William "Smith O'Brien" was a landed Protestant gentleman in County Clare whose family traced its ancestry to Brian Boru. He became an Irish nationalist Member of Parliament and a leader in Daniel O'Connell's movement to repeal the Act of Union with Great Britain. With O'Connell's imprisonment in 1844, the Repeal Association fell into disarray, and the more militantly radical Young Ireland movement gained authority, led by Smith O'Brien and others. It formed the Irish Confederation in 1847 and staged an abortive armed uprising in 1848.
In July 1848, a detachment of Young Irelanders led by Smith O'Brien attacked a unit of the Royal Irish Constabulary in Ballingary, a town in County Tipperary. They carried a new flag, the tricolor that now represents the Republic of Ireland, in imitation of French revolutionaries who carried their own tricolor through the streets of Paris earlier in the same year. Forty-seven policemen barricaded themselves in a large farmhouse, holding five children as hostages and ignoring pleas from the children's mother to free them. When gunshots interrupted O'Brien's attempt to negotiate the children's release, several people died.
O'Brien was apprehended, charged with high treason, convicted, and, with three others, sentenced to hanging, drawing, and quartering—one of the last impositions of that sentence in British history. After 80,000 people in Ireland and England signed petitions for clemency, and at the insistence of Queen Victoria, who decided that the punishment was a touch harsh for the crime, his sentence was commuted to penal servitude, and he was transported to Van Diemen's Land (Tasmania). In 1854 he received a conditional pardon and resettled in Brussels. In 1856 he received a full pardon and returned to Ireland, but he did not return to politics.
James Stephens was present in the Ballingary action and was wounded by gunfire, but escaped capture by feigning death. After fleeing to Paris, he returned in the 1850s to found the Irish Republican Brotherhood, the counterpart of the Fenian movement in America. This connection between the two men, and their respective revolutionary movements, makes it possible that it is this "O'Brien" that Bloom thinks of in Calypso, just after thinking of Stephens. But Gifford notes that there are two other plausible candidates: J. F. X. O'Brien, a Fenian arrested in 1867, and J. P. O'Brien, superintendent of the baths in Tara Street. In the context of the sequence of Bloom's thoughts, the last of these men is perhaps the most likely.
In Hades, the last sight from Bloom's carriage, before it passes over the Liffey and under "the hugecloaked liberator's form," is "Smith O'Brien. Someone has laid a bunch of flowers there. Woman. Must be his deathday. For many happy returns. The carriage wheeling by Farrell's statue united noiselessly their unresisting knees." Gifford says that O'Brien did indeed die on June 16, but most sources record his "deathday" as 18 June 1864.
The marble statue of O'Brien sculpted by Sir Thomas Farrell (who also made Sir John Gray's statue) was erected in 1869-70 at the intersection where D'Olier and Westmoreland Streets join, just south of O'Connell Bridge. This is where Bloom catches sight of the monument. But in 1929 Farrell's statue was moved north, across the river to a new location on O'Connell Street, beyond the statue of O'Connell.
In Circe, when "Pandemonium" breaks out and Irish heroes fight duels with one another, one of the matches is "Smith O'Brien against Daniel O'Connell." Although the spirit of the passage is absurdist, there is some historical basis for this opposition. Smith O'Brien always supported Catholic Emancipation, but he at first opposed O'Connell's movement to Repeal the Act of Union. When O'Connell was arrested in 1843 for conducting his "monster meetings," however, Smith O'Brien joined the Repeal Association and became its second most influential voice. After O'Connell's death he allied himself with those who pursued more militant, non-parliamentary avenues to independence—a more radical step than O'Connell was ever willing to take.
The two men thus did not always see eye to eye, and indeed the whole climate of Irish political organizing in the 1830s and 40s was marked by such violently shifting alliances and acrimonious recriminations that Circe's picture of "duels with cavalry sabres" is not a completely unapt analogy.