Sources for the Battle

The most reliable sources for the Battle of Clontarf are the contemporary Irish annals (U1014.2, Annals of Ulster, AI1014.2, Annals of Inisfallen, M1013.11, Annals of the Four Masters), but they do not provide much detail other than a long list of men who fought and died at the battle.

The Cogadh Gaedhel re Gallaibh and Njál's Saga also provide important information on the battle, but they are later literary works and highly embellished so their reliability is limited.

The Siege of Dublin in 1013

Brian Boru became high-king of Ireland in 1002 with many groups submitting to his overlordship by giving him hostages.

However, his overlordship was not uncontested, and in 1013 he faced a rebellion led by Máel Mórda, king of Leinster, and Sitric Silkenbeard, king of Dublin (Máel Mórda's nephew).

Brian's son Murchad was sent to plunder in Leinster in retaliation, but Brian knew he had to deal with this rebellion personally:

Murchad son of Brian made a great raid into Laigin, plundered the land to Glenn dá Locha and Cell Maignenn, burned the whole country, and took great spoils and countless captives.

The Laigin and the foreigners began warring against Brian, and the Munstermen and Brian were encamped at Sliabh Mairce, and they harried Laigin as far as Áth Cliath."

U 1013.7 & 1013.12, Annals of Ulster in CELT.

In the autumn of 1013, Brian and his army moved towards Dublin and set up a camp south of the River Liffey.  His troops sacked and burned Clondalkin and Kilmainham and they laid siege to Dublin.  Brian's son Donnchad was sent out to look for supplies and plunder in Munster.

The siege, which took place some time around Christmas, was unsuccessful, and, according to the Cogadh, Brian retired shortly thereafter to his home in Munster.

The following spring (sometime around St Patrick's Day), Brian made another attempt to regain the submission of Dublin and Leinster.

The 1014 Campaign and the Two Armies

Brian's army was drawn largely from his native Munster and doubtless included some forces from the Viking towns of the province.  But he had other supporters as well including, it seems, the man he had replaced as high-king, Máel Sechnaill, the Uí Néill king.

Brian started his 1014 campaign north of the Liffey.  His troops plundered and burned Fine Gall (Fine Gall was the name given to a stretch of territory north of the river Liffey used by the Scandinavians of Dublin) and moved on the Howth.  While Brian's troops were burning and plundering Howth, an army left Dublin to engage them in battle.

The Dublin army consisted of Hiberno-Norse and Leinstermen and was under the command of Dubgall mac Amlaíb, brother of Sitric Silkenbeard, the Hiberno-Norse king of Dublin.  Further support came from Sitric's uncle Máel Mórda, king of Leinster. Both Sitric and Máel Mórda had previously submitted to Brian Boru and acknowledged him as their overlord, but now sensed an opportunity to reassert their independence. These kings supplemented their own strength with Viking forces recruited from the Isle of Man and the Orkneys (some of whom were of Danish origin) who were promised power and position in Ireland should they win. Sitric himself did not fight on the battlefield, but stayed in Dublin to ensure the town was protected against the enemy.

The Cogadh provides a biased description of the two armies.  The Vikings of Dublin are portrayed as hateful barbarians and pagans:

Now on the one side of the battle were the shouting, hateful, powerful, wrestling, valiant, active, fierce-moving, dangerous, nimble, violent, furious, unscrupulous, untamable, inexorable, unsteady, cruel, barbarous, frightful, sharp, ready, huge, prepared, cunning, warlike, poisonous, murderous, hostile Danars; bold, hard-hearted Danmarkians, surly, piratical foreigners, blue-green, pagan; without reverence, without veneration, without honour, without mercy, for God or for man."

James H. Todd, Cogadh Gaedhel re Gallaibh, p. 159.

In contrast, Brian's forces are described as strong, graceful knights:

But on the other side of that battle were brave, valiant champions; soldierly, active, nimble, bold, full of courage, quick, doing great deeds, pompous, beautiful, aggressive, hot, strong, swelling, bright, fresh, never-weary, terrible, valiant, victorious heroes and chieftains, and champions, and brave soldiers, the men of high deeds, and honour, and renown of Erinn..."

James H. Todd, Cogadh Gaedhel re Gallaibh, p. 161.

The Battle

According to some medieval sources, the Battle of Contarf was fought on Good Friday, 23 April 1014 near the coast north of the Hiberno-Norse city of Dublin.  Some scholars think the association with Good Friday was a later addition to the manuscripts in order to liken the death of the Christian king Brian and his victory over the heathens to Christ's death and the salvation of mankind.

Did you know?  Clontarf is actually not mentioned in the early accounts of the battle.  The first mention of Clontarf is in the twelfth-century Book of Leinster.  There is a list of kings of Leinster where it is stated that Brian Boru was killed in 'the Battle of Clontarf Weir (Cath Corad Cluana Tarb)'.

Brian's troops approached from the north, while the Dublin army came from the south and met their allies, a Viking fleet under the command of Bróđir, at the Clontarf Weir.

Professor Seán Duffy includes a plan of the battle in his recent book Brian Boru and the Battle of Clontarf (see below) and another plan in his recent article in History Ireland.  The interactive plan of the battle in our maps section is based on these two reconstructions (click on the maps displayed below to enlarge):

Seán Duffy, Brian Boru and the Battle of Clontarf (Dublin, 2013), p. 203.

Seán Duffy, 'What happened at the Battle of Clontarf?' in History Ireland, vol. 22, no. 2 (2014), pp 30-1: 31.

with special thanks to Tomás Ó Brógáin

The Cogadh tells us that the battle was of unprecedented scale and ferocity.  It involved numerous kings and was a bloody affair, lasting the whole day and claiming many lives.

The weapons of Brian's army are described as being particularly lethal:

steel, strong, piercing, graceful, ornamental, smooth, sharp-pointed, bright-sided, keen, clean, azure, glittering, flashing, brilliant, handsome, straight, well-tempered, quick, sharp swords, in the beautiful white hands of chiefs and royal knights, for hewing and for hacking, for maiming and mutilating skins, and bodies, and skulls."

James H. Todd, Cogadh Gaedhel re Gallaibh, p. 163.

Viking grave goods, Kilmainham, Dublin (James Plunkett, Watercolour 1847)

By evening, Brian's enemy retreated. Part of Sitric's and Bróđir's army headed for the safety of the fortress at Dublin, others however, attempted to reach their ships or escape via the woods towards Howth.

Brian's troops followed and they massacred the retreating enemy in a second battle near Dubgall's Bridge.  The Vikings that tried to flee to their ships faced a similar fate.  The returning tide had dispersed the Viking fleet across the Dublin Bay and the Viking warriors were trapped on Clontarf Weir between Brian's forces and the sea.  There was no escape, and many were drowned.

Brian at the Battle

By 1014 Brian Boru was an old man, probably in his late seventies, and he does not appear to have participated personally in the battle. Instead of fighting, it seems he left the command of his battlefield forces to his sons and deputies. In some sources he is portrayed praying in his tent nearby while awaiting news of the battle.

Painting of the Battle of Clontarf by Hugh Frazer in 1826

According to the Cogadh, Bróđir, the Viking leader, together with other Viking warriors fled the battlefield and came across Brian's camp.  The Cogadh records the dramatic moment that a praying Brian learns of their approach:

'There are people coming towards us here,' said the attendant.
'Woe is me, what manner of people are they?' said Brian.
'A blue stark naked people,' said the attendant.
'Alas!', said Brian, 'they to thee they come.'
While he was saying this, he arose and stepped off the cushion, and unsheathed his sword."

James H. Todd, Cogadh Gaedhel re Gallaibh, p. 203.

Bróđir thought first the high-king was just a priest, but when he realised it was Brian himself a fierce fight broke out and Bróđir killed the king.  Bróđir then fled the camp, but was hunted down by Brian's men and captured.  His fate was ritual disembowelment:

Then they threw a ring round Brodir and his men, and threw branches of trees upon them, and so Brodir was taken alive. Wolf the quarrelsome cut open his belly, and led him round and round the trunk of a tree, and so wound all his entrails out of him, and he did not die before they were all drown out of him."

George Webbe Dasent, Njál's Saga, p. 327.


The Irish annals record some of the important people who died during that day.

On the side of Brian's enemies, notable casualties of the battle included Dubgall mac Amlaíb (Sitric's brother), Máel Mórda (king of Leinster), and Sigurðr (the Earl of Orkney) who had been recruited for the battle.  Some sources claim Sitric watched the battle unfold from the ramparts of Dublin.  He certainly survived, and his death is recorded under the year 1042.

Brian Boru's army won the battle but it was at considerable cost.  Most significantly, he himself was killed.  In a further blow for his dynasty's future prospects as rulers of Ireland, Brian Boru's son Murchad and grandson Tairdelbach were also killed fighting in the battle.  The Cogadh describes both men as great heroes and describes their deaths as heroic.  Murchard is described as the 'royal champion' and he is compared to the Hebrew's Samson and the Greek hero Hercules.  Tairdelbach died fighting the Vikings who tried to flee into the sea.

It was then that Tordhelbhach, the son of Murchadh, son of Brian, went after the foreigners into the sea, when the rushing tide wave struck him a blow against the weir of Cluain-Tarbh, and so was he drowned, with a foreigner under him, and a foreigner in his right hand, and a foreigner in his left, and a stake of the weir through him."

James H. Todd, Cogadh Gaedhel re Gallaibh, p. 193.

Phillip Perry Creative Commons, Attribution-ShareAlike 2.0 license.

The immense scale of the battle, the persons involved, what had been at stake and the notable casualties meant it quickly gained legendary status.  The position of unprecedented power that Brian Boru had achieved during his career is reflected in the Annals of Ulster which, when recording his death, describes him as:

high-king of the Irish of Ireland and of the Foreigners and of the Britons, the Augustus of the whole of Northwest Europe."

In his Chronicon, a text which was supposed to record the history of the world up to 1082 AD, Marianus Scottus, an Irish monk who died at Mainz in 1082 or 1083, included the death of Brian Boru as an important event in both Irish and world history:

Brian rex Hiberniae parasceue paschae feria 6. 9 Kal. Mai manibus et mente ad Deum intentus occiditur; cui successit Donchad filius suus annis 51, nec quartam partem Hiberniae regnavit."

These and a series of later texts which elaborate and embellish the story of the Battle of Clontarf ensured that it became, arguably, the most famous battle in Irish history.

The Importance of the Battle

Brian’s victory at the battle of Clontarf fundamentally altered the ground-rules of Irish political history.  A little-known dynasty, the Dál Cais, had permanently broken Uí Neill dominance of the high-kingship of Ireland and defeated all challengers.

The battle has traditionally been viewed as primarily a local struggle: a political quarrel which pitted Munster against Leinster.  However, it is much more than that.  Professor Seán Duffy has recently stressed the importance of examining the traditionally underestimated wider insular context.

In 1013 England was enduring major Danish raids which eventually forced the Anglo-Saxon king Athelred unread (Aelthelred the unready or the ill-advised) into exile and heralded a new era with King Sweyn Forkbeard of Denmark claiming hegemony over both Denmark and England.

But by 1014 Sweyn was dead, his son, King Canute, had fled from England and Athelred had returned; the Danish project in Britain appeared to be stalling.  Although this Anglo-Saxon resurgence would not last, and Canute would indeed hold both kingdoms, this was unknowable in 1014. 

Were some of the Danish forces who we know were involved in the battle of Clontarf influenced by events in England?  Did the threat to Danish hegemony in Britain in 1014 inspire some of the participants to seek new opportunities in Ireland?  Might this Danish context explain why the outcome of this battle was heralded as a victory for Brian in spite of his death?  Brian had not only secured the high kingship and his own legacy, he had defeated the Danish threat and repelled the Viking invasion of Ireland.  Professor Duffy characterises the battle both as a fight for a new kind of high-kingship of Ireland and a spirited defence against those Danes who were seeking new lands and dominance in Ireland. 

Brian lost his life at the battle of Clontarf, and Ireland lost their greatest and mould-breaking high-king.  His victory at this final battle fundamentally altered contemporary politics and the future of Irish history. 

Is it any wonder his name looms large among the list of Irish heroes who gave their life for Ireland?



‘Brian Boru’, Bart Jaski, Medieval Ireland An Encyclopaedia, Seán Duffy (ed.), (NY, 2005).

Cathy Swift, ‘Brian Boru’s origins and the kingdom of North Munster’ History Ireland Special Issue: Brian Boru (March/April 2014), pp 18-20.

To download see:

Darren McGettigan, The Battle of Clontarf Good Friday 1014 (Dublin, 2013).

Donnchadh Ó Corráin, 'Brian Boru and the battle of Clontarf,' in Liam de Paor (ed.), Milestones in Irish History (Cork: 1986).

Downham, Clare, 'The Battle of Clontarf in Irish history and legend', History Ireland, 13, no. 5 (2005), p. 19-23.

Donnchadh Ó Corráin, ‘Dál Cais – church and dynasty’, Ériu, xxiv (1973), 52–63.Ní Mhaonaigh, Máire, Brian Boru: Ireland's Greatest King? (Stroud, 2008).

History Ireland Special Issue: Brian Boru (March / April 2014).

Ní Mhaonaigh, Máire, 'A neglected account of the Battle of Clontarf,' Zeischrift fur Celtische Philologie, 59 (2012), p. 143-167.

Máire Ní Mhaonaigh, 'Brian Bórama (Bóruma, Boru)', in James McGuire and James Quinn (ed.),
Dictionary of Irish Biography (Cambridge, 2009).

Seán Duffy, 'What happened at the Battle of Clontarf?', in History Ireland, vol. 22, no. 2 (2014): 30-33.

Seán Duffy, Brian Boru and the Battle of Clontarf (Dublin, 2013).

John Ryan, ‘Brian Boruma, king of Ireland’ in Etienne Rynne (ed.), North Munster studies: essays in commemoration of Monsignor Michael Moloney (1967), 355–74.


Primary Sources:

U1014.2, Annals of Ulster,

AI1014.2, Annals of Inisfallen,

M1013.11, Annals of the Four Masters

The Cogadh is discussed in the Remembering section of this website.