Special Report: British Rule in Ireland Part 1- The Cromwellian Conquest
By Senan Monks
November 2, 2026
Introduction
“It was a tragic necessity that the Irish should remember it; but it was far more tragic that the English forgot it. For he who has forgotten his sin is repeating it incessantly forever.”- GK Chesterton
Between 1649 and 1653, the Commonwealth of England conducted a military campaign in Ireland through its New Model Army (NMA), led by Oliver Cromwell. The goal was to reconquer the lands seized by the Irish Catholic Confederation following the 1641 Rebellion and defeat English Royalist forces in Ireland, who were seeking to restore the monarchy following the English Civil War (Ó Siochrú). These four years were marked by numerous atrocities, including civilian massacres, collective punishment, man-made famine and one of the largest forced population transfers in European history (Morrill). This report is the first of a two-part series about British Rule in Ireland. Part 1 gives an account of the atrocities of the Cromwellian conquest and assesses them in the context of the Genocide Convention and genocide case law. Part 2 will examine the centuries-long Protestant Ascendancy in Ireland against the 1973 Apartheid Convention to determine whether it can be considered a proto-apartheid system.
Massacres at Drogheda and Wexford
Cromwell invaded Ireland in August 1649, vowing to carry out the “great work against the barbarous and bloodthirsty Irish.” Opposing him was a tense alliance between the Irish Catholic Confederation and Royalist forces (Ó Siochrú).
The NMA first besieged Drogheda, about 50km north of Dublin. The NMA seized the town on September 11, with Cromwell ordering his troops to kill every combatant (Ó Siochrú). The NMA massacred around 3,500 Irish Confederate and Royalist soldiers. They also massacred a significant number of the Irish Catholic civilians, with modern estimates between 500 and 800+ civilian deaths. This included virtually all the Catholic clergy, who were especially targeted. Cromwell’s forces then marched southeast on Wexford, where a similar scene unfolded. After negotiations failed, the NMA attacked and quickly broke into the town (Ó Siochrú). The exact death toll of the subsequent massacre is estimated at 1,500-2,000, including hundreds of civilians. Contemporary sources say the civilian population of Wexford was reduced “to a very few” (Ó Siochrú 97), either murdered by the NMA or drowned in the River Slaney while trying to escape (Ó Siochrú).
Cromwell justified these massacres by stating that he was punishing Irish Catholics for the massacres of Protestant settlers during the 1641 rebellion. He further claimed that they would frighten the remaining enemies of the NMA into a quicker surrender.
Collective punishment and man-made famine
By summer 1650, Cromwell had conquered most of eastern Ireland, including Kilkenny, the capital of the Irish Catholic Confederation (Ó Siochrú). Cromwell returned to England, and the NMA was instructed to proceed west and capture the remaining cities (Ó Siochrú). Cromwell’s departure did not ease the suffering of the Irish population. Protracted sieges at Waterford and Limerick resulted in thousands of deaths, mostly due to starvation and plague. Furthermore, the beginning of a guerilla campaign by Irish forces in NMA-controlled lands ushered in the most violent part of the conquest (Canny).
From 1650, up to 30,000 Irish guerillas carried out ambushes on NMA soldiers in rural areas, where the Irish held superior knowledge of the landscape (Ó Siochrú). The NMA’s response was severe, and the general Irish Catholic population was targeted with collective punishment for the actions of the guerillas. Inhabitants of towns near ambush sites were extorted with high fines and anyone who fed or sheltered guerillas faced “immediate death” (Ó Siochrú 200). The NMA designated areas where guerillas were known to be active as no-go zones, and anyone found there, guerilla or civilian, would be "taken, slain and destroyed” (Ó Siochrú 211). Contemporary sources describe thousands of killings under these policies. One account from an English source wrote that the Irish countryside was filled with “dead men hanging on trees and gibbots. A sad spectacle but there’s no remedy, so perfidious are the people [Irish Catholics]” (Ó Siochrú 212).
As further punishment, the NMA systematically destroyed food stocks across Ireland, creating a man-made famine which killed tens of thousands through starvation and by exacerbating an ongoing plague epidemic (Ó Siochrú).
Forced population transfer
By late 1652, the resistance was largely defeated. The NMA hunted down the remaining guerillas and proclaimed Ireland pacified in late 1653 (Ó Siochrú). However, even as the armed conflict winded down, the atrocities continued, including one of the largest forced population transfers in European history (Morrill).
Forced population transfer occurred throughout the Cromwellian conquest. Thousands of Irish prisoners of war and civilians were forcibly transported to the Caribbean to work in indentured servitude on sugar plantations. Many of these people died, either on the plantations themselves or on the journey across the Atlantic.
The English Parliament passed the Act for the Settling of Ireland in August 1652, confiscating land from Irish Catholics and repopulating it with Protestant settlers. Irish Catholics were ordered to vacate their land and move west across the River Shannon in a traumatizing process (Ó Siochrú). Those who survived the journey struggled to rebuild their lives in unfamiliar places. Irish political leaders, prominent army officers, and Catholic clergy were sentenced to death, and their land was transferred to new owners.
Assessing the Cromwellian conquest in relation to international genocide law
Scholars argue that the NMA’s actions during the Cromwellian conquest amounted to genocide (Ó Siochrú; Canny). This section assesses the atrocities in relation to the Genocide Convention and genocide case law. This section is not arguing that the United Kingdom (UK) should be held legally liable for the actions of the NMA almost four centuries ago. Rather, it is using the Convention and case law as a retrospective analytical framework to determine whether the atrocities of the Cromwellian conquest can be considered a genocide in the context of modern international law.
Article II of the Genocide Convention states that genocide involves
1) killing members of a group; 2) causing serious bodily or mental harm to members of the group; 3) deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; 4) imposing measures intended to prevent births within the group; 5) forcibly transferring children of the group to another group.
These acts must be committed “with intent to destroy, in whole or in part, a national, ethnical, racial or religious group.”
The evidence relayed above shows that the NMA committed three of these acts. The NMA killed members of the Irish Catholic group at Drogheda and Wexford and again later under collective punishment policies. The NMA/Commonwealth of England caused serious harm to the Irish Catholics and inflicted conditions of life bringing about their physical destruction by creating a man-made famine, forcibly deporting Irish Catholics to plantations in the Caribbean, and forcing the mass displacement of the Act for the Settling of Ireland. Having established this, the question is now whether these were committed with a specific genocidal intent or dolus specialis.
Genocidal intent is difficult to prove without direct evidence indicating that a genocide was planned. However, Prosecutor vs Radovan Karadžkić ruled that
in the absence of direct evidence, genocidal intent may be inferred from a number of facts and circumstances, such as the general context, the perpetration of other culpable acts systematically directed against the same group, the scale of atrocities committed, the systematic targeting of victims on account of their membership in a particular group, the repetition of destructive and discriminatory acts, or the existence of a plan or policy.
The general context in which the conquest occurred shows genocidal attitudes towards Irish Catholics. Discriminatory rhetoric from English authorities and public figures was common during this period, becoming more dehumanizing in the aftermath of the 1641 rebellion and associated killings of Protestant settlers. Irish Catholics were described as “evil affected,” “reptilia,” and “inhumane, blood-sucking Tygers” (Ó Siochrú 63 and 168-169). A pamphlet published in the 1640s called for the Commonwealth of England to “warrantably and righteously endeavour the extirpation of them” (Ó Siochrú 63). In Prosecutor vs Ferdinand Nahimana, publishing dehumanizing statements such as these was ruled to constitute incitement to genocide.
The scale of the atrocities committed by the NMA in Ireland certainly indicates genocidal intent as the Irish Catholic population was, in part, destroyed. Different estimates have stated that the conquest caused the population of Ireland to fall by between 20% and 40%. This means that a total of 200,000-400,000 Irish Catholics were either killed, died due to man-made famine or associated diseases, or were deported to the Caribbean plantations where the death rate was high.
The repetition of destructive and discriminatory acts is also evident in the Cromwellian conquest. Having already committed a massacre at Drogheda, the NMA committed a further massacre at Wexford. Moreover, the destruction of Irish Catholics wasn't limited to isolated massacres, but repeated over several years through collective punishment, forced transplantation, and man-made famine.
Regarding the existence of a genocidal plan or policy, in October 1644 the English Parliament declared the following order:
The Lords and Commons assembled in the Parliament of England do Declare, That no Quarter [mercy] shall be given hereafter to any Irishmen, nor to any Papists [Catholics] whatsoever born in Ireland, which shall be taken in Hostility against the Parliament… And therefore do Order and Ordain, That the Lord General, Lord Admiral, and all other Officers and Commanders both by Sea and Land, shall except all Irishmen, and all Papists born in Ireland out of all Capitulations, Agreements, or Compositions hereafter to be made with the Enemy; and shall upon the taking of every such Irishman or Papist born in Ireland as aforesaid, forthwith put every such Person to death.
There are complications in inferring genocidal intent from this order. In the cases of Bosnia vs Serbia and Croatia vs Serbia, the International Court of Justice (ICJ) ruled that to infer genocidal intent from circumstantial evidence, it must be the “only reasonable inference.” Hence, the presence of the NMA’s military objectives (mentioned in the introduction) could complicate the inference of genocidal intent. The order above specifically instructs the elimination of Irish Catholics who were “in hostility against the Parliament.” Therefore, it could be inferred that there existed a military objective to the NMA’s atrocities, rather than a purely genocidal one.
However, the correct interpretation of “only reasonable inference” is widely debated, due to a lack of clarification by the ICJ. Many assume it means that the presence of other non-genocidal objectives automatically rules out genocidal intent. This interpretation ignores rulings which clearly state that genocidal intent can coexist with other objectives, such as Prosecutor v. Goran Jelisic (paragraph 49) and Prosecutor vs Eliézer Niyitegeka (paragraph 52). Alternatively, a widely-held interpretation among legal scholars and human rights organizations is that “if the pattern of conduct can be fully explained by a non-genocidal intent, then the standard of proof is not satisfied. But if the pattern of conduct can be fully explained only by a combination of genocidal intent and non-genocidal intent, then the standard of proof is satisfied.”
While military objectives existed in the Cromwellian conquest, this cannot fully explain the NMA’s pattern of conduct. This report holds that the deliberate targeting of Catholic clergy, the creation of a man-made famine, and the mass forced population transfer cannot be explained by military reasoning, and that the atrocities of the Cromwellian conquest “can be fully explained only by a combination of genocidal intent and non-genocidal intent.” This, combined with the above circumstantial evidence of the general context, scale of the atrocities, and the repetition of destructive and discriminatory acts, means it can be inferred that the NMA, under instruction from the English Parliament, intended to, and in fact succeeded, in committing acts that destroyed in part the Irish Catholic population.
This report is therefore satisfied that, under the Genocide Convention and modern genocide case law, the Cromwellian conquest of Ireland can be considered a genocide.
Conclusion
The memory of the Cromwellian conquest varies between Ireland and the UK. Cromwell is considered a monster in Ireland, yet he has a statue outside Westminster. The historical debate around Cromwell is unlikely to be settled anytime soon. The conclusion of this report, however, is that the NMA, both under Cromwell and his successors, committed a genocide of Irish Catholics.
Works Cited which cannot be hyperlinked
Canny, Nicholas. Making Ireland British, 1580-1650. 1 ed., Oxford, Oxford University Press, 2001.
---. “The English conquest of Ireland, c.1530–c.1650.” The Cambridge World History of Genocide, edited by
Ned Blackhawk, et al., 1 ed., vol. 2, Cambridge University Press, 2023, pp. 139- 162. 3 vols.
Morrill, John. “Rewriting Cromwell: A Case of Deafening Silences.” Canadian Journal of History, vol. 38, no. 3,
2003, pp. 553-578.
Ó Siochrú, Micheál. “Extirpation and Annihilation in Cromwellian Ireland.” The Cambridge World History of
Genocide, edited by Ned Blackhawk, et al., 1 ed., vol. 2, Cambridge University Press, 2023, pp. 163-185. 3 vols.
---. God's Executioner: Oliver Cromwell and the Conquest of Ireland. 1 ed., London, Faber & Faber, 2008.
