The Fenian Brotherhood was a United States-based Irish republican revolutionary movement which was founded in 1858 by John O'Mahony and Michael Doheny as the North American branch of the Irish Republican Brotherhood. The Fenians were a secular revolutionary movement devoted to an armed struggle against Britain with the goal of creating an independent Irish republic, and it took its name from the Fianna warband of the legendary Celtic warrior Finn McCool. The Fenians experienced large-scale growth after the end of the American Civil War in 1865, with many Irish-American Union Army veterans joining the Fenian Brotherhood with the intention of using their newly-acquired military experience to continue the fight against British tyranny in the Americas. From 1866 to 1871, the Fenians launched raids into British Canada to pressure the British to withdraw from Ireland, but the Protestant Irish-Canadians sided with the British, leading to the failure of the Fenians' plans to provoke an Irish uprising in Canada.
Meanwhile, the Fenians also became involved with US politics. The editor of the Irish Republic noted the similarities between the plight of the African-Americans and that of the Irish immigrants, and the radical black New Orleans newspaper Tribune wrote in 1866 of the African-Americans' support for the independence of all nationalities and their support for a republican government in Ireland. Some Radical Republicans such as Charles Sumner, Benjamin Butler, and Zachariah Chandler attempted to win over Irish voters by expressing Fenian sympathies, and Fenian journalist Michael Scanlan echoed Republican ideas, accusing Democratic president Andrew Johnson of being poorly educated and supporting protective tariffs on the grounds that they would protect Irishmen's wages from British competition.
However, some Fenians such as John Mitchel affiliated themselves with the conservative Democrats, sympathizing with Southern whites due to their comparison of Northern "despotism" with British tranny, as well as criticizing the poor treatment of Irish Catholic immigrants by nativists within the Republican Party. These Fenians identified more with the poor and "oppressed" Southerners than with African-Americans, partially due to economic and political reasons, and partially due to racial animosity towards blacks. Southern newspapers such as Charleston's Daily Courier, Galveston's Weekly News, and Macon's Daily Telegraph compared the Reconstruction to the brutal British occupation of Ireland, and they also pointed out the hypocrisy of Irish Republican voters, asking how they could support the North as it "visit(ed) upon the South the same iniquities, a hundred-fold intensified, under which Ireland suffer(ed)." A Ku Klux Klan leader in North Carolina also compared his efforts to those of the Irish revolutionary martyr Robert Emmet in 1803.
In any event, the Irish were denied political enfranchisement for decades to come, with Cleveland's Republican Morning Leader declaring that Ireland was not yet ready for self-government, let alone emancipation from British rule. The Fenian Brotherhood voted to disband in 1880, and it was replaced by Clan na Gael.