'The War of the Irish with the Foreigners'

Written in Middle Irish, the Cogadh was composed sometime between 1103-1111 AD, nearly 100 years after the Battle of Clontarf. Focused on the battles of Sulcoit, Glen Mama, and Clontarf, the Cogadh is primarily concerned with the wars of Brian Boru and his lineage, the Dál Cais. The Cogadh begins in the nascent stages of Brian's political career and culminates with his martial endeavors at Clontarf in 1014.

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

These had for the purposes of Their battle and combat, and for their defence, sharp, swift, weapons. bloody, crimsoned, bounding, barbed, keen, bitter, wounding, terrible, piercing, fatal, murderous, poisoned arrows, which had been anointed and browned in the blood of dragons and toads, and water-snakes of hell, and of scorpions and otters, and wonderful venomous snakes of all kinds, to be cast and shot at active and warlike, and valiant chieftains.

They had with them hideous, barbarous, quivers; and polished, yellow-shining bows; and strong, broad green, sharp, rough, dark spears, in the stout, bold hard hands of freebooters. They had also with them polished pliable, triple-plated heavy, stout, corslets of double refined iron, and of cool uncorroding brass, for the protection of their bodies, and skin, and skulls, from sharp terrible arms, and from all sorts of fearful weapons."

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

The Cogadh as Propaganda

While the author of the Cogadh is still unknown, scholars have established that the text was created at the behest of Brian Boru’s great-grandson, Muirchertach. Muirchertach himself was an exceptionally powerful king, commonly considered the most effective descendant of Brian Boru. He was intent upon fulfilling his great-grandfather’s dream of bringing all of Ireland under his control, and was largely successful. Due to Muirchertach’s expansionist activities and influential reign, he probably commissioned the Cogadh as a piece of pro-Dál Cais propaganda.

Did you know? The Dál Cais, the ancestral line of Brian Boru, which would become the Uí Briain (literally Brian's descendants) did not have an illustrious genealogical background. Ireland had several dynasties with long-standing and well-respected genealogies, and the Dál Cais fabricated ties to one such ancestral line, the Eoganacht. These genealogical ties were so critical to the medieval Irish that without claims to ancestral prestige, the Dál Cais would never have been respected as rightful kings.

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The Cogadh is a work of propaganda composed to aid Muirchertach's political ambitions. Within this context, the precise intent of the author is debated. One possiblity is that the Cogadh was intended to highlight Brian's victory over the Munster rulers in order to send a powerful message to their descendants to illustrate they were indebted to the Uí Briain.

Another possibility is that the Cogadh was composed as a response to the King of Norway, Magnus Barelegs, and his expansionist forays into Orkney, the Hebrides, and the Isle of Man. 

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This placed Magnus in direct confrontation with the Uí Briain and Muirchertach, whose control extended to the Isle of Man and the Hebrides. Magnus' desire for power posed a growing threat, and a work designed to illustrate the magnitude of Muirchertach's dynastic power was a predictable response.


Anthony Candon, 'Muirchertach Ua Briain: Politics and Naval Activity in the Irish Sea' in Gearóid Mac Niocaill and Patrick F. Wallace (eds), Keimelia: Studies in Medieval Archaeology and History in Memory of Tom Delaney (Galway, 1988), pp 397-415.

Sean Duffy, 'The Western World’s Tower of Honour and Dignity: The Career of Muirchertach Ua Briain in Context' in Damien Bracken & Dagmar Ó Riain-Raedel (eds), Ireland and Europe in the Twelfth Century Reform and Renewal (Dublin, 2006), pp 56-73.

Fergus Kelly, A Guide to Early Irish Law (Dublin, 1988).

D.P. McCarthy, Irish Annals: Their Genesis, Evolution, and History (Dublin, 2008).

Máire Ní Mhaonaigh, 'Bréifne Bias in Cogad Gáedel re Gallaib' in Ériu Vol. 43 (Jan 01, 1992), pp 135-58.

Máire Ní Mhaonaigh, Brian Boru: Ireland’s Greatest King?  (Stroud, 2007).

Máire Ní Mhaonaigh, '"Cogad Gáedel Re Gallaib" and the Annals: A Comparison' in Ériu Vol. 47 (Jan 01, 1996), pp 101-26.

Máire Ní Mhaonaigh, 'The date of Cogad Gaedel re Galliab' Peritia 9 (1995), pp 354-77.

James Henthorn Todd, ed, intro. and trans. Cogadh Gaedhel re Gallaibh = The war of the Gaedhil with the Gaill, or, The invasions of Ireland by the Danes and other Norsemen (London, 1867).