The Irish Republican Brotherhood (IRB; Irish: Bráithreachas Phoblacht na hÉireann) was a secret oath-bound fraternal organisation dedicated to the establishment of an “independent democratic republic” in Ireland between 1858 and 1924

In 1798 the United Irishmen, which had initially been an open political organisation, but which was later suppressed by the British establishment in Ireland and so became a secret revolutionary organisation, rose in rebellion, seeking an end to British rule in Ireland and the establishment of an Irish Republic. The rebellion was suppressed, but the principles of the United Irishmen were to have a powerful influence on the course of Irish history.

Dublin Castle was the seat of government administration in Ireland and was appointed by the British cabint and was accountable only to the cabinet, not to the House of Commons and not to the Irish people or their political representatives. Irish MPs could speak at Westminster in protest about the actions of the administration, but its privileges were unchallengeable as Irish representation in the House of Commons was only one sixth of the total and far too small.

Fenianism therefore, according to O’Mahony is symbolised by two principles: Firstly, that Ireland had a natural right to independence, and secondly, that that right could be won only by an armed revolution .Because of their belief in republicanism, that is, the “common people are the rightful rulers of their own destiny,” the founding members saw themselves as “furious democrats in theory” and declared their movement to be “wholly and unequivocally democratic.” Being a democrat and egalitarian in the mid 19thcentury was tantamount to being a revolutionary, and was something to be feared by political establishments.

It was Stephens “firm resolution to establish a democratic republic in Ireland; that is, a republic for the weal of the toiler,” and that this would require a complete social revolution before the people could possibly become republicans. In propagating republican principles, they felt, the organisation would create this virtual democracy within the country, which would form the basis of an independence movement.

The Fenians soon established themselves in Australia, South America, Canada and, above all, in the United States, as well as in the large cities of England, such as London, Manchester, Liverpool, and Glasgow, in Scotland.