Mitchel began writing for the Nationalist paper The Nation, and when Thomas Davis died in 1845, Charles Gavan Duffy invited Mitchel to join the newspaper. In 1846, Mitchel and other Young Irelanders broke with Daniel O'Connell, rejecting the doctrine of 'moral force', and founded ‘The Irish Confederation’.
More impatient than Duffy, Mitchel soon left The Nation and the Confederation, and in February 1848 published the first issue of The United Irishman. It openly preached revolt and in May 1848 Mitchel was convicted of ‘treason felony’ by the British and sentenced to fourteen years' transportation.
Sent to Van Diemen's Land (now Tasmania), Mitchel escaped in 1853 to America, where he published his famous Jail Journal.
Mitchel launched several newspapers in America, and as editor of the Richmond Examiner championed slavery. His sons fought in the War for the Confederacy. He was imprisoned for several months after the Civil War ended. In 1867, he founded the Irish Citizen in New York, but angered Fenians by suggesting they should give allegiance to their new country. In 1875, he was returned unopposed as MP for Tipperary, but was disqualified as a convicted felon. Returning to Ireland, he was again elected, but died at Dromalane, Newry, on 20 March 1875 before he could be unseated.
While today his stance on Slavery would be looked on with askance his posthumous claim to fame is undoubtedly his masterly ‘Jail Journal’ which is still in print today and in this he describes his imprisonment and Transportation to Van Diemen's Land in a British prison ship.
May 27, 1848 - On this day, about in the afternoon, I, John Mitchel, was kidnapped, and carried off from Dublin, in chains, as a convicted “Felon.”...
Nov. 7th, 1848 - In my cell, "Dromedary" Hulk. - This evening, after dusk, as I sat at my window, looking drearily on the darkening waters, something was thrown from the door of my cell, and lighted at my feet. I heard a quick noiseless step leaving the door. Picking up the object, I found it to be a London paper. The Halifax mail has arrived – I long for the hour when my cell is to be locked, and carefully hide my treasure till then.
At last the chief mate has locked and bolted me up for the night. I light a candle, and with shaking hands spread forth my paper.
Smith O’Brien has been found guilty, and sentenced to be drawn on a hurdle to the place of execution and hanged. The other trials pending.