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May 14, 2026

Turning Tactical Victories into Strategic Success: Counterinsurgency in the Irish Civil War, 1922–23

Gareth Prendergast and John A. Nagl
©2026 Gareth Prendergast and John A. Nagl

ABSTRACT: The fundamentals the Irish National Army used in the Irish Civil War (1922–23) are a model for the successful application of a classic counterinsurgency which, if understood earlier, could have made a difference in the United States’ most recent wars in Iraq and Afghanistan. The Irish Civil War has not been examined in-depth through the lens of modern counterinsurgency doctrine. This article draws on military history and recent counterinsurgency doctrines to provide US policymakers and military practitioners practical guidance for how counterinsurgent forces can foster trust and use appropriate tactics that lead to strategic success.

Keywords: counterinsurgency, Ireland, Irish Civil War, military strategy, treaty

 

After two decades of unsuccessful counterinsurgent efforts in the Middle East, the US military is again preparing for great-power conflict, as it did in the wake of its last defeat in the Vietnam War.1 The causes of the United States’ defeat in the Afghanistan War will be studied for decades to come. Chief among these considerations must be the question of how to conduct counterinsurgency successfully—a problem recently troubling US ally Israel in the Israel-Hamas War.2 With numerous politicians and strategic thinkers championing this pivot to great-power conflict, the relevance of traditional best practices in nonconventional warfare remains particularly perilous and secluded. Thus, the conduct of successful counterinsurgencies will remain contentious, outmoded, unpopular, and on the margins, despite the publications of US Army and US Marine Corps counterinsurgency doctrines in 2006 and 2014.3

Success in Counterinsurgency

The successful prosecution of a counterinsurgent campaign is still a relevant and important part of phase-four warfare because it enables the transition from chaos or crisis into stability. Counterinsurgency must encompass a whole-of-society approach in which governmental legitimacy and popular support are crucial, along with the restoration of essential services and security. Soft, humanitarian efforts designed to win hearts and minds and isolate the insurgents from their support base are still a critical part of the transitional phase of warfare. After the lessons of the Iraq War and the Afghanistan War, modern theorists recently suggested efforts to win hearts and minds must be augmented by hard, kinetic power. Jacqueline L. Hazelton argues the approach that succeeds most in counterinsurgency is “uglier, costlier in lives, more remote from moral and ethical considerations, and far less ambitious than what the United States and its partners are attempting in trying to build and reform the political systems in so-called weak states and ungoverned spaces.”4 The authors of this article agree with Hazelton, particularly with respect to ungoverned spaces, where a sharper edge is required to bring control and security. Within the insurgent safe havens and ungoverned spaces, realistic actions are called for, especially during the initial clearance and conventional phase of a counterinsurgent campaign. Success in counterinsurgency should thus be defined as the “marginalization of the insurgents to the point at which they are destroyed, co-opted, or reduced to irrelevance in numbers and capability.”5 Colin S. Gray remarked that government forces must be steadfast and resolute in their conduct because half-hearted repression executed by self-doubting people does not work, though Frank Ledwidge issues a caveat by noting such force must be applied within a coherent and solid strategic framework, against the backdrop of a firmly understood end state.6

Using the Irish Civil War as a case study, this article contends, after the Irish National Army’s initial conventional and clearance successes during the summer months of 1922, the newly constituted Irish Free State successfully isolated and defeated the antitreaty Irish Republican Army (IRA), confining its activities to inaccessible strongholds and ungoverned spaces.7

The recently published book by Irish Army officer Gareth Prendergast agrees with, expands on, and joins the assertions of these modern theorists (Hazelton and Ledwidge).8 With important lessons for academics and practitioners, Prendergast’s detailed and comprehensive study of the Irish Civil War remedies the gap in the public understanding of an interesting and understudied effort to defeat an insurgency. While reading the book, veterans and students of the Iraq War and the Afghanistan War will recognize the tactics and strategies both sides employed during the Irish Civil War. One hundred years ago, Irish insurgents sent night letters, intimidated local construction firms, attacked key essential services, and terrorized the newly established civic police force. In response, the Irish Free State conducted key leader engagements, froze illicit bank accounts, secured local fairs and markets, and rebuilt key infrastructure. Whereas one may argue the US military does not intuitively have much to learn from this understudied conflict, this article takes the opposite tack, arguing that the principles and fundamentals the Irish National Army adopted are an excellent example of how to conduct a successful counterinsurgency which, if understood earlier, could have made a difference in the most recent American wars.

Background

The Irish Free State was forged in the flames of a bitter civil war fought between June 28, 1922, and May 24, 1923. Prior to the Irish Civil War, the Irish struggle against the British took on a political facade during the Home Rule crisis of 1913–14. Home Rule meant self-governance for Ireland within the British Empire, barring foreign affairs and defense. Violence and blood sacrifice, however, brutally replaced and superseded the arguments of constitutional politics during the short-lived Easter Rising of 1916. When World War I ended in November 1918, a full war of independence brought Ireland into a conflict with the British from January 1919 to summer 1921. In June 1922, the Irish Civil War started because of the disputed Anglo-Irish Treaty, which the Irish signed with the British authorities. The fighting lasted less than a year. This internecine struggle was different from the previous fight against the British, however, because it was no longer a noble struggle against a foreign, occupying power. This struggle was mean and base, as Irish volunteers fought against each other in an internal struggle over what a newly independent Ireland should look like.9 During this turbulent period, from Home Rule disputes to civil war, Ireland was transformed from an important part of the British Empire into a divided island. One portion in the north remained within the United Kingdom and the rest became a nascent Irish Free State. Ultimately, the civil war was fought over whether Ireland was to be a full republic or a realistic Irish Free State with notions of future independence. The protreaty side, led by Michael Collins, wanted a pragmatic deal to build on, taking the advantages it could get in the hope of creating an independent state later. The antitreaty elements of the Irish Republican Army, influenced mainly by Éamon de Valera, wanted to stay loyal to the pursuit of an immediate Irish republic.10 As the IRA leader Ernie O’Malley stated during the treaty debates, “How often had we vowed, as we sat around the turf fires, or as we tramped with squelching feet . . . that we, in our generation would finish the fight.”11

Collins and the protreaty side considered the treaty a stepping stone to full nationhood. The antitreaty—or republican—elements of the Irish Republican Army, however, enshrined in an oath of allegiance to the British monarchy, strongly objected to continued citizenship within the British Empire. Additionally, the partitioning of the island of Ireland—as six counties were to form Northern Ireland and remain in the United Kingdom—magnified the distaste of the republican elements.12

The Irish Civil War ensued after a house of the Irish parliament (Dáil) ratified the treaty. Brother fought brother as the young and idealistic leadership that spearheaded the fight for independence against the British decimated itself in a brutal year of internal violence. This struggle differed from the previous fight against the British, and it left a bitter taste for decades and a vacuum at the top, which the newly established Irish Free State would find difficult to fill.13

In a popular textbook F. S. L. Lyons wrote 50 years after the end of hostilities, he referred to the war as “burned so deep into the heart and mind of Ireland that it is not yet possible for the historian to approach it with the detailed knowledge or the objectivity which it deserves.”14 Now, more than 100 years after the end of fighting, the counterinsurgent strategy of the Irish National Army during this bitter campaign and the strategic successes this strategy produced must be comprehended and examined in detail.

Starting on June 28, 1922, the initial fighting in the Irish Civil War took place in Dublin, when Irish soldiers, dressed in the new uniform of the Irish National Army, shelled their former IRA colleagues who had illegally occupied the Four Courts (the headquarters of the Irish judicial system) in Dublin. After several weeks of fighting, Dublin was secured and most of the antitreaty IRA volunteers withdrew from the capital city and started to reinforce their strongholds in the south and west of Ireland. Dublin and the remaining east soon fell into the Irish Free State’s control, giving the Irish Free State a major advantage, as it secured the support of the hierarchy of Roman Catholicism, the banking sector, and the national newspapers for the newly forming government. The ensuing clearance operations to the south and west meant the Irish Free State had to use conventional tactics to control and secure the entirety of the new Irish Free State. As the summer’s conventional fighting transitioned into an unconventional winter struggle, the Irish Free State quickly learned several lessons, which eventually brought the IRA insurgency to an abrupt end. These lessons formulated the counterinsurgent methodology of the Irish National Army and formulate the chapters in Prendergast’s book.

Counterinsurgent Methodology of the Irish Free State

The methodology the Irish Free State adopted to end the fighting and substantially defeat the Irish Republican Army can be broken down into the following lessons learned.

The Benefits of Locally Recruited Soldiers

The Irish National Army grew from an initial force of 8,000 personnel at the start of the conflict to 55,000 personnel by the end of the fighting. Most of these fighters came from the localities they were recruited to defend. Nearly 50 percent of these recruits had previously gained military experience and training through fighting with the British Army during World War I. As the fighting moved south and west, the Irish Free State captured additional territory from the antitreaty Irish Republican Army, enabling the increased recruitment of local soldiers into the Irish National Army. These locally recruited soldiers had the advantage of preferential access to information since they were operating in areas where they lived and among known populations.15 When specialized forces support local forces, results are significantly enhanced, in the recent Iraq War as much as in Ireland 100 years ago.16 For example, in Waterford, a town in southeast Ireland, Lieutenant Colonel Patrick Paul (a native son and a former British Army artillery officer during World War I) proved a remarkable force multiplier for the Irish Free State. The combination of Paul’s local knowledge and his World War I gunnery expertise enabled the Irish National Army to use similar soldiers to hold, compel, and exert tremendous pressure on the Irish Republican Army.17 Seeing these obvious benefits, Paul urged the recruitment of local men with World War I experience, like himself, to fill the knowledge and experience vacuum in the original Irish National Army.18 Similarly, Irish Free State Major General Emmet Dalton (also a World War I veteran), realized the benefit of local troops, observing most of his newly recruited soldiers in Cork were local and had previous military experience.19

The British indirectly provided combat-experienced fighters to the Irish Free State and developed a strategy where the British directly supported the new Irish National Army with rifles, machine guns, artillery pieces, ammunition, armored vehicles, ships, and aircraft. These weapons of war would have remained empty capabilities if the Irish Free State had not recruited the technical expertise needed to operate them. Through an active recruitment policy, in conjunction with the British Legion of retired veterans, the Irish Free State government attained the services of nearly 30,000 former British Army servicemen living in Ireland, who provided the much-needed technical expertise.20 Local soldiers were especially necessary to hold the terrain after clearance operations; therefore, such soldiers often took extra rifles when conducting operations. After the initial fighting and capturing terrain from the antitreaty Irish Republican Army, the Irish National Army forces rapidly expanded their strength by recruiting and arming local volunteers.

In addition to the Irish veterans of World War I, specialized troops were organized to support the local Irish Free State garrisons throughout the country. These organized troops included members of the newly formed Irish National Army intelligence corps, the railway protection corps, and countercolumns—specialized forces (maybe a precursor to special forces), which comprised experienced soldiers who would link up with local soldiers, especially in sweep-and-search operations. Locally recruited soldiers would normally occupy the outer cordons, allowing the more capable and battle-hardened countercolumns to operate in the interior to search for and destroy IRA flying columns.21 This tactic effectively harassed and exhausted the IRA insurgent fighters. Irish National Army intelligence officers would also typically attend the searches and sweeps to report on casualty rates, infrastructural damage, and other IRA activities. Even after the fighting, continued intelligence reports reflected the importance the Irish Free State placed on the restoration of essential infrastructure.22 By the end of the Irish Civil War, the Irish National Army could mass forces, sometimes using more than 2,000 local and specialized troops to cover more than 1,000 square kilometers of difficult terrain.23

A major benefit afforded to the Irish Free State in this contentious civil war was locally recruited soldiers’ understandings of how local networks fight.24 Insurgent networks tend to be driven by local issues and alliances. Whereas this reality may have been more difficult for the British to understand during the previous Irish War of Independence, Irish soldiers recruited locally during the Irish Civil War had better insight.25 Therefore, the antitreaty IRA networks, which were difficult for the British to infiltrate, were particularly vulnerable to the Irish Free State’s use of local forces, which are familiar with the cause of an insurrection in a particular area and know what is required on the ground. When specialized units support the local soldiers, the soldiers are more effective than outside troops in finding out how and where the insurgent networks recruit, train, operate, and sustain themselves.26

Peter Hart, a Canadian historian, observes the most important bonds holding the antitreaty IRA volunteers together during the Irish Civil War were those of family and neighborhood.27 By the end of war, Irish Free State personnel knew most IRA networks, families, and vulnerabilities—including the devastating effects of the Roman Catholic Church’s censure.28 As a result of the Irish Free State transforming these weaknesses into devastating vulnerabilities, republicans believed the once-powerful Irish Republican Army would “not have a man left owing to the great number of arrests and casualties” stemming from the information civilians supplied to the local police and Irish National Army troops.29

Establishing Civil Control and Civil Security

The insurgent’s goal is to create a climate of insecurity and compel the forces of order to retire into their most easily defensible areas.30 But security cannot be provided from large, isolated bases or only during daylight hours because it must be all-encompassing. Troops must live among and protect the population until the population can protect itself.31 Providing a safe environment makes delivering services to citizens easier and helps citizens share crucial information.32 Community inhabitants will identify the insurgents in their midst only if they know they will survive the experience.33

The Irish National Army bases established across the towns and villages of Ireland proved highly successful in garnering information to subdue the antitreaty Irish Republican Army and in fostering good relations with the local people.34 By the end of the Irish Civil War, most army reports referred to the steadily improving relationship between the Irish National Army and the people.35

Additionally, the Civic Guard (the newly formed Irish civic police force) was deployed to unoccupied, formerly British police stations throughout the country, sometimes without the assistance of experienced police personnel or even manuals.36 The government realized the dangers but insisted on putting the unarmed guards into communities in hostile areas: “You may be murdered, your barracks burned, your uniform taken off you, but you must carry on and bring peace to the people.”37 Thus, embedded in the local communities, the Civic Guard became a noticeable security presence and a vital building block for the new Irish Free State.38 The Irish Republican Army had blinded the British colonial police, the Royal Irish Constabulary, during the previous Irish War of Independence.39 But during the Irish Civil War, circumstances were different because the new Irish Civic Guard had preferential access to information since its members were operating in areas they knew intimately.40 By providing local policing, the Irish Free State also provided an easier and more accessible way for the local populations to impart information and, because of this resourcefulness, achieved dramatic results. Irish Free State intelligence and after-action reviews claimed that, by 1923, the IRA supporters left fighting were for the most part “men who have been led astray and who really did not know what they were doing. They simply followed certain leaders.”41

An overarching strategy for all counterinsurgent operations is to recognize that the people who matter most are the ones on the margins because they constitute the target audience for information sharing and information operations.42 Providing all-round security separates the population (especially marginalized members of the population) from the insurgents and the underlying causes of the conflict. This indirect approach to defeating an insurgency is usually more effective than a direct approach over the long term.43 As the Irish Civil War concluded, even the most stridently republican populations became more accepting of the Irish National Army.

Mobile columns supported and supplemented the Irish National Army’s policy of living among the population it wanted to protect. As the Irish National Army moved into the more remote parts of the south and west, its mobile columns in light armored vehicles brought the fight to the enemy, rounding up antitreaty fighters in their safe areas, seizing arms, and inflicting casualties.44 These columns reduced the flow of resources to the insurgency and eventually broke the IRA fighters’ wills and squelched the IRA’s ability to continue to fight.45 As the war continued, additional mobility—especially armored mobility provided by the British government—brought flexibility to the Irish Free State forces.

Mobility and freedom of movement allowed the army to keep its lines of communication open and keep the Irish Republican Army on its back foot. This reality undoubtedly contributed to the Irish National Army’s domination of key terrain and the suppression of IRA activities.46

Irish Free State harassment and compellence operations corresponded with the concept that it must apply force within a coherent and solid strategic framework, against the background of a clear, realistic political context and a firmly understood end state.47 The kinetic force the Irish National Army applied throughout the fighting coincided and coexisted with ongoing good governance efforts at the national and local levels. These complementary processes may have been ad hoc at first. But when properly coordinated, the processes led to the defeat of the Irish Republican Army by summer 1923.

The Advantages of Good Governance

The Irish Free State government instinctively understood that good governance fills the vacuum created by ungoverned spaces. Thus, the primary tasks involved with governing at the national and local levels were performed following the same general organization and procedures as before the Irish Civil War.48 In January 1923, Irish Free State Minister of Justice Kevin Christopher O’Higgins issued a memorandum declaring a powerful truth: “[T]he Government is simply a Committee with a mandate to make certain conditions prevail, to make life and property safe, and to vindicate the legal rights of their fellow citizens.”49

The Irish Free State understood a functioning government must be financially viable, uphold a common set of rules, and operate in a stable environment nationally and locally. Government policies were connected with and directly affected regional activity, especially in Munster, and governance was pushed down to the local level to stabilize the new Irish state. Good governance needs a democratic framework, with opposing political parties. According to Hazelton, good governance must provide political, economic, and social reforms that meet the needs of the population, gain its support, and ensure these reforms reduce the grievances fueling the insurgency.50 Effective, legitimate governance is transparent, accountable, and incorporates public participation. The activities of good governance are among the most important in ensuring lasting stability.51 In the Ireland of 1922–23, O’Higgins argued, “nothing could be more disastrous than the virtual isolation of the government. A responsible government meant one that had to answer to the people.”52 Through a remarkable mixture of force and cajoling, the Irish Free State managed to use the previous British civil service to help stabilize the country. Inheriting civil servants from the former British administration had many advantages, and the civil servants’ distance from the revolutionary state-building process ensured stability and continuity.53 More than 21,000 civil servants who opted to transfer to the Irish Free State were fully trained, professional, and theoretically apolitical (and, by 1922, predominantly Irish by birth), which was a significant advantage.54 Ireland had been bequeathed a complete central and local government apparatus.55 This development was a significant boost to the nascent state, guaranteeing the presence of trained administrators who were removed from the complex ideological strains and loyalties of a civil war.56 Even more remarkable is that the state’s leadership on both sides of the Irish Civil War later reconciled. Ten years later, the losing side in the civil war followed the wishes of the electorate and formed a democratic government.57

The Importance of Restoring Essential Services, the Economy, and Information Operations

The Irish Free State had a clear policy from the outset of the Irish Civil War. The Irish Free State wanted to create a democratic country underpinned by functioning governance at the local and national levels with the support of the new Irish National Army. The antitreaty Irish Republican Army had no viable political alternative.58 By the end of the Irish Civil War, the Irish Republican Army’s sole policy was to make an Irish Free State government impossible. This reality translated into wholesale destruction during the Irish Civil War, which destroyed scarce infrastructural resources and delayed development.59 By taking those actions, the Irish Republican Army eventually lost the support of the Irish population—and ultimately the war. As the Irish Free State government protected and repaired essential infrastructure (especially in Munster and the south) the Irish Free State slowly gained the upper hand in the battle for public support. Principally, the Irish Free State government understood the psychological effect of restoring and protecting essential services because such restoration allowed resumption of trade, helped restore normal life, and improved living standards. Moreover, entities such as the Railway and Salvage Protection corps brought freedom of movement for both the military and civilians.

As key roads, railways, and communication lines were resuscitated, so too was the economy. The process swung public opinion behind the government and marginalized the antitreaty Irish Republican Army.60 The Irish Republican Army left a trail of infrastructural destruction throughout County Cork county and the larger Munster region and caused the inhabitants much hardship by commandeering supplies for its survival and siphoning off revenues wherever possible. The Irish Free State reacted by repairing, restoring, and protecting essential infrastructure and offering better services to the population. In the process, the Irish Free State was able to win over the neutral majority of the population and erode the IRA cause.61 The formation of the Railway Protection, Repair and Maintenance Corps also proved how flexible, adaptable, and cognizant the Irish Free State government was. Cabinet papers from September 1922 proposed engaging 1,200 idle civilian railway employees in police or military work to help maintain rail services.62 The Irish National Army quickly recruited these workers into specialized units, which proved enormously helpful in restoring and protecting essential services.

The Irish Free State also used Roman Catholicism and the national press as vital tools to conduct information operations. The Roman Catholic Church came out strongly against the antitreaty Irish Republican Army in Ireland, alleging young minds were being poisoned by its false principles. A bishop’s pastoral letter issued by the Roman Catholic Church in October 1922 condemned the actions of the antitreaty Irish Republican Army, stating its killings of Irish National Army soldiers were murders.63 Whereas the disapprobation had a serious effect on IRA volunteers, the social ostracism engendered by church and state had a deeper effect on IRA volunteers’ partners and parents.64 In addition to religious condemnation, the republican narrative received a pasting from the press. As the Irish National Army gradually gained control across the country, mainstream newspapers reached individuals who had previously been fed solely republican ideology. The papers reported favorably on Irish Free State actions while challenging IRA activities, further damaging the insurgent cause. Corresponding with this information campaign at the tactical level, an Irish National Army report explains further how these policies had beneficial strategic effects. Increasingly, “fairs and markets are presently being conducted in the old style . . . business in small towns is improving and when the Government schemes for employment are put into effect a general ‘buck-up’ in all business is confidently anticipated.”65

Additionally, the Irish Free State bolstered its presence, posture, and profile through parades and shows of force, which paid off. The general survey for the period ending October 17, 1923, noted civilians “are at last beginning to realise that the soldiers of the [Irish National Army] are the friends and protectors of the people rather than the representatives of military tyranny as they were formerly led to believe.”66 The survey also noted, “from all parts come very favourable reports as to the attitude of the people generally towards our troops.”67 Measures of success taken through surveys indicated how the people in Ireland came to favor the Irish National Army because of its economic policies. This development was an important strategic enabler for the Irish Free State and supported the overall Irish Free State policy and strategy of strengthening governance, democracy, and the rule of law.68

The Ability to Become an Adaptive Learning Organization

A successful counterinsurgent force is built on an adaptive learning organization that can react quickly to unexpected circumstances, adjust its methods of operating accordingly, and thereby facilitate compellence and good governance simultaneously.69 The ability to learn and adapt is demonstrated in the structure of a military organization and in its willingness to develop new organizations to deal with changing situations.70

Irish National Army leadership quickly realized Irish-born World War I veterans would be a vital cog in the combat effectiveness and training expertise of a growing army. After the Irish Republican Army resumed guerrilla warfare and launched a successful fight in autumn 1922, the Irish Free State started to lose the momentum it had initially gained during the conventional phases of the war. Reviewing the situation, the Irish National Army Chief of Staff Richard James Mulcahy suggested to his fellow general, Seán MacMahon, despite their widespread unpopularity, former British Army officers should be enlisted onto a technical committee so “their ideas would . . . provide a base line against which we would compare what we’re actually doing ourselves.”71 Because of the findings of the technical committee, the Irish National Army infantry forces were battle grouped and countercolumns were formed. Training establishments were established for key combat support capabilities, including an artillery and armor school.72

Flexibility, doctrine, and military education allow a military force to make transitions in a complex environment. As General Michael Joseph Costello said at an army inquiry after the Irish Civil War, every officer admitted the army had made extraordinary improvements between December 1922 and April 1923, many because of a reorganization and restructuring that occurred in January.73 Mulcahy had a clear strategic vision for the type of organization he wanted to establish; namely, a permanent and centrally controlled defense force, which would take its orders from the Irish Free State government.74 Within the organization of the Irish National Army, the creation of district or regional commands—at least in principle—enabled the Irish Free State to develop a strategic plan of action that offered a vital advantage over its IRA adversaries.75

The newly adopted leadership format, the streamlining of command and control, and the breakdown of territory for Irish National Army units allowed battle groups to operate and cooperate cohesively and effectively. These changes also gave the infantry units the elasticity and flexibility Mulcahy had advocated as early as August 1922.76 By deploying and reinforcing its forces throughout the country, the army increased its mobility, harassed the Irish Republican Army, and learned from its mistakes. As a learning organization, the Irish Free State reconstituted the army and brought the fight back to the antitreaty Irish Republican Army with improved tactics and strategy.

Turning Tactical Victories into Strategic Successes

Fundamentally, the Irish Free State won the Irish Civil War because it turned tactical victories into strategic successes. The Irish Free State won during the hold and build phases, when the Irish National Army capitalized on its initial, conventional victories by holding key terrain and reinforcing those victories. As the war progressed, the Irish National Army built upon its momentum by rebuilding Irish society and essential services, thus engendering the population’s support for the government.

By May 1923, Irish National Army reports pointed to undeniable facts. In almost every command area, the Irish Republican Army was “absolutely broken or else hampered in such a way as to render it almost impossible for them to carry out any major operation. The large numbers of arrests and captures of dumps during the week is evidence of the effective manner in which the troops are clearing the parts of the country that yet call for attention.”77

Impelled by the many setbacks, antitreaty republican cabinet members met at an army council on May 13 and May 14 to discuss their options. From a military point of view, the republican effort was beyond hope. But with antitreaty IRA peace proposals rejected, the two sides could not agree on terms for the cessation of hostilities. The state slipped into an uneasy peace.78 Eventually Frank Aiken, who had replaced Liam Lynch as IRA chief of staff, suspended any offensives. On May 24, 1923, Aiken ordered the Irish Republican Army to dump arms.79 A bitter civil war had ended.

History Does Not Repeat Itself, but It Certainly Rhymes

To the neutral observer, the Irish National Army seemingly won the Irish Civil War because of superior numbers and equipment. But those advantages only came later in the conflict and the army could easily have squandered its advantages by neglecting the support of the population. Heavy-handed tactics, disregard for public opinion, clumsy operations resulting in excessive civilian damage, illegitimate governance, an absence of local security and a lack of essential services, errors of judgment, and a failure of common sense have proven devastating to counterinsurgent campaigns throughout history. When military leaders and their armies fail to capitalize on initial support from the local population, they waste their original advantage. The forces of liberation can often become an army of occupation because of poor planning and a lack of cultural awareness: a problem Irish National Army leaders faced during the Irish Civil War.

The leadership of the US Army also faced this problem during the Iraq War. In fact, a better description cannot be written of the mistakes the US Army made in the initial phases of its occupation of Iraq in 2003, proving (not for the first time) if history does not repeat itself, it certainly rhymes. Had greater awareness of counterinsurgent strategy existed in 2003—and, more importantly, had the American national security team understood the lessons of counterinsurgent strategy—history might have turned out differently.

The path the Irish National Army followed to defeat the antitreaty Irish Republican Army is also a road map that could have made the Iraq War shorter and less costly for Americans, their allies, and the people of Iraq. The very title of Prendergast’s new book covers the most important realization the United States stumbled onto years into the bloody Iraq War: Sweep-and-clear operations are useless unless the counterinsurgent government leaves forces behind to hold the area that has been cleared of insurgents and then builds a better government and future for the people of the afflicted region. Enormous wisdom is available in the words clear, hold, and build. The fact that those techniques worked in Dublin and Cork in much the same ways they did a century later in Baghdad and Ramadi indicates counterinsurgency doctrine may transcend culture, race, language, and religion. Creating regional security and then building a government that meets the needs of the people is a strategy for all armies to ponder, in as many cases as they can muster.

Conclusion

Counterinsurgent forces should not commute to work. Forces embedded within, and living among, local communities become intelligence collectors and analysts. Those forces are the holders and builders—the keys to victory.80 By fostering trust and recruiting locally, the Irish Free State weakened support for the antitreaty Irish Republican Army, enhanced its own standing, and improved its ability to obtain useable information. As the Irish Free State untangled IRA support networks and undermined its cause, restored essential infrastructure, rebuilt the economy, and provided better governance, the Irish Free State bridged the gap between local victories and overall strategic success.

This development was the difference between winning the villages of Ireland tactically and winning a counterinsurgent war strategically. Although the Irish National Army made mistakes throughout the campaign, by being adaptive and flexible as a learning organization, it was able to take the kinetic fight to the Irish Republican Army, harassing its fighters and overwhelming their safe havens.

How fully the hearts and minds of the Irish population were won cannot be measured. By the end of the fighting, however, Irish Free State reports recorded positive attitudes toward the Irish National Army.81 The neutral majority was won over when essential services and infrastructure were rebuilt after years of conflict and neglect. At the heart of any counterinsurgent campaign lies a fundamental requirement: Undermine the insurgent cause by offering a more attractive alternative. By 1923, after 10 years of turmoil, most people in Ireland had formed the pragmatic perception that the Irish Free State government offered a better deal than the antitreaty elements of the Irish Republican Army.82

 
 

Gareth Prendergast
Dr. Gareth Prendergast is a serving colonel in the Irish Army and the author of Clear-Hold-Build: How the Free State Won the Irish Civil War (Eastwood Books, 2025).

John A. Nagl
Dr. John A. Nagl is the General John J. Pershing Professor of Warfighting Studies in the Department of Military Strategy, Planning, and Operations at the US Army War College.

 
 

Endnotes

  1. 1. John A. Nagl, “Why America’s Army Can’t Win America’s Wars,” Parameters 52, no. 3 (Autumn 2022), https://press.armywarcollege.edu/parameters/vol52/iss3/3/.
  2. 2. deRaismes Combes and John Nagl, “A Viable Solution for Mideast Peace? Lessons from the U.S. Misadventures in Iraq and Afghanistan,” Horizons: Journal of International Relations and Sustainable Development 26 (Spring 2024).
  3. 3. Gian Gentile, “Ukraine, Gaza, and the U.S. Army’s Counterinsurgency Legacy,” War Room, December 21, 2023, https://warroom.armywarcollege.edu/articles/learning-lessons-4/. For a rebuttal, see John Nagl and Paul Yingling, “ ‘A Complex and Sophisticated Strategy’: Counterinsurgency in the Words of a Critic,” War Room, February 1, 2024, https://warroom.armywarcollege.edu/articles/complex-and-sophisticated/.
  4. 4. Jacqueline L. Hazelton, Bullets Not Ballots: Success in Counterinsurgency Warfare (Cornell University Press, 2021), 2.
  5. 5. US Government Interagency Counterinsurgency Initiative, U.S. Government Counterinsurgency Guide (Department of State Bureau of Political-Military Affairs, January 2009), 4, https://2009-2017.state.gov/documents/organization/119629.pdf.
  6. 6. Colin S. Gray, Another Bloody Century: Future Warfare (Phoenix Press, 2007), 222; and Frank Ledwidge, Losing Small Wars: British Military Failure in the 9/11 Wars, 2nd ed. (Yale University Press, 2017), 186.
  7. 7. The Irish National Army was formed in early 1922 from the protreaty sections of the Irish Republican Army. This Irish National Army was formed to act as a new army for the newly formed Irish Free State and to act as defenders of the Anglo-Irish Treaty, which the Irish signed with the British in December 1921 to end the Irish War of Independence.
  8. 8. Gareth Prendergast, Clear-Hold-Build: How the Free State Won the Irish Civil War (Eastwood Books, 2025).
  9. 9. Prendergast, Clear-Hold-Build, xvii.
  10. 10. De Róiste Diaries, 19 October 1922, U271/A/46, Cork City and County Archives, Ireland.
  11. 11. Ernie O’Malley, The Singing Flame (Anvil Books, 1936; repr., Mercier Press, 2012), 61.
  12. 12. For the conditions of the treaty and the republican response, see John McColgan, British Policy and the Irish Administration, 1920–22 (George Allen and Unwin, 1983), 90; and John Borgonovo, The Battle for Cork: July–August 1922 (Mercier Press, 2011), 23.
  13. 13. Prendergast, Clear-Hold-Build, 209.
  14. 14. F. S. L. Lyons, Ireland Since the Famine (Scribner, 1971), 460.
  15. 15. Eli Berman et al., Small Wars, Big Data: The Information Revolution in Modern Conflict (Princeton University Press, 2018), 273.
  16. 16. Berman et al., Small Wars, Big Data, 273.
  17. 17. Calton Younger, Ireland’s Civil War (Frederick Muller, 1968), 476.
  18. 18. Mulcahy to Collins, memorandum, 1991, P7/C/35, Richard Mulcahy Papers, University College Dublin Archives (UCDA).
  19. 19. Borgonovo, Battle for Cork, 31; and Michael Hopkinson, Green Against Green: The Irish Civil War (Gill Books, 2004), 239.
  20. 20. Prendergast, Clear-Hold-Build, 37.
  21. 21. Sean Lehane to Ernie O’Malley, October 15, 1922, in “No Surrender Here!,” The Civil War Papers of Ernie O’Malley, 1922–1924, ed. Cormac O’Malley and Anne Dolan (Lilliput Press, 2007), 282.
  22. 22. Free State Army Intelligence Report (Cork Command), 2 March 1924, IE/MA/S/12360, Military Archives of Ireland, Dublin.
  23. 23. National Army Report on Operations Carried Out in the West Cork and South Kerry Areas, April 29–May 5, 1923, D/T S3361, National Archives of Ireland (NAI), Dublin.
  24. 24. John Arquilla, “How Can French Encounters with Irregular Warfare in the 19th Century Inform COIN in Our Time?,” interview by Michael Few, Small Wars Journal, November 30, 2010, https://archive.smallwarsjournal.com/jrnl/art/interview-with-dr-john-arquilla.
  25. 25. Prendergast, Clear-Hold-Build, 10.
  26. 26. Prendergast, Clear-Hold-Build, 220.
  27. 27. Peter Hart, The I.R.A. and Its Enemies: Violence and Community in Cork, 1916–1923, 1st ed. (Oxford University Press, 1998), 209, 264.
  28. 28. W. H. Kautt, Arming the Irish Revolution: Gunrunning and Arms Smuggling, 1911–1922 (University Press of Kansas, 2021), 151–52.
  29. 29. 1st Southern Division Meeting, 26 February 1923, P7/B/89, Richard Mulcahy Papers, UCDA.
  30. 30. Roger Trinquier, Modern Warfare: A French View of Counterinsurgency (Pall Mall Press, 1964; repr., Praeger Security International, 2006), 45.
  31. 31. David Galula, Counterinsurgency Warfare: Theory and Practice (Praeger Security International, 1964), 57.
  32. 32. Berman et al., Small Wars, Big Data, 17.
  33. 33. John A. Nagl, Knife Fights: A Memoir of Modern War in Theory and Practice (Penguin Press, 2014), 130.
  34. 34. Galula, Counterinsurgency Warfare, 85.
  35. 35. National Army General Surveys of the Situation for Weeks Ending March 31, 1923, and April 7, 15, 21, and 28, 1923, D/T S3361, NAI, Dublin.
  36. 36. Brian McCarthy, “Untitled” (master’s thesis, University College Dublin, 1977), 1–7.
  37. 37. Editorial, Irish Independent, June 13, 1977.
  38. 38. Donal P. Corcoran, Freedom to Achieve Freedom: The Irish Free State 1922–1932 (Gill and Macmillan, 2013), 113.
  39. 39. Prendergast, Clear-Hold-Build, 199.
  40. 40. Berman et al., Small Wars, Big Data, 273.
  41. 41. National Army Report on Operations, April 29–May 5, 1923, NAI, Dublin.
  42. 42. Berman et al., Small Wars, Big Data, 321.
  43. 43. John A. Nagl, Learning to Eat Soup with a Knife: Counterinsurgency Lessons from Malaya and Vietnam (University of Chicago Press, 2005), 28.
  44. 44. Sean Boyne, Emmet Dalton: Somme Soldier, Irish General, Film Pioneer (Merrion Press, 2016), 246.
  45. 45. Hazelton, Bullets Not Ballots, 5.
  46. 46. Boyne, Emmet Dalton, 246.
  47. 47. Ledwidge, Losing Small Wars, 186.
  48. 48. Stationary Office, Final Report of the Commission of Inquiry into the Civil Service, 1932–35 (Stationery Office, n.d.), para. 8.
  49. 49. Memorandum by Kevin Christopher O’Higgins, January 11, 1923, P7b/96, Richard Mulcahy Papers, UCDA.
  50. 50. Hazelton, Bullets Not Ballots, 8; and Stephen T. Hosmer and Sibylle O. Crane, Counterinsurgency: A Symposium, April 16–20, 1962 (RAND Corporation, 1963), iv.
  51. 51. Headquarters, Department of the Army, Stability, Field Manual 3-07 (Headquarters, Department of the Army, June 2014); and Headquarters, Department of the Army, Counterinsurgency, Field Manual 3-24 (Headquarters, Department of the Army, 2006).
  52. 52. John M. Regan, “The Politics of Utopia: Party Organisation, Executive Autonomy and the New Administration,” in Ireland: The Politics of Independence, 1922–49, ed. Mike Cronin and John M. Regan (Palgrave Macmillan, 2000), 44.
  53. 53. Ronan Fanning, The Irish Department of Finance 1922–58 (Institute of Public Administration, 1978), 56–88.
  54. 54. Ronan Fanning, “Britain’s Legacy; Government and Administration,” in Ireland and Britain Since 1922, Irish Studies 5, ed. P. J. Drudy (Cambridge University Press, 1986), 51.
  55. 55. Sean Dooney, The Irish Civil Service (Mount Salus Press, 1976), 1.
  56. 56. Regan, “Politics of Utopia,” 33.
  57. 57. Brian Girvin, From Union to Union: Nationalism, Democracy and Religion in Ireland—Act of Union to EU (Gill and Macmillan, 2002), 63.
  58. 58. De Róiste Diaries, 19 October, 1922, U271/A/47, Cork City and County Archives, Ireland.
  59. 59. National Army Report for Week Ending January 21, 1923, P7/B/124, Richard Mulcahy Papers, UCDA.
  60. 60. Cork Chamber of Commerce, Cork Chamber of Commerce Annual Report 1922, MP 507 (Cork Chamber of Commerce, 1922).
  61. 61. Galula, Counterinsurgency Warfare, 53.
  62. 62. Minutes of the Cabinet Meeting of the Provisional Government, September 10, 1922, D/TSCH/1/1/1, NAI, Dublin.
  63. 63. Prendergast, Clear-Hold-Build, 148.
  64. 64. Hopkinson, Green Against Green, 239.
  65. 65. National Army Intelligence Report (Cork Command), February 2, 1924, IE/MA/S/12360, NAI, Dublin.
  66. 66. General Survey for the Period Ending October 17, 1923, IE/MA/CW/OPS/3/B, Military Archives of Ireland, Dublin.
  67. 67. General Survey, October 17, 1923, Military Archives of Ireland.
  68. 68. Prendergast, Clear-Hold-Build, 211.
  69. 69. Nagl, Knife Fights; and British Army, Design for Military Operations: The British Military Doctrine (Her Majesty’s Stationery Office, 1989), vii.
  70. 70. Nagl, Soup with a Knife.
  71. 71. Mulcahy to MacMahon, December 12, 1922, P7/B/153, Richard Mulcahy Papers, UCDA.
  72. 72. John P. Duggan, A History of the Irish Army (Gill and Macmillan, 1991), 109.
  73. 73. Costello at Army Inquiry, n.d., P7/C/25, Richard Mulcahy Papers, UCDA.
  74. 74. Eunan O’Halpin, Defending Ireland: The Irish State and Its Enemies Since 1922, 1st ed. (Oxford University Press, 1999), 16.
  75. 75. Charles Townshend, The Republic: The Fight for Irish Independence, 1918–1923 (Penguin Books, 2014), 421–22.
  76. 76. Mulcahy to MacEoin, August 14, 1922, P151/161/5, Seán MacEoin Papers, UCDA.
  77. 77. National Army Report for Week Ending May 26, 1923, P7/B/139, Richard Mulcahy Papers, UCDA.
  78. 78. Corcoran, Freedom to Achieve Freedom, 95.
  79. 79. Diarmaid Ferriter, Between Two Hells: The Irish Civil War (Profile Books, 2021), 118.
  80. 80. John A. Nagl, foreword to Counterinsurgency Warfare, by Galula, ix.
  81. 81. Prendergast, Clear-Hold-Build, 211.
  82. 82. Michael Crawshaw, The Evolution of British COIN, Joint Doctrine Publication 3-40 (Ministry of Defence, December 2012), para. 1.
 
 

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