The Battle of Clontarf (Irish: Cath Chluain Tarbh) took place on 23rd of April in 1014 (23 April) between the forces of Brian Boru and the forces led by the King of Leinster, Máel Mórda mac Murchada: composed mainly of his own men, Viking mercenaries from Dublin and the Orkney Islands led by his cousin Sigtrygg, as well as the one rebellious king from the province of Ulster. It ended in a rout of the Máel Mórda's forces, along with the death of Brian, who was killed by a few Norsemen who were fleeing the battle and stumbled upon his tent. After the battle, Ireland returned to a fractious status quo between the many small, separate kingdoms that had existed for some time.
Brian Boru (Brian mac Cennétig) had ruled most of Ireland since 1002, but the island was still highly fractious and the title of "High King" had been largely ceremonial. Brian looked to change this, and unite the island, which he set about doing over a period of years.
In 997, Brian Boru and Máel Sechnaill mac Domnaill had met in Clonfert and reached an agreement where they recognized each other's reign over their respective halves of the country. Brian attacked Máel Sechnaill's territory constantly, which forced Máel Sechnaill to resign his land to Brian.
In 1012, the king of Leinster, Máel Mórda mac Murchada, rose in revolt. His attempts were quickly thwarted when Brian arranged a series of cross-marriages, giving his daughter to Sigtrygg Silkbeard, leader of the Dublin Vikings, and himself marrying Sigtrygg's mother and Máel Mórda's sister, Gormlaith. However this alliance was destined not to last, and in 1013 Máel Mórda again went to the Sigtrygg after being admonished by Gormlaith for accepting Brian's rule. This time Sigtrygg was ready to fight, and various Irish clans who were envious of Brian quickly joined.
Brian immediately imprisoned Gormlaith, and went on a series of raids around Dublin in order to tie down any Irish who would attempt to join the Viking forces. Meanwhile Gormlaith contacted Sigurd Lodvesson, the Viking earl of the Orkney Isles, to come to her aid. He not only agreed, but in turn contacted Brodir of the Isle of Man to join the fight. Sigurd and Brodir both planned on killing the other after the battle to take the seat of High King for themselves, while Sigtrygg was busy trying to form alliances with everyone involved in an attempt to at least retain his own seat in Dublin.
In 1014, Brian's army had mustered and set off towards Dublin. As they approached, the Irishmen of Meath, commanded by ex-high king Máel Sechnaill mac Domnaill, refused to take part in the battle. This left him with 4,500 men, outnumbering the 1,000 or so under Sigtrygg, but considerably worse equipped in comparison. They arrived outside the walls of Dublin and set up camp.
That night Brian received news that the Viking forces had boarded their longships and headed out to sea, deserting Sigtrygg. This was in fact a ruse. After nightfall they turned around and landed on the beaches of Clontarf, just over a mile to the north of Dublin, in order to surprise Brian's army the next day. At the time Dublin was only on the south shore of the River Liffey, connected to the north bank, and Clontarf, only by a single bridge. This allowed the Vikings time to disembark and prepare in relative safety.
The Viking army formed up into five divisions on the field, while Sigtrygg and 1,000 of his men remained in town. Sigtrygg's son commanded the extreme left of the line with 1,000 of the men from Dublin who decided to fight in the open. Máel Mórda added another 3,000 men from Leinster in two divisions. Although numerous, they too were poorly armed in comparison to the Vikings on either side. Sigurd's Orkney Vikings manned the center with 1,000 men, and Brodir's Vikings added another 1,000 or more on the right, on the beaches.
Brian's forces were arranged in a similar fashion. On the right (the Viking left) were 1,000 foreign mercenaries and Manx Vikings. Next to them, 1,500 clansmen of Connacht were gathered under their kings, while more than 2,000 Munster warriors under Brian's son Murchad continued the front, flanked by 1,400 Dal Caissans on the extreme left led by Murchad's 15-year-old son, Tordhelbach, and Brian's brother, Cuduiligh. Off to the right and several hundred yards to the rear stood Máel Sechnaill's 1,000 men who simply watched.
The battle opened with several personal taunts between men in either line, often ending with the two men marching out into the middle of the field to enter personal battle, while the forces on either side cheered. While this went on the two groups slowly edged towards each other. They engaged early in the morning.
At first the battle went the Vikings' way, with their heavier weapons prevailing over their opponents as everyone had expected. This advantage also served Brian, whose Viking mercenaries on his right slowly pushed back the forces facing them. On the left, Brodir himself led the charge and gained ground, until he met the warrior Wolf the Quarrelsome, brother of King Brian. Although Wolf was unable to break Brodir's armor, he knocked him to the ground and Brodir fled to hide. This left the now leaderless Viking force facing Murchad's forces, who considered themselves the "king's own" (containing many of Brian's more distant relatives) and by the afternoon Brodir's forces were fleeing to their ships.
In the center things were going more the Vikings' way. Both Sigurd's and Máel Mórda's forces were hammering into the Munster forces. However Sigurd, according to legend, carried a "magical" standard into battle which drew the Irish warriors to it, eventually forcing their way in and killing the bearer. Although the standard was supposed to guarantee a victory for the bearer's forces, it also guaranteed the bearer's death. No one would pick it up due to its reputation, so Sigurd did and was quickly killed.
By the end of the day, after several mutual pauses for rest, the Vikings found themselves with both flanks failing, Sigurd dead, and everyone exhausted. The beaches in front of the ships were already lost, and many men took to trying to swim to the ships further offshore, drowning in the process. The battle was now clearly going Brian's way, and the Dublin Vikings decided to flee to the town. At this point Máel Sechnaill decided to re-enter the battle, and cut them off from the bridge. The result was a rout, with every "invading" Viking leader being killed in the battle.
Meanwhile Brodir, hiding in the woods near Dublin, noticed Brian praying in his tent. Gathering several followers they ran into the tent and killed him and his retainers. Then they retreated, with Brodir yelling, Now let man tell man that Brodir felled Brian. According to Viking accounts, he was eventually tracked, captured and gruesomely killed by Wolf the Quarrelsome with whom he had clashed earlier on the battlefield.
Of the 6,500 to 7,000 Vikings and allied forces, an estimated 6,000, including almost all the leaders, were killed. Irish losses were at least 4,000, including their king and most of his sons. There was no longer any clear line of succession.
With the Irish now leaderless, and the power of the Dublin Vikings as a political force broken, Ireland soon returned to a series of bloody factional fighting. However things had changed as a result of the battle, with Viking and Gaelic culture no longer contesting power. After a number of years this led to a lasting peace, and the Vikings would instead turn to England and Scotland, eventually taking power when Canute the Great was installed as King in 1016.
Sigtrygg, who had watched the battle with Gormlaith from Dublin, on the south bank of the River Liffey, and with the Irish army melting away the next day, ended up as the only "winner" of the contest, continuing his rule in Dublin until his death in 1042. The Kingdom of Meath also benefitted from the fact that their warriors suffered few casualties, and managed to come from the battlefield in a much stronger position, with most of his neighbours, including the Dublin Vikings, all incapable of launching further advances. However the series of wars had resulted in a fragmented political landscape, which could not unite under the old High King.
A fictionalized (including fantasy elements) telling of the battle is the core of the short stories The Twilight of the Grey Gods and "The Cairn on the Headland" by Robert E. Howard.
The same author also wrote a straight-adventure story describing the battle, titled "Spears of Clontarf".
A fictionalized telling of the battle can be read in Lion of Ireland by Morgan Llewellyn.
The Battle of Clontarf is the subject of Cecelia Holland's novel "The Kings in Winter", pub. 1968.
In Star Trek: Deep Space Nine, the Irish character of Miles O'Brien was fond of recreating the battle in Deep Space 9's holosuites. In the episode "Bar Association", he and his friend Doctor Julian Bashir garbed themselves in traditional costume of the day. When Bashir asked why O'Brien had the right to portray Brian Boru, O'Brien explained that he was a direct descendant of the King.
A fictionalized retelling (based on the sagas) of these events can be found in Odinn's Child, the first book of Tim Severin's Viking series.
A fictionalized tale, "Sword Of Clontarf" written by Charles A. Brady, is very largely based on the Battle of Clontarf and the events preceding it. (Doubleday, 1960.)
The tale "The Mirror and the Mask" by the Argentinian writer Jorge Luis Borges (see The Book of Sand) is set around the time of the battle and mentions it in its opening. It is not clear whether the narrative takes place during or immediately after the battle; according to the story, the High King was not killed and asked his poet to elaborate an epic poem in the fashion of Virgil's Aeneid. The poet attempts to write an ever more improved work three times and each time is rewarded with an item; per the story's title, the first two are a silver mirror and a golden mask. By the third reworking, the poem has become but a single line, no longer about the specific battle but about "battle and the uttermost Beauty". The King's third gift is a dagger with which the poet then kills himself,
The novel Vinland by George Mackay Brown includes a long and detailed depiction of the battle, in which its protagonist takes part.
An account of this battle is the central motif of the album Cluain Tarbh, by Gaelic doom metal band Mael Mórdha. Their debut on Grau records Gaeltacht Mael Mordha details the events leading up to the battle through the eyes of the High King.
The Celtic/Black Metal band Mag Mell have a song named Wolf Felled Brodir which explains how Brodir slew Brian and how Wolf avenged his brother, thus "Wolf Felled Brodir" instead of Now let man tell man that Brodir felled Brian.
Celtic Folk Metal band Cruachan have numerous songs, including "Ard Rí na hÉireann" and "1014 AD".