New Great War Episode: The Bloody Climax Of The Anglo-Irish War

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It’s March 1921, and in the Irish countryside, an IRA ambush has killed a British Brigadier General. He is the highest-ranking British casualty so far, but his death is only one of many in the bloodiest period of the Anglo-Irish War:

The final months of 1920 saw important developments in the Irish War of Independence. IRA assassinations and ambushes attacks had shocked the British authorities, who reacted with more violence and imposed martial law in Ireland. Spring 1921 brought further escalation but only months later, events would force the British and Irish Republicans to the negotiation table. In this episode, we’ll take a look at the war in Ireland in the first half of 1921 and the truce that followed – and it all took place exactly 100 years ago.

After the infamous events of Bloody Sunday and the Kilmichael Ambush in late 1920, the British government decided to impose martial law. This was a step that British Commander in Ireland General Nevil Macready had been pushing for, but once it came it did not quite work out as planned.

For one thing, martial law was only declared in four counties, which were now known as the Martial Law Area, or MLA. It was eventually extended to all of Munster, but the majority of Ireland remained outside of the MLA. The British also disagreed about what martial law actually meant in practice, both in terms of its powers and purpose. Military men hoped it would give the army centralized control over the different British forces on the island. Dublin Castle official Mark Sturgis also recognized the infighting caused by the complicated British command structure:

“... if it is war [then] we must have a virtual Dictator… As it is we are a great, sprawling, jealous hydra-headed monster spending much of its time using one of its heads to abuse one or other of the others by minute, letter, telegram and good hard word of mouth.” (Townshend 226)

On the other hand, local police chiefs did not want strict central control, because they felt they needed the freedom to act as they saw fit against suspected IRA fighters and their supporters. Government officials in London tended to interpret martial law cautiously, and hoped that the threat of force would be enough to discourage Irishmen from joining the IRA. General Macready recognised these political restraints:

“There are various little points on which we have to give way to the politicians… [6th Division commander] Strickland will have to watch the police carefully, because certainly Prescott-Decie [the 6th Division police adviser] will think that martial law means he can kill anybody he sees walking along the road whose appearance may be distasteful to him… I fully realise the difficulty this partial application of martial law means, but the “Frocks” were firm not to impose it all over. We must begin slowly and I have no doubt we will be able to fit in a workable scheme as time goes on’. (Hopkinson p. 278)

Because of British conflicting interests and inconsistent decisions, martial law ended up achieving achieved little of what anyone wanted. Military courts, an important part of martial law, were consistently overruled by civilian courts of appeal. And official police reprisals against the population, which martial law permitted, alienated locals, liberal British politicians, and international opinion.

In addition to martial law, the British also tried political solutions to the Irish Question. In late December 1920, they passed the Government of Ireland Act, which planned for two Home Rule systems on the island: one for the North, and one for the rest. Ireland would have two self-governing parliaments, and would remain a part of the United Kingdom. But the Act satisfied no one: Irish Republicans wanted no less than full independence, and Unionists felt that Britain was abandoning them.

So in early 1921 the British were trying to defeat the IRA by force, but also introduce a long-term political solution in the form of Home Rule. Prime Minister Lloyd George proposed a truce to the IRA, and planned for Irish elections in May 1921. The IRA rejected the truce since they would have had to disarm, and Lloyd George now instructed General Macready to crush the republicans in 5 months.

Despite the setbacks of late 1920, Macready felt British forces in Ireland were up to the task of destroying the IRA. The British eventually sent 51 battalions of troops to Ireland, although most were understrength and the men inexperienced. The best British troops were kept in Britain to deal with a potential general strike.

The British had also learned some tactical lessons from previous disasters. Police and military patrols began varying their routes and patrol times to prevent ambushes. They also travelled in larger groups, often convoys that included armoured-plated troop transports and armoured cars. More of the machine gun-equipped Peerless and Rolls Royce were sent, bringing the total to 104 by March.

The most significant British adjustment was a shift in patrolling. Passive patrols were increasingly substituted for aggressive, multi-day drives into IRA-dominated territory. Aided by the better spring weather, these pushes were designed to break up IRA formations and find and destroy weapons caches. Meanwhile, smaller platoons would hunt down IRA leaders and organizers, either to arrest or kill them.

Despite these more effective British tactics, there were still problems. Discipline had improved over the winter, but it was still lacking, and morale was still low. Auxiliary Division Commander Frank Crozier resigned because of the unit’s disciplinary issues, and other commanders knew their men were under constant strain. There weren’t many places safe enough for the troops to rest. Macready even predicted the entire force would have to be replaced by October 1921, as he warned London:

“The Government [must] bear in mind the personal feelings of the tools they [are] using, [otherwise] those tools [will] break apart in their hands.” (Townshend 302)

So the British had made changes to their military and political approach in Ireland but were no closer to a solution in either area. The IRA had a series of victories in late 1920 that had weakened the British position, but in some ways it had become a victim of its own success.

IRA military victories and propaganda had led to a large spike in volunteers. By 1921, some IRA flying columns consisted of over 100 men, which meant they were becoming more difficult to use. Such large numbers were hard to arm, conceal, and train, and also increased the chances of security leaks or British infiltration. Many of the new members lacked the experience and resilience of the first volunteers, and there were even reports of men retreating without orders.

IRA internal communication was an ongoing problem, which was made worse by rivalries between different units, and between rural members and the Headquarters in Dublin. The IRA newspaper spoke to the growing tensions:

“In other parts of the country […] things are still very unsatisfactory. It effects no credit on the Volunteers in these districts that they should leave the gallant men of the South to bear all the brunt of the enemy’s activities and thus help to make the military problems much simpler for the enemy. If the Volunteers throughout Ireland were as active as in parts of Munster […] the enemy would require a very much larger force […] and this would cause him very serious embarrassment. It would also relieve the strain on the gallant men in the “gap of danger”.” (Anonymous, An tÓglach)

The IRA was also running out of weapons. They tried to illegally import weapons, including Thompson submachine guns from the US, but gun-running was generally unsuccessful. To make matters worse, there was now more shooting to be done, since the British convoys were large and aggressive. After an ambush against police, in which the police fought back fiercely and chased off the IRA attackers, Headquarters concluded the raid still achieved its goals but this type of operation was quote “skating on very thin ice indeed.” (Townshend 242)

To solve the IRA’s problems, the Irish parliament pushed for reforms. It officially took responsibility for the IRA in early 1921, and sent organizers to the countryside to improve to discipline and training along more traditional military lines. The IRA also changed its tactics, and created Active Service Units in March. These smaller units replaced the flying columns, and some inactive brigades were simply disbanded. The reforms did provoke some resistance from experienced brigade leaders like Tom Barry and Sean Moylan – they viewed the changes as an attempt to impose overly-bureaucratic central control.

So both the British and the IRA were facing serious challenges to achieving their aims in the war – but there was no letup in the fighting. In fact, the first half of 1921 would be the bloodiest in the entire conflict, with both sides experiencing defeats as well as victories.

The spike in bloodshed began in February with a series of IRA ambushes that did not go well for the republicans. Then British forces surprised twenty men of the IRA 1st Cork Brigade a supposed safe house in Clonmult, and in the ensuing firefight 12 were killed and 8 arrested - the biggest loss of life for the IRA in a single action. In March, Tom Barry’s famous 3rd Cork Brigade was nearly captured after an IRA prisoner gave information to the British.

In fact, the British were capturing more and more IRA men as 1921 went on. By July, 4,500 IRA volunteers were in custody, including almost half of the 40 brigade commanders of the roughly 40 active IRA brigades. Only about 2000 IRA fighters remained active in the field. Holding so many prisoners meant the British had much better intelligence, which led to the near-capture of IRA intelligence chief Michael Collins in a raid on his office. He recalled his lucky escape in a letter:

“They just walked into the office where they expected to find me working. The information was good and I ought to have been there at the time. It happened, however, that I was not. Neither was my staff. It was the most providential escape yet. It will probably have the effect of making them think I am even more mysterious than they believe me to be, and that is saying a good deal.” (Hopkinson p. 228)

Perhaps even more damaging than the capture of men, was the capture of their equipment. By June and July, the IRA were suffering from severe shortages of weapons, especially rifles. And since police barracks were better defended than before, stealing rifles from them was a risky proposition.

So the IRA was attacking the British more often, but suffering heavy losses in return. But despite some failures, the overall increase in attacks put more pressure on the British, and the IRA benefitted politically from even limited success on the ground. And in March, they ambushed their most ambitious target yet.

IRA intelligence learned of a planned visit to County Kerry by Lt General Strickland, commander of the British 6th Division and regional military governor. On March 5th, 70 IRA men from Cork and Kerry brigades prepared to ambush him, under the command of Sean Moylan and Paddy O’Brien. The group was well-armed, with a Hotchkiss machine gun and land mines. They laid 6 mines along the road where Strickland was expected to pass. Around 2pm, a British convoy arrived, consisting of three trucks, an armoured car, and a touring car of the type used by British officers. Moylan’s official post-action report described the attack:

“We attacked but our mines failed to explode owing, probably, to the knocking about on the journey from Kerry. Our men opened fire on the leading lorry, and stopped it by killing the driver. The second lorry pulled up, and the touring car and armoured car almost dashed into it… The rear lorry came on until stopped by our rifle fire. There must have been a big roll of casualties in this car, as a very effective fire was poured into it from the north and west. After a 2 hour fight, in which the enemy machine guns searched the whole countryside, and which finally developed into a series of skirmishes over a large area, we retreated in good order after inflicting heavy casualties and without suffering any on our side.” (Townshend 243)

The British officer had been killed in the ambush, but it turned out that it wasn’t Strickland. Instead, the IRA had killed Brigadier-General Hanway Robert Cumming, commander of British troops in Kerry. A high-profile target had been hit, but the IRA operation was not flawless. Their intelligence about Strickland had been wrong, and only 4 British had been killed – in contrast to Moylan’s optimistic report.

But the killing of a British Brigadier General had a major impact. The 6th Division described the attack as “one of the worst reverses suffered by the army”, and Cumming is likely the highest ranking casualty of the entire war.

So as spring 1921 continued, the British and IRA continued clash in the countryside of the Martial Law Area. Now, the IRA’s political leadership, Sinn Fein, wanted to extend the war to Dublin.

Although victories in the rural areas were still essential for keeping strategic momentum, Irish Parliament President Eamon de Valera felt lasting political change could only come from influence in Dublin. IRA Chief of Staff Richard Mulcahy also recognised this dynamic:

“The grip of our forces in Dublin must be maintained and strengthened at all costs… it cannot be too clearly stated that no number nor any magnitude of victories in any distant provincial areas have any value if Dublin is lost in a military sense.” (Hopkinson p. 289)

Events in Dublin generated more attention abroad, but also in Britain – which meant the city was much more heavily garrisoned than provincial towns or villages. More British troops meant more opportunities for IRA attacks, but also presented problems. In the city, police units under attack cold quickly call on reinforcements, the narrow streets and alleys made it harder to trap British forces for ambush, and civilian casualties were more likely.

Because of these challenges, IRA operations in Dublin before 1921 were mostly intelligence-gathering or targeted assassinations of individuals. But by March 1921, de Valera was ordering the new Dublin Active Service Unit to attack the police at least three times a day, usually with quick handgun or grenade strikes. The Dublin ASU made 53 attacks in March, 67 in April, and 107 in May.

But these were small-scale affairs, and De Valera wanted a large symbolic operation that would further shake the foundations of British control in Dublin. Collins opposed the idea, but was overruled. The target chosen was the Dublin Custom House, an important British government building.

On May 25th, 120 men from the 2nd Battalion of the Dublin Brigade broke into the Custom House and set it on fire. All went as planned for the IRA until an Auxiliary patrol in an armoured car arrived on the scene. In the firefight that followed, 6 IRA men were killed, and over 80 surrendered - virtually wiping out the attackers. Sinn Fein publicly celebrated the raid as a victory, even though there were internal tensions about the heavy losses they’d taken.

By May 1921, both sides were becoming exhausted even as the intensity of the war continued to grow. Politically, the Republican cause was strong, but militarily the IRA was near breaking point. The British had the opposite problem: there were more troops in Ireland than ever before, but morale was low and Ireland remained a political disaster.

British plans for an election in Ireland failed, and Macready’s troops had failed to deliver a knockout blow. Prime Minister Lloyd George now acknowledge that de Valera was quote “the leader of the great majority in Southern Ireland” and offered to negotiate. His message to de Valera was clear: this was the only chance for a political solution. Refusal would bring all-out war.

The British offered the Irish Dominion status, which would have made Ireland a self-governing part of the empire like Canada or Australia. De Valera rejected this option, and suggested an informal ceasefire to allow for an agreement to be reached for an eventual treaty. Lloyd George agreed, but the details of the truce on the ground would be up to military commanders on both sides.

On May 8th, the two sides came to terms, although no formal written truce was signed. Instead, an oral agreement was made, which would cause some complications later on. Macready understood that he agreed to the following for the British side:

● No more raids and searches
● The military would be limited to supporting the normal duties of the police
● The lifting of curfews
● A suspension of reinforcements and supplies from England
● The replacement of the Royal Irish Constabulary in Dublin by the local police

The IRA promised to end attacks on Crown forces and government property, as well as provocative displays likely to cause disturbances to the peace.

And with that, just over two years of fighting came to a tense end. During that time, around 260 British soldiers, 360 police, 550 IRA fighters, and 200 civilians had died. Neither side could claim victory, but merely surviving was enough for the IRA, as historian J Bowyer Bell explains:

“The IRA tactics had not beaten the British, nor won the war, they had only prevented defeat - yet this in itself was triumph.” (Bowyer 42)

The truce, however, did not end conflict in Ireland. Sectarian violence continued in the north, often against Catholic enclaves in protestant areas, while provocations continued to threaten a renewal of violence. To Strickland, these all came from one side:

“The flaunting of Sinn Fein flags everywhere is trying the temper of the police rather highly… they are no doubt trying to make them break out - and it would work… It will be beyond human endurance for some people to lie down and be kicked by murderers. It appears that everything must be done on our side to avoid provocation, and nothing on theirs - and yet we are, or were, in the winning position.” (Townshend 310)

Strickland was not alone in thinking his side was winning. Many IRA leaders, including Collins, felt the truce was too premature and would give the British time to regroup. In reality, it was likely the republican movement which benefited most from the end of hostilities. Many of its institutions were buckling under pressure, and now they had the time they needed to regroup and rebuild.

However, what became clear was a growing fault line through the IRA and Sinn Fein. With the old enemy seemingly on the way out, tensions grew between comrades with different views of Ireland’s future. Although the Irish War of Independence was drawing to a close, another war would soon begin.



  • Anonymous. “The Enemy’s Failure”, An tÓglach, Vol. 2, No. 24 (March 1, 1921)
  • Bell, J Bowyer. “The Secret Army: The IRA” (London: Sphere, 1972)
  • Dorney, John. “War of Independence: the bloodiest six months”, The Irish Times, (3 June 2020)
  • Fairbrother, Henry. “The British Army Presence in Dublin” Dublin Historical Record,
  • Vol. 70, No. 1 (Spring / Summer 2017)
  • Hopkinson, Michael. “The Irish War of Independence”, (Cork : Gill & Macmillan, 2014)
  • Lawlor, S. M. “Ireland from Truce to Treaty: War or Peace? July to October 1921” Irish Historical Studies, Vol. 22, No. 85 (Mar., 1980)
  • O’Donoghue, Florence. “No Other Law” (Dublin : Anvil Books, 1986)
  • Townshend, Charles. “The Republic: The Fight for Irish Independence 1918-1923”, (London : Penguin Books, 2014)

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