The Assassination that Sparked the Irish Civil War

Thursday, the 22nd of June, 1922, was a bright and pleasant day in London. The city was going about its usual business under a warm summer sun. Field Marshal Sir Henry Wilson, a towering figure in the British establishment, had spent the morning performing a public duty. He had travelled to Liverpool Street Station to unveil a war memorial dedicated to the railwaymen who had died in the Great War. It was a solemn occasion, one of many such events happening across the country as Britain remembered its fallen. Sir Henry, dressed in his full Field Marshal's uniform, gave a speech and then returned home, taking a taxi to his house at No.36 Eaton Square, one of London's most fashionable addresses. The taxi pulled up outside the elegant white-fronted house just after 2 o'clock in the afternoon. Sir Henry Wilson paid the driver and stepped out onto the pavement. At 58 years old, he was still an imposing man, tall and with a distinctive, angular face. He had recently retired from a long and distinguished military career to enter the world of politics. As he fumbled for his house keys, two men, who had been waiting nearby, approached him. The quiet calm of the afternoon was about to be shattered in the most brutal and public way imaginable. This single violent act would send shockwaves across two islands and push Ireland over the precipice into a bitter civil war. 

The two men were not there to greet the famous soldier. They were there to end his life. As Wilson turned towards his front door, they drew their pistols. Without a word, they opened fire. Multiple shots rang out across the quiet, respectable square. The Field Marshal was hit several times. He staggered, dropping his keys and sword before collapsing onto his own doorstep. The assassins were quick and ruthless. They had chosen their moment carefully, targeting one of the most senior and symbolic figures of the British Empire right outside his own home. The attack was over in seconds, leaving a scene of chaos and horror on the sun-drenched pavement. The noise of the gunshots echoed through the neighbourhood drawing people to their windows and into the street. The two attackers did not linger. Their deadly work done, they turned and began to run, hoping to disappear into the maze of London streets. but their escape would not be so easy. The sound of the attack and the sight of the fallen Field Marshal had instantly alerted passers-by and residents. A chase began immediately, with ordinary citizens and off-duty policemen pursuing the gunmen. The quiet elegance of Eaton Square had just become the stage for a desperate manhunt, and the consequences of this violent afternoon were only just beginning to unfold for Britain, and most especially for Ireland. Who was this man whose death caused such a stir? Field Marshal Sir Henry Wilson was not just any soldier. He was born in County Longford, Ireland in 1864 into a wealthy, land-owning Anglo-Irish Protestant family. From a young age he was groomed to be part of the British establishment that ruled Ireland and a vast global empire. He embarked on a military career in 1881 and through ambition and intellect he climbed the ranks of the British Army. By the time of the Great War, he was one of its most important generals, serving as a crucial link between the British and French High Commands. His career culminated in his appointment as Chief of the Imperial General Staff, the professional head of the British Army from 1918 to 1922. Wilson was more than just a soldier. He was a passionate and uncompromising political figure. He was a staunch Irish unionist, meaning he believed with every fibre of his being that Ireland should remain part of the United Kingdom. He fiercely opposed any move towards Irish home rule or self-government. His political views were so strong that in 1914, during the Curragh mutiny, he secretly advised fellow officers that they should resign rather than enforce home rule on the resistant Unionists of Ulster. This act of defiance helped to poison the political atmosphere and pushed Irish nationalists towards more radical, violent solutions to achieve their goals. During the Irish War of Independence, which raged from 1919 to 1921, Wilson became a hate figure for Irish Republicans.

 From his powerful position in London, he consistently argued for a harsher, more brutal military campaign to crush the Irish Republican Army, or IRA. He openly clashed with British commanders in Ireland, whom he felt were too soft on the rebels. When a truce was finally agreed in July 1921 to end the fighting, Wilson was disgusted. He saw it as a surrender to terrorism, and called the political agreement rank, filthy cowardice. To him, the fight for Irish independence was nothing short of a rebellion that had to be put down with overwhelming force. After retiring from the army in early 1922, Wilson did not fade into a quiet life. He immediately entered politics becoming a unionist member of parliament for North down in Northern Ireland. He also took on the role of a military advisor to the new government of Northern Ireland, which had been created a year earlier. In this position, he was blamed by many nationalists for encouraging the violent suppression of the Catholic minority in the North. Michael Collins, the leader of the emerging Irish Free State, described Wilson as a violent orange partisan. For Irish Republicans, Sir Henry Wilson was the embodiment of British oppression and the primary obstacle to a united, independent Ireland. The assassination of Sir Henry Wilson did not happen in a vacuum. In June 1922, Ireland was a nation on a knife edge, simmering with tension and deeply divided. The country had just emerged from the brutal war of independence against Britain. The fighting had ended with the signing of the Anglo-Irish Treaty in December 1921.This treaty offered Ireland a significant degree of independence as the Irish Free State, but it came at a high price. The new state would remain part of the British Empire, its members of parliament would have to swear an oath of allegiance to the British monarch, and, most contentiously, it accepted the partition of the island, leaving the six counties of Northern Ireland under British rule. This compromise tore the Irish independence movement apart. The IRA, which had fought so unitedly against the British, split into two hostile factions. On one side were those who supported the treaty, led by Michael Collins. They argued that it was the best deal possible and a stepping stone to full independence. On the other side were the anti-treaty Republicans, who saw the agreement as a profound betrayal of the Irish Republic that had been declared in 1916.They refused to accept the partition of their country or any oath to a British king. This division was not just political, it was personal and deeply emotional, setting former comrades against one another. The atmosphere grew more toxic with each passing day. Just a week before Wilson's death, a general election was held in Southern Ireland. The results gave a clear victory to the pro-treaty side, giving Michael Collins and his provisional government a democratic mandate to establish the new free state. However, the anti-treaty IRA refused to accept the outcome .In an open act of defiance, a group of hard line Republicans had seized the four courts, Dublin's main legal complex, and turned it into a fortified headquarters. From this base, they challenged the authority of the provisional government, creating a tense standoff in the heart of the capital. Meanwhile, violence was spiralling out of control in the newly formed state of Northern Ireland. Sectarian clashes between Catholic nationalists and Protestant unionists, often involving the new police force, the Ulster Special Constabulary, were becoming commonplace. In a strange twist, Michael Collins was secretly cooperating with parts of the anti-treaty IRA in a clandestine military campaign against the Northern state, even as he prepared to confront them in the South of Ireland was a powder keg, the country was split, Dublin was in a state of armed standoff, and the North was bleeding. All that was needed was a spark to ignite the flame of civil war. The two men who waited for Sir Henry Wilson on that June afternoon were not common criminals. They were soldiers. Just like their victim. But they had fought for a different cause and ended up on a different path. Their names were Reginald Dunne and Joseph O'Sullivan. Both were London-born men of Irish descent and both were veterans of the British Army who had served with distinction during the First World War. Their personal stories reflect the complex loyalties and identities of the time. They had worn the king's uniform and fought for the empire, only to turn against it in the name of Irish freedom. Reginald Dunne, age 24, was the leader of the operation. He was a committed member of the Irish Republican Army in London. Before his turn to republicanism, he had served as a private in the British Army's Irish Guards. He had seen the horrors of the Western Front and had come to believe that Ireland deserved its independence. He was known as a dedicated and serious young man, deeply involved in the IRA's activities in the British capital. It was his planning and conviction that drove the plot to assassinate Wilson, a man he saw as a chief architect of Ireland's suffering, particularly the persecution of Catholics in Northern Ireland. His accomplice, Joseph O'Sullivan, was 24 years old as well. His story was particularly poignant. He too had joined the British Army to fight in the Great War. At the terrible Third Battle of Ypres in 1917, he had been so severely wounded that his right leg had to be amputated below the knee. He now walked with a wooden leg, a permanent and painful reminder of his service to the British Empire. Despite this sacrifice, O'Sullivan became a fervent Irish Republican. The struggle for his ancestral homeland became his new cause, and his disability did not deter him from taking on one of the most dangerous missions the IRA could conceive. 

For Dunne and O'Sullivan, killing Wilson was not murder, it was an act of war. They saw the Field Marshal as a legitimate military target. In their eyes, he was an enemy commander who was actively directing a campaign of violence against their people in the north of Ireland. They believed that by eliminating him, they would be striking a blow for justice and defending the vulnerable nationalist community. They were fully aware of the risks they were taking. They were attacking one of the most famous men in the country in broad daylight, and they knew that their chances of escape were slim. Their actions were those of men who had made a deliberate and fatal choice. The assassination itself was executed with a cold and brutal efficiency. As Sir Henry Wilson stood on his doorstep, searching for his keys after paying his taxi driver, Dunne and O'Sullivan made their move. They walked calmly towards him, closing the distance before their target could react. Wilson was in his full, ceremonial uniform, complete with his sword, making him an unmistakable figure. The men pulled out their revolvers and, from close range, fired a volley of shots. The sudden crack of gunfire shattered the afternoon peace of Eaton Square, a sound utterly alien to this wealthy and orderly part of London. Wilson was hit multiple times in the chest and legs. He cried out in pain and surprise, dropping the items he was holding as he crumpled to the ground. He attempted to draw his own sword to defend himself, a final, futile act of a lifelong soldier, but he was already mortally wounded. He collapsed onto the top step of his own home, the place where he should have been safest. The assassins did not hesitate. To ensure their work was done, they fired again at the fallen Field Marshal before turning to make their escape. The entire attack lasted mere seconds, a swift and shocking eruption of political violence on a London street. The plan for the escape was, however, far less successful than the attack. The noise had drawn immediate attention. A passing taxi driver, servants from nearby houses, and a number of pedestrians witnessed the event and instantly gave chase. Dunn and O'Sullivan ran, but O'Sullivan's wooden leg made a swift getaway almost impossible. They fired their weapons at their pursuers, trying to scare them off. In the ensuing chaos, they managed to shoot and wound two policemen and a civilian who tried to apprehend them. Their desperation was clear as they tried to fight their way through the growing crowd. The chase did not last long. The angry crowd, horrified by what they had just witnessed, surrounded the two men. They were cornered, outnumbered, and, in O'Sullivan's case, physically unable to keep running. Some in the crowd began to attack them, and it is likely they would have been beaten to death on the spot had the police not intervened. Officers managed to push through the furious mob and formally arrest the two assassins. Covered in bruises and with their clothes torn, Reginald Dunn and Joseph O'Sullivan were taken into custody, their brief, violent mission having come to a dramatic and public end. The arrest of Reginald Dunne and Joseph O'Sullivan was as chaotic and public as the assassination itself. Hemmed in by a furious mob that was baying for their blood, the two men were disarmed and taken by the police. In a way their capture by the authorities probably saved their lives from the immediate threat of being lynched by the enraged citizens of London. They were taken to a nearby police station, where the formal process of investigation and justice began. The British state, having just lost one of its most celebrated military leaders, now had his killers in its hands, and it intended to make an example of them. The trial of Dunne and O'Sullivan was held at the Old Bailey, London's central criminal court, just a few weeks later. The case against them was overwhelming. They had been caught in the act, with their weapons, and there were dozens of eyewitnesses to the crime. There was no question of their guilt in the eyes of the law. The two men did not deny their actions. Instead, their defence was a political one. They attempted to use the courtroom as a platform to justify what they had done, transforming their trial for murder into a trial of British policy in Ireland. The key moment of the trial came when Reginald Dunne delivered a powerful and moving speech from the dock. He did not ask for mercy. Instead, he spoke of the reasons for their actions. He talked about the suffering of the Irish people and the violence being inflicted upon the Catholic community in Northern Ireland. He declared that he and O'Sullivan had acted to avenge these wrongs. He said, You can condemn us to death today, but you cannot deprive us of the belief that what we have done was necessary to preserve the lives and the happiness of our countrymen in Ireland. He presented the assassination not as a crime, but as a duty. Despite the passion of Dunn's speech, the verdict was never in doubt. The jury quickly found both men guilty of murder. The judge sentenced them to death by hanging. On the 10th of August 1922, less than two months after they had shot Sir Henry Wilson, Reginald Dunn and Joseph O'Sullivan were executed at Wandsworth Prison. They went to their deaths calmly, convinced that they were martyrs for the cause of Irish freedom. Their bodies were buried in the prison grounds and for the Republican movement in Ireland, they became heroes who had made the ultimate sacrifice for their country. While Dunne and O'Sullivan faced their fate, a crucial question remained unanswered, a question that has puzzled historians for over a century. Who ordered the assassination? The two gunmen never revealed who had sent them. British investigators at the time, from Scotland Yard to the Home Secretary, conducted a thorough inquiry. They could find no concrete evidence linking the assassins to any official orders from a higher authority within the IRA. Their official conclusion was that Dunne and O'Sullivan might have been acting on their own initiative, or perhaps on the orders of a local London IRA branch, driven by their own fury at events in Ireland. However, suspicion immediately fell upon one man in particular, Michael Collins. As the head of the Irish Provisional Government and a key leader of the pro-treaty IRA, Collins was the most powerful figure in nationalist Ireland. There is strong, though circumstantial, evidence suggesting his involvement. Sir Henry Wilson was a bitter personal and political enemy of Collins. More importantly, Collins was deeply concerned about the ongoing violence against Catholics in Northern Ireland, and may have seen Wilson's death as a necessary act of retaliation. Several of Collins' closest associates later claimed that he had either arranged it or was very pleased when he heard the news. Another piece of the puzzle is that Collins reportedly tried to organize a rescue attempt for Dunne and O'Sullivan while they were awaiting trial, which suggests he felt a degree of responsibility for them. The motive for Collins might have been complex. Perhaps he hoped that killing a common enemy like Wilson could help to reunite the fractured IRA, bringing the anti-treaty side back into the fold for a renewed fight against the North. It would have been a desperate gamble, an attempt to divert attention from the looming civil war by creating a new conflict with an old enemy. But if Collins did give the order, he took the secret to his grave, as he himself was assassinated just two months later. The other main suspect was the anti-treaty IRA, particularly the group occupying the four courts in Dublin. The British government certainly believed they were responsible. However, the leadership in the four courts seemed genuinely surprised by the news of Wilson's death. While they certainly approved of the act, there is no evidence to suggest they planned or ordered it. This leaves the tantalizing possibility that Dunne and O'Sullivan were indeed freelancers, acting on their own great hatred of Wilson. The mystery remains. Was it a state-sanctioned execution by Collins, a rogue operation, or an act of revolutionary spite by the anti-Treaties? The truth remains buried in the past. The assassination of Sir Henry Wilson in the heart of London sent a shockwave through the British government. They were outraged and horrified that such a prominent figure could be gunned down in broad daylight. Their immediate reaction was to blame the most visible symbol of Irish Republican defiance. The anti-treaty IRA garrison that was occupying the four courts in Dublin. The British Prime Minister, David Lloyd George, and his cabinet were convinced that the order had come from them. They saw the occupation of the four courts and the murder of Wilson as part of the same Republican conspiracy to wreck the Anglo-Irish Treaty. On the very day of the assassination, the 22nd of June, the British government sent a furious ultimatum to Michael Collins and his provisional government. The message was blunt and uncompromising. Lloyd George demanded that Collins take immediate action to remove the IRA rebels from the four courts. The British stated that the ambiguous position of the Irish Republican Army can no longer be tolerated. The ultimatum carried a clear threat. If the Irish Provisional Government did not act, the British Army would. The British were prepared to use their own troops and artillery to attack the Four Courts and crush the rebels themselves. This placed Michael Collins in an impossible position. He had been desperately trying to avoid a direct conflict with his former comrades in the anti-treaty IRA. He knew that attacking the four courts would start a civil war, a conflict of Irishmen against Irishmen, which he dreaded. However, the British ultimatum left him with no choice. If he refused to act, the British would intervene, which would shatter the newly won independence granted by the treaty. 

The Irish Free State would be seen as a puppet government, unable to control its own capital, and the war with Britain would likely restart. Faced with these two terrible options, Collins chose what he saw as the lesser of two evils. To preserve the free state and the independence he had negotiated, he had to confront the anti-treaty rebels. The British cabinet had already ordered their own general in Ireland, Neville McCready, to prepare an assault on the four courts. McCready, however, delayed, giving Collins a final chance to act himself. After several more days of tense negotiation and failed appeals, the decision was made. Six days after Wilson's death, on the 28th of June 1922, troops of the new Irish National Army, using artillery borrowed from the British, opened fire on the Four Courts. The Irish Civil War had begun. The assassination of Field Marshal Sir Henry Wilson is often called Ireland's Sarajevo. Just as the assassination of Archduke Franz Ferdinand in 1914 was the trigger that plunged Europe into the First World War, the killing of Wilson was the direct catalyst for the Irish Civil War. While the deep divisions over the Anglo-Irish Treaty made a conflict almost inevitable, it was Wilson's death that forced the issue. It provided the British government with the justification to issue its ultimatum. which in turn compelled Michael Collins to open fire on his former comrades. The shots fired in Eaton Square found their echo six days later in the cannon fire directed at the four courts. The Irish Civil War that followed was a short but exceptionally bitter conflict, lasting around nine months. It pitted the pro-treaty National Army against the anti-treaty IRA. The fighting was brutal, characterized by ambushes, assassinations and cruel executions on both sides. It left a deeper and more lasting scar on Irish society than the war of independence that had preceded it. The conflict claimed the lives of many of the leaders of the independence movement, including Michael Collins himself, who was killed in an ambush in his native county Cork just two months after Wilson. The divisions created by the Civil War would dominate Irish politics for the rest of the 20th century. The importance of this event in British and Irish history cannot be overstated. For Britain, the murder of Wilson represented the shocking reach of Irish political violence into the very heart of its empire. He was the most senior British political or military figure killed during the entire Irish Revolution, and his death marked a final, violent chapter in the long and troubled relationship between the two islands. In 2022, a century after his death, a commemorative plaque was placed in his honour in the House of Commons, a testament to his enduring status as a major, if controversial, figure in British history. Today, the story of Wilson's assassination serves as a powerful reminder of how a single act of violence can have devastating and unforeseen consequences. It highlights the intense passions, personal hatreds, and complex loyalties that define the Irish revolutionary period.

 The mystery of who truly gave the order adds a layer of intrigue to a tragedy that pushed a nation already on the brink into a fratricidal war. The legacy of that conflict, born on a sunny afternoon in London, shaped the political landscape of modern Ireland and left behind wounds that took many decades to heal. It remains a pivotal and tragic moment in the shared history of two nations.