customary in contemporary siege warfare.

Esmonde was also advised to surrender by the Parliamentarian vice admiral, William Smith, who was anchored offshore with seven ships, but could not break through to relieve the town.

In a letter that reached Esmonde on 11 March, Smith had warned him that, 'if the rebels take the fort by storming it, they will undoubtedly put you all to death...you should agree with thy adversary while thou art in the way'.

Preston would go on to briefly besiege Youghal, but bad weather, a lack of supplies and squabbling with Castlehaven, the Confederate Munster general, put an end to his campaign for that winter.

The siege was of importance in that it re-opened the sea route into Waterford and eliminated a hostile English garrison in Confederate territory.

Given that the campaign was conducted in mid-winter, in an age when disease routinely killed many more soldiers than combat, this represented a considerable logistical achievement on the part of the Irish general.