Cogad Gáedel re Gallaib

The chronicle, which compares King Brian to Augustus and Alexander the Great, was written in the early twelfth century, at least a hundred years after the events it describes.

[3] The author makes extensive use of long, elaborate passages that describe and highlight the contrast between the Irish king Brian and the foreign army he wars against.

Brian and his followers are described in terms of their virtue and courage, often emphasising their Christian background and piety: 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...[4] The text goes on to say that Brian and his Dál gCais are comparable to Augustus and Alexander the Great, even going on to suggest that Brian's son Murchadh "was the metaphorical Hector of all-victorious Erinn, in religion, and in valour, and in championship, in generosity, and in munificence.

[6] In contrast with the lavish praise bestowed on the Dál gCais, the text describes the Vikings with vehemence and condemnation, though in terms no less hyperbolic: Now on the one side of that 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.

[7] The text's censure of the foreigners elevates the Irish and Brian even further, setting up a striking difference in moral and religious character between the two groups.

This was an issue because the Ua Briain sept of the Dál gCais was struggling to remain the High Kings of Ireland at the time of the chronicle's writing.

[11] The narrative of the Cogad begins with the arrival of the tyrannical Ivar of Limerick,[12] this only after a long introduction, the "first part" is composed primarily of annalistic material.