Based on an article by John Dorney
The fortress of Duncannon would prove to be one of the more strategically important fortresses in Ireland during the wars of the 1640s, with the fort being besieged on three occasions within the span of a decade. Of these, the most significant was the Siege of 1645. In this year, an Irish Catholic Confederate army under Thomas Preston besieged and successfully took the town of Duncannon in south eastern Ireland from its English Parliamentarian garrison.
Duncannon had formidable modern defenses, and it overlooked the sea route to Waterford and New Ross, two of the most important Catholic held towns in Ireland in the 1640s, and also ports at which the Confederates received military aid from Catholic Europe. Gunfire from cannon in the fort had the potential to harass or deter any shipping heading to these important towns.
The 1645 siege was conducted with a high degree of technical skill, and it was the opinion of the prominent Confederate leader Castlehaven that the siege of Duncannon was the only 'regular' siege in Ireland during this decade of warfare (i.e. the only siege where trenches & batteries were laid out systematically by the attackers). (Castles & fortifications in Ireland, P Kerrigan, pg 86)
Preston's troops were very well equipped, and the 1645 siege is also notable in being the first conflict in Ireland in which mortars were employed.
In the last weeks of 1641, the Kavanaghs and O'Byrnes, who sympathised with the objectives of the Northern insurgents, cleared the counties of Wicklow and Wexford of any opposition. The one place to successfully hold out was the formidable fort of Duncannon, under the command of the Lord Esmond. (Meehan pg 61)
By Christmas 1641, a scattered force of around 1000 Insurgents had deployed in a wide arc surrounding the fortress. The leaders of the Irish insurgents, Rossiter and Browne, had made Shelboggan, four miles from Duncannon, their headquarters, but most of the Irish were scattered in about in small groups in rudimentary fortifications or camps. Duncannon was not particularly hard to isolate, as it was located to the south of Wexford, overlooking Waterford harbour. That said, being on the water and so close to England, it could very easily be reinforced by ships from that Kingdom: In February 1642, the original garrison of 100 was reinforced by 200 soldiers under the Captains Aston and Weldon, along with six cannon. Duncannon was also located in a very strategically important position: Waterford harbour was a passage for ships heading to Waterford town and even (via the river Barrow) upstream to the town of Kilkenny. Duncannon was a major threat to these major towns, and the Irish were willing to devote a great deal of time and effort in taking the fortress.
Faced by this encirclement, the 300 defenders of the fort were by no means complacent. Raids were frequently employed against the attackers, with varied success. In one such an attack, a raiding party led by a Lieutenant Travis managed to surround a detachment of two-dozen Irish soldiers, inducing them to surrender. After these soldiers were brought to Duncannon, Esmond had most of them hanged. (Lenihan, Confed Catholics, pg 178) Brutality of this kind was the norm in the early stages of the war, but it would not be long before the Irish would have a chance to reciprocate.
Located not far from Duncannon Fort was Redmond's Hall, home to Alexander Redmond, a prominent local figure who was known to aid the Irish insurgents. Redmond's Hall was visible to the garrison at Duncannon, which can only have served as a constant reminder to the garrison of the sympathies of its owner. By mid summer, Captain Aston had become convinced that the hall could be easily taken and on 20 July 1642 took ship from Duncannon with around ninety men and two small cannon, landing near the Hall.
Alexander Redmond barricaded the Hall and prepared to defend it. The defenders, made up of mostly of members of the Redmond family and their tenants, numbered ten, all of whom were armed with fowling pieces.
Captain Aston drew his men up in front of the Hall and demanded admission in the name of the King. Alexander Redmond responded that he was welcome to come in, if he left his soldiers and weapons outside. This exchange of words was promptly swapped by a lengthy exchange of gunfire from both parties. Aston soon discovered that his cannon were too small to make much impression on the main door. To add to his troubles about half his men abandoned him to pillage the countryside. As the fight dragged on a heavy sea-mist descended on the area.
Captain Rossiter, still encamped at Shielbaggan, was alerted by the sound of gunfire. Organising a large party of soldiers, the force marched rapidly to the aid of the defenders in the hall and surprised the attackers under cover of the fog. About thirty of the English escaped to their boats and back to the fort, but most of the English were slain or captured. Captain Aston himself was one of those killed. Those taken prisoner included Lord Esmond's two nephews Lieutenants John and Walter Esmond. Several of the English prisoners were hanged the following day: another eleven were hanged at New Ross several days later. Amongst those executed was one of the Esmond brothers.
Needing to keep the passage of Waterford harbour open and also fearing the presence of an English garrison deep in their territory, the Confederates' Supreme Council in Kilkenny dispatched Thomas Preston, general of their Leinster Army, to take Duncannon in January 1645. Preston had at his disposal 1,300 men, four cannon and a mortar. 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 and firemaster named Nicholas La Loue. La Loue had served with Preston in Flanders and was chief of engineering in the Leinster Army.
Duncannon possessed formidable defenses. For one thing, it was located on a peninsula and could only be approached from the north, the other three sides jutting out into the sea. Just off the town were docked four Parliamentarian ships, which were supplying Duncannon with food and reinforcements. Secondly, it possessed two lines of fortifications, the outer line being a more modern low deep rampart protected by a dry ditch and the inner wall being a medieval curtain wall, complete with three towers. 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.
Preston arrived at Duncannon on January 20 and proceeded to construct a ring of trenches which cut off Duncannon on it landward side. From the hill that overlooked the town to the north, his guns were able to fire on a squadron of four Parliamentarian ships that were docked off Duncannon and providing the town with supplies. The Flagship, the Great Louis was badly damaged, its mast wrecked by cannon fire, and it took several more hits from the mortar as it tried to get away. The ship sunk in deep water, drowning its crew and 200 soldiers who had been on board.
Having cut off Duncannon's supply from the sea, Preston proceeded to dig saps closer to the walls, the ultimate aim being to bring his cannon close enough to the walls in order to blast a breach and open the way for an assault. His engineers also dug a mine underneath one of the town's bastions. All the while, the town's defenders were kept under a bombardment by the mortar and, as the Confederate troops got closer to the walls, by sharpshooters. On March 12, one of these marksmen killed the fort's second in command, one Captain Lurcan, who was hit in the head by a bullet.
On March 16, by which time the Irish trenches were, 'within pistol shot of the walls', Preston ordered the mine to be exploded, opening a breach in Duncannon's outer walls. The Irish infantry then assaulted the town, but were beaten off with some losses. The following day, St Patricks Day, Preston tried again and this time his troops succeeded taking the town's outer, more modern walls but were stopped at Duncannon's inner, medieval ramparts. They had succeeded in occupying one of the town's towers for an hour before being beaten back. Geoffrey Barron, a Confederate politician, who kept a diary of the siege, reported that 24 Irish soldiers were killed in the two assaults.
At this point, Preston summoned Esmond to surrender, before he had to, 'proceed to extremities'. 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. Esmond was also advised to surrender by the Parliamentarian vice admiral, William Smith, who was anchored off shore with seven ships, but could not break through to relieve the town. In a letter that reached Esmond on March 11, Smith had warned him that, 'if the rebels take the fort by storming it, they will undoubtedley put you all to death...you should agree with thy adversary while thou art in the way' (Lenihan, Confed Cath,pg 186.)Esmond had Smith's letter publicly read to his troops after the assaults of March 16-17 to discourage those who favoured holding out.
Alongside the risk of massacre, the English garrison was also very low on gunpowder and water. The town's only source of fresh water, a well, was behind the Confederate siege lines.
In light of these facts, Esmond formally surrendered Duncannon to Preston on March 18. The Confederates took possession of the town but its garrison was allowed to march away to Youghal, which was in Protestant hands. However, they had to leave behind the town's 18 artillery pieces. Esmond himself died a few days after the end of the siege. 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. Preston, who had for many years been the Spanish military governor of Leuven was highly experienced in siege warfare and his conduct of the siege drew widespread praise. Not only did he take the town, but he did so at a relatively low cost. Sixty seven Confederate soldiers died in the siege, of whom roughly 30 died of disease. 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.
The Great Lewis, the Parliamentarian ship sunk during the siege, was re-discovered in 1999 and raised in 2004.
Duncannon was besieged for a third time during the Cromwellian conquest of Ireland by the forces of the English Parliament, as part of the Siege of Waterford. It repelled a siege by Oliver Cromwell in 1649 but surrendered after a lengthy blockade by Henry Ireton in 1650.