In the annals of nineteenth-century Ireland, few disputes between public figures have been more rancorous or more significant than the fight that began in 1848 between two seemingly like-minded journalists, Charles Gavan Duffy and John Mitchel. In the mid-1840s, Duffy and Mitchel were colleagues on the most influential nationalist newspaper in Irish history, the Nation. But in 1847, relations between the two men became strained, and Mitchel resigned to start his own, more radical, paper. The former friends and colleagues soon became the bitterest of enemies. Their public quarrels over the next few years severely damaged each man's personal reputation — and also damaged the Irish nationalist cause in which each so fervently believed.

Unlike many running Irish feuds, which merely exacerbate old stereotypes about the Gaels being a fractious race, the Mitchel-Duffy controversy haddirect political fallout at a critical point in the development of political separatism in Ireland. The quarrel erupted just when Irish nationalists had an unusual opportunity to bring enormous pressure to bear on the British House of Commons. The Tory party of the 1840s had been shattered, first by Sir Robert Peel's turnabout on free trade in 1846, and then by Peel's death four years later. The modern idea of nearly automatic, lifelong adhesion to strong central parties was still some years off, and the two major British parties were scrambling for friends.