O’Neill had roughly 1,500 men at his disposal inside the walls of the town, a decent number made of Tipperary natives and soldiers fleeing from Cromwell’s previous assaults. One of these men was Colonel Edmund Fennel, a Cork native. He had agreed a sum of money plus a full pardon for taking up arms against Cromwell if he opened the north gate at midnight and let roughly 500 of the parliamentarian soldiers gain access to the town. O’Neill was as untrusting as he was clever and when he did the nightly inspection of the guard at the north gate he had a suspicion treachery was afoot. He replaces Fennel's men with his own and when midnight came it was O’Neill’s men that greeted Cromwell’s troops. Cromwell lost 100's of men.
The larger guns requested by Cromwell had finally arrived and were positioned near the North gate of the town, the only viable entry Cromwell could attempt. Cromwell’s guns had more firing power than the walls or indeed the earthen ramparts could handle and on May 16th he breached the walls of Clonmel.
From that point on, Cromwell’s plan was of simple design and one which he saw success in other towns in Ireland. The following morning he planned for his infantry to enter the town through the 80ft breach in the town wall, push back O’Neill’s men and open the gate to allow access to Cromwell and his men. He would then take the town and complete his campaign in victory. Cromwell was aware that Clonmel was not as easily taken as other towns in Ireland, but he certainly was not prepared for what was to come.
Cromwell’s plan went ahead and the following morning men from his infantry scaled the rubble of the wall and entered Clonmel – and a slaughter! O’Neill, having experience with siege warfare from his time with the Spanish in Flanders used his skills to prepare for the onslaught which was to come. He had the defenses at the north gate strengthened by constructing a V shaped inner fortification made from earth and timber. This new construction was lined with Musketeers and two canons were placed either side. Cromwell’s men were trapped! With the rushing of their fellow soldiers coming up from behind and no way to advance forward, they were cut down by musket fire and chain shot from point blank range. Cromwell lost some 1,000 men while those who survived retreated back to their General. For the first time throughout his Irish campaign Cromwell was staring at potential defeat.
Not willing to let this happen, Cromwell tried to rally his men into making a second attempt at an attack. His infantry refused, instead suggesting he send in his Cavalry as they had better Armour and were better paid! He agreed and sent his men forward for a second attack. The cavalry, dismounted their horses and led by Colonels Culme and Sankey they entered through the breach in the wall and walked straight into the same situation as the infantry. The fighting lasted for some time and by the end of the day Cromwell’s men had enough and stumbled back over the rubble and bodies of their comrades to join their General once again. The victory that day went to O’Neill.
The exact number of casualties is not clear but estimations range from 1,500 to 2,500. In any case, that is the largest number of casualties that Cromwell’s New Model Army ever suffered during its existence. Captain Warr of the New Model Army later described the slaughter “Hugh DufiTs men within fell on those in the pound with shotts, pikes, scythes, stones and casting of great long pieces of timber with the engines amongst them and then two guns firing at them from the end of the pound, slaughtering them by the middle or knees with chained bullets, that in less than an hour’s time about a thousand men were killed in that pound, being a top one another”
Cromwell was not accustomed to defeat and he refused to give up. He ordered his men to remain near the breach and cut down any of O’Neill’s men who tried to repair or fortify the 80ft entry way. His soldiers, exhausted and disheartened refused his orders once again, a surprise for a commander who was used to enforcing his Iron will. A soldier from the new model army later wrote “neither the threats of the General nor the bloody swords of inferior officers was sufficient enough to keep them from turning tail to the assault”.
Within the town, things were different for O’Neill. He realised that aid from Ormond was unlikely to arrive at this point. He had lost many of his men, was out of ammunition, few weapons remained and very little food remained for his men or the towns people. He knew the only way to save the lives of his unarmed soldiers and the people of Clonmel was to retreat and evacuate. O’Neill formed a plan of escape. He approached the then Mayor of Clonmel – Mayor White and told him that he should seek talks with Cromwell and request generous terms for the safety of the town in return for its surrender. O’Neill requested that Mayor White not do this until both he and his men have left the town.
The night after the initial attack by Cromwell, knowing that the New Model Army were concentrated on the North gate of the town, under the cover of darkness O’Neill took his men and left via the South gate and crossed the River Suir to safety.
On the morning of the 18th Cromwell was trying hard to rally his troops for another attack on the town, when he received word that Mayor White was seeking terms for surrender. Desperate to bring his campaign to a close he offered generous terms – guaranteeing the lives and the property of the towns people. Once agreed Cromwell finally entered the town of Clonmel only to find it empty of O’Neill and his men.
Cromwell was furious to learn that O’Neill has escaped, even so he kept his word and the towns people were not harmed, but he sent his Cavalry after O’Neill and his men. A few stragglers were cut down by the Cromwellian forces but many, include O’Neill got way and were heading towards Waterford. Waterford, fearing the plague would not grant access to O’Neill or his men and in a bid to survive they split up and all made their way towards safety in Ulster.
Cromwell departed and made his way back to England to deal with the threat of the Scots and Charles II. Never before had Cromwell suffered such a loss of life as he had at Clonmel at the hands of High Dubh O’Neill. Speaking of O’Neill one of Cromwell’s Officers wrote “The stoutest enemy that ever was found by our army in Ireland, and it is in my opinion, and very many more, that there was never so hot a storm of so long a continuance, and so gallantly defended, neither in England nor in Ireland".
Painting- Original work of Cromwell Rallying his troops to attack Clonmel once again. Artist- Graham Turner