The Irish Republican Army and Sinn Fein, the political party allied to it, are both revered and reviled in Irish history: revered for their role in the Irish War of Independence, which ended in qualified independence for Ireland; reviled for their role in the Northern Ireland Troubles, which led to thousands of deaths between 1969 and 1998. However, between these two periods, the movement, which was committed to creating a unified Irish Republic, underwent several decades of ferment and transition. The struggle between the socialists and militarists was the central conflict at the heart of the Republican movement. I examine this conflict through a study of both historical and literary sources. The focus on literature by members of the IRA distinguishes this thesis from other studies of the period. I argue that the IRA was more successful when it adopted a socialist political strategy and by contrast, was most divided and unpopular when it adopted a purely military strategy. I divide the period into three sections. The first, from 1926 to 1934, addresses IRA socialism led by Peadar O’Donnell, focusing especially on O’Donnell’s campaign against land annuity payments and his novels. The second, from 1934 to 1962, deals with period of militarist ascendancy in the movement. I also use the works of two socialist IRA members to show the potential for socialism to reemerge. The third treats the period from 1962 to 1969, which saw the socialists take charge, and I analyze their pamphlets and newspapers. I end with a discussion of the split between the militarists and the socialists in 1969, demonstrating that these ideologies reached a moment of irreconcilability.