Born around 1550, Hugh O’Neill was the grandson of Conn Bacach, who had been created the first earl of Tyrone by Henry VIII under the ‘surrender and regrant’ scheme in 1542. In 1558, when Hugh was a young boy, his father was assassinated by his own stepbrother, Shane O’Neill. Fearing that Hugh would be killed next to remove any claim he might have to the Tyrone title, he was taken away from Ulster and put into foster care. In adulthood, he gradually rose to prominence and in 1587, he became the 2nd earl of Tyrone, which his uncle Shane had fought hard to secure but failed to accomplish. In August 1591, Hugh O’Neill eloped with Mabel Bagenal. Her brother Henry was furious, and it created a lot of animosity between the earl and the English government’s most senior representative in Ulster.

It is not unusual for major conflicts to start from relatively minor events. In May 1593, the Maguires of Fermanagh raised a large army, over 1000 men, and attacked Sligo in retaliation for an attack on their lands by a minor English official. This provoked a government response. Henry Bagenal and Hugh O’Neill put aside their differences and marched together into Fermanagh at the end of September. On 10th October (1593) when they reached the ford across the River Erne at Belleek, they found that Maguire’s men were ready and waiting for them. However, Hugh O’Neill led a cavalry charge across the river that caught the defenders by surprise, forcing them to retreat. In the confrontation he was wounded in the leg, but some historians have questioned whether the battle was simulated to make it appear that Hugh was loyal to the crown. In February 1594, Captain John Dowdall landed infantry and artillery at Enniskillen, the Maguire stronghold. After a 9-day siege, broken by an amphibious assault, the Maguire castle fell. It appeared that the architects of the turbulence in Ulster had been defeated. However, it marked the beginning of a conflict that has become known as the Nine Years War, and very soon, the entire region was engulfed in unrest. 

In June, Hugh Roe O’Donnell, Gaelic lord of neighbouring Tír Conaill (Donegal), besieged the English garrison that had taken over Enniskillen Castle. Previously, in January 1592, Hugh Roe managed to escape from custody in Dublin Castle, where he had been imprisoned for over four years, and made his way south across the Wicklow Mountains until he came to the safe refuge of none other than Feagh McHugh O’Byrne, who had defeated the English army in the Battle of Glenmalure in August 1580 during the outbreak of the Baltinglass Rebellion. The government in Dublin reacted by sending reinforcements to break O’Donnell’s siege at Enniskillen, however, the English were stopped by the Maguires at a ford on the River Arney. The army’s supplies and food rations were abandoned at the ford, which became known afterwards at the Ford of the Biscuits. This was the first of many more serious embarrassments for the English army still to come. 

At the end of August 1594, reinforcements finally arrived to relieve the desperate English garrison at Enniskillen, led by the new lord deputy himself, Sir William Russell. Returning to Dublin shortly later, in January 1595, Russell led an assault into the Wicklow Mountains, in search of Feagh McHugh O’Byrne. This was the moment that Hugh O’Neill, earl of Tyrone, decided to make a definitive stand against the crown. Blackwater fort had been constructed twenty years previously to house an English garrison, provocatively situated on the River Blackwater, which formed the border between Armagh and Hugh O’Neill’s heartlands of Tyrone. It was a large square fort defended by two corner towers, not unlike Fort Protector, built immediately prior to the Plantation of Leinster. Nearby, was a wooden bridge across the Blackwater, which had a stone gate on the Tyrone side of the river, and a wooden tower on the Armagh side, adjoining the fort itself. It was designed to accommodate up to 200 soldiers, but at the beginning of 1595, the garrison was much smaller, perhaps as few as 25 soldiers. Early in the morning of 16th February 1595, Hugh O’Neill watched nearby as his men overcame the garrison and took the fort. Over the next few days, they dismantled both the bridge and the fort, thereby removing the symbol of English military power from the doorstep of Tyrone.

Over the next few months, O’Neill’s men attacked and burned the English settlements and garrisons in the nearby counties of Louth, Meath and Monaghan, while his Donegal ally Hugh Roe O’Donnell similarly raided into Sligo, Roscommon and Cavan. The English garrisons at Enniskillen and Monaghan were powerless to react, and fearful that the fate of Blackwater would befall them if they did. Slow to respond at first, the government eventually tasked Hugh O’Neill’s brother-in-law, Henry Bagenal, with the job of resupplying the English garrison at Monaghan town. He assembled his large army at Newry, and marched to Monaghan on 25th May. O’Neill’s men harassed the English army on their march to Monaghan but did not prevent them from reaching the fort. Having successfully resupplied the fort and replaced the garrison with fresh troops, he now began the return journey to Newry. This was the moment that Hugh O’Neill chose to strike. As soon as Bagenal and his men were out of reach of the fort, Hugh’s forces began to attack. By the time the English reached Clontibret Church they found themselves surrounded. In the intense encounter that followed, Hugh was pulled from his horse, but he killed his assailant with his knife. After eight hours of fighting and skirmishing, both sides ran short of ammunition and the battle ended without either side securing a win. However, the outcome was seen as a defeat for the English army. They found O’Neill’s soldiers well-armed, highly organised and tactical, far more formidable than anything encountered during the Desmond Rebellion fifteen years earlier.

While Hugh may have been the earl of Tyrone, Turlough Luineach O’Neill was in fact the chief O’Neill recognised under Gaelic law, a position he held for nearly 30 years, until his death in September 1595. Hugh now made his way to Tullahoge and was inaugurated chief of the O’Neill. From this point on he signed his correspondence ‘O’Neill’ and abandoned the use of his English title, earl of Tyrone. He also opened communications with Philip II of Spain in search of military support. At the same time, he offered a truce to the lord deputy, William Russell, who cautiously accepted. Hugh was deliberately giving an impression of a peaceful resolution but, in reality, he was buying time. He quickly began stockpiling provisions in anticipation of the arrival of a new Spanish armada, but any support from Spain would not arrive for several more years.

In 1597, a new lord deputy arrived, Lord Thomas Burgh, and from the outset he was determined to confront Hugh O’Neill. In July that year he marched north to Armagh, where he resupplied the English garrison there, and headed to the site of the demolished fort on the River Blackwater. In the space of two weeks, his men built a new fort, this time on the Tyrone side of the river. However, the lord deputy took ill in October and died in Newry. The English momentum in undermining Hugh’s position stalled. O’Neill now took the opportunity to make an alliance with James MacSorley MacDonnell, chief of the Scots of Antrim, who proceeded to attack the English garrison at Carrickfergus Castle, killing the commander, Sir John Chichester, and sending his head to Hugh. Despite this, Hugh once again sent word to the government that he wanted to discuss a peaceful resolution. In December 1597, O’Neill met Thomas Butler, 10th earl of Ormond, at Dundalk. Butler was in command of the crown forces in Ireland since the death of Thomas Burgh. A ceasefire was agreed, but this time it was the English who were keen to gain more time to plan their next move.

That move came in August 1598, when Hugh’s brother-in-law and old adversary, Henry Bagenal, marched north in Ulster with a large army, 3500 foot-soldiers and 350 horsemen, as well as heavy artillery. On 15th August, the army left Armagh towards Blackwater Fort to relieve the garrison that was stationed there since it had been rebuilt by Thomas Burgh a year earlier. The garrison was overjoyed at the sight of the English army approaching the fort. However, their celebrations were premature. As the approaching army crossed the wet, boggy ground known as the Yellow Ford, they were pinned down by O’Neill’s waiting soldiers. In the battle that ensued, the English army was decisively beaten, and Henry Bagenal was forced to retreat in disgrace. Having utterly failed to overcome Hugh O’Neill by taking the offensive, and powerless to contain the situation in Ulster, the English were now forced on the defensive. Within weeks of Hugh’s victory at the Yellow Ford, the unrest had spread south to Munster, where the English plantation became the target of reprisal attacks. Many of the settlers, such as Edmund Spenser, fled their estates. Hugh stoked the situation further when he conferred on James fitzThomas fitzGerald the earldom of Desmond. Also known as the súgan earl (the Irish word for straw, to describe his tenuous claim to the earldom), James was a nephew of Gerald fitzGerald, the 15th earl. Since Gerald’s death in 1583, which marked the close of the Desmond Rebellion, the earldom had not been reinstated by the crown. By doing so now, Hugh O’Neill was effectively assuming the duties of a monarch.

To make matters worse for the English in Ireland, they were now leaderless. In December, the queen appointed Robert Devereux, 2nd earl of Essex, as lord lieutenant, but he did not arrive until April 1599. The earl of Essex initially attempted to restore peace in Munster, and at the end of August marched north to confront Hugh O’Neill. In the end, there was no confrontation. Instead, he had a secret meeting with Hugh, the culmination of which was another truce. Queen Elizabeth, who had previously welcomed Hugh’s previous offers of truce, was on this occasion furious that the earl of Essex had backed-down from a confrontation. He left for England in September, and the English administration in Dublin was once again left without a senior royal official. No sooner had he left, Hugh O’Neill ended the ceasefire when he marched south, almost as far as Cork city. His objective was to encourage the uprising in Munster. The fact that he could lead his Ulster army from one end of the country to the other, without any opposition, symbolised the impotency of the crown’s administration in Ireland, and echoed the similar position that the English crown found itself in during the Bruce invasion of Ireland nearly 300 years earlier. In February 1600, a new lord deputy arrived, Charles Blount, 8th baron Mountjoy. 

Mountjoy’s arrival would change the momentum of the war, though this was not obvious at the outset. He did not attempt to confront O’Neill within the first weeks or months of his arrival. He realised that he first needed to restore morale and discipline within the royal army. He treated desertion with a firm hand, hanging 16 English soldiers who tried to make for home in April. He also reorganised the way in which the army was mobilised. For example, he reduced the dependence on the baggage trains that had been used to supply the army as it moved through the countryside. The supply train had been the weakness of the engagement in 1594 that gave its name to the Ford of the Biscuits. Mountjoy realised that he needed his soldiers to be mobile, agile, and fast if they were going to engage O’Neill in Ulster, where supply was less of an issue for soldiers defending their home ground. He also proposed constructing more garrisoned forts around the edge of O’Neill’s homelands. These forts could maintain the supplies that the army needed and make movement throughout the region safer for the troops. Mountjoy also provided a greater level of training for his soldiers to prepare them for battle. Finally, he reduced the amount of equipment that his foot soldiers had to carry, creating an early form of light infantry, which became synonymous with the British army in later centuries. In effect, he modernised the royal army in Ireland.

As well as modernising the royal army, Mountjoy was more careful in his tactical planning to undermine O’Neill. Key to this was the establishment of a garrison to the northwest of Tyrone, which would expose O’Neill on two fronts instead of just one. On 14th May, ships landed a substantial force on Lough Foyle and quickly established a fort at Culmore, near Derry. A few days before their landing, Mountjoy had marched into Ulster from the south, distracting Hugh O’Neill long enough to ensure the army landing on Lough Foyle would meet little resistance there. 

One of those who arrived in Ireland with Mountjoy was Sir George Carew, who had been appointed as the new president of Munster. George had served as constable of Carlow Castle in 1576 and was a veteran of the Desmond and Baltinglass Rebellions, having witnessed the defeat of the English army at the Battle of Glenmalure, where his brother Peter was killed. George Carew’s task as president was to restore peace to Munster, which he effected through diplomatic means rather than military force. To ensure that the links between Munster and Ulster were broken, Mountjoy himself pacified the midland counties of Kildare, Laois and Offaly. In this way, Hugh O’Neill was isolated in Tyrone. Now Mountjoy began to close the net. Along the eastern borders of Tyrone, Mountjoy began a campaign of fort construction, while Hugh created defensive positions within Tyrone itself to block any invasion. The two sides were preparing for an encounter that would prove definitive. In the end, that encounter would not take place in Ulster, instead, it would be convened in Munster.

On 21st September, 1601, a Spanish fleet was spotted off the Old Head of Kinsale in Cork. When the Armada arrived in Ireland in September 1588, it had been purely accidental. This time it was no accident. The most recent armada had nearly suffered a similar fate, and several of the ships that had left Lisbon a month earlier were forced back to due stormy conditions. As a result, of the 4500 Spanish soldiers that had left Lisbon, only 1700 arrived in Kinsale, under the command of Don Juan del Águila. Mountjoy acted swiftly, and by the 1st of November the Spanish were contained within the town itself, while the English fleet blockaded the harbour. Having anticipated Spanish assistance for some time, the location of their recent landing was problematic for Hugh. It took him several weeks to make the necessary preparations, and it wasn’t until 9th November that he left Tyrone on the long march to Cork. Emboldened by the Spanish arrival, his closest ally, Hugh Roe O’Donnell, had rendezvoused with his followers from Connaught and Donegal at Ballymote Castle on 23rd October, and was already en route to Munster. 

The Spanish arrival at Kinsale had acted like a magnet, drawing the two sides together into a long overdue confrontation. On 7th December, Hugh O’Neill and Hugh Roe O’Donnell met at Bandon, where they combined forces with a large army raised in Munster. By now, a further 650 Spanish troops had arrived under the command of Don Pedro de Zubiar, who secured further coastal locations to the west of Kinsale. Finally, on Christmas Eve they marched towards Kinsale to confront the waiting English army, and lift the siege of the Spanish who still held out in Kinsale. Having used tactics to outsmart the English army so often before, O’Neill was ill-prepared for the confrontation with Mountjoy’s modernised army. Hugh now plunged into the same trap that the English had fallen into when they attacked him on home ground in Ulster. Within a few hours, O’Neill’s alliance had been convincingly defeated. On St Stephen’s Day, Hugh began his return journey home. The next day, O’Donnell took a ship to Spain to appeal for further reinforcements, but he died there in August. Despite several more valiant attempts by the Spanish in Kinsale to break the siege, Águila agreed to a truce on the 2nd January, 1602, and was allowed to return the Spain. Hugh O’Neill arrived home to Tyrone on 10th January. The march to Kinsale and back had cost him dearly, literally, and metaphorically. Over the months that followed, the English focused on the clean-up operations around Kinsale. In June, Mountjoy marched into Tyrone, forcing Hugh into hiding. To add insult to injury, he built a large bastion-style fort on the shores of Lough Neagh, close to O’Neill’s family home at Dungannon, which would become known as Mountjoy Fort. On 29th August Mountjoy marched to Tullahoge, and in a highly symbolic act, he destroyed the stone chair that had been used for centuries during the ceremonial inaugurations of the O’Neill chiefs, including Hugh himself. 

On 30th March, 1603, after two years on the run. Hugh O’Neill submitted to Mountjoy at Mellifont Abbey, founded by St Malacy in 1142, and now the home of Sir Garret Moore. Unbeknownst to Hugh, queen Elizabeth had died six days earlier. In the end, this may have been to his advantage, as Mountjoy was not constrained by the wishes of the queen and proved more generous than O’Neill might otherwise have expected. In what became known as the Treaty of Mellifont, Mountjoy agreed that Hugh would receive a royal pardon and could retain the ‘English’ earldom of Tyrone if he abandoned the Gaelic title of O’Neill. Shortly later, Rory O’Donnell, Hugh Roe’s son, was created 1st earl of Tyrconnell. At a glance, it appeared that O’Neill and O’Donnell had resumed the positions their families held prior to the outbreak of the war. However, everything had changed around them. In 1607, Hugh O’Neill and Rory O’Donnell sailed from Rathmullan, Co. Donegal. They left for the continent, never to return, in what has become immortalised as the Flight of the Earls. Their removal from Ulster allowed for the final piece of the English conquest jigsaw, the plantation of Ulster. The 1603 Treaty of Mellifont and the 1607 Flight of the Earls were consequential events that mark the opening chapters of modern Irish history. They pivoted on Hugh O’Neill’s defeat at the 1601 Battle of Kinsale, which in the course of just a few hours, marked a definitive conclusion to the medieval way of life in Ireland. Had the result been different, so too might the future of Ireland’s modern history.