The Irish Republican Brotherhood (IRB) was one of the most important revolutionary organizations within Irish history and had a profound influence on the emergence of Ireland as we understand it today. It was a key factor in the emergence of cultural and political organizations in the late nineteenth and early twentieth centuries, played an active role in the Irish Revolution of 1916-21 and was a crucial group in terms of the negotiation of the Anglo-Irish Treaty of 1921 and the emergence of the Irish Free State. Here the story of the IRB and the Fenian conspiracy are told for the first time through photographs.