The thesis deals with East Tyrone's importance as a crucible of republican politics, a cockpit of sectarian tension and the battleground between Redmondite Hibernianism and the emergent forces of republicanism. It examines the development of republican politics in the early C20, from a northern perspective, concentrating on how popular ideology is formed and how the two nationalist ideologies (constitutional and separatist) and their leaderships attempted to harness the rhetoric of popular nationalism to generate support for their respective movements. It is the first attempt to examine the rise of northern republican and Hibernian politics (at times complementary but more often contradictory forces). As such, East Tyrone is employed as a case study for an exam!nation of the career of Joseph Devlin, arguably northern nationalism's most influential political figure. A wide source base is employed, including R.I.C. reports, private papers, witness statements and the local press, to examine the rhetorical tools employed to achieve popular support and how this support legitimised national agendas often contradictory to grass roots' expectations and the message delivered to the popular constituency. The local case study is employed to gain a greater understanding of how events at the level of high politics affect ordinary people, at times altering political consciousness. The thesis, therefore, synthesises a detailed local study with the wider historiographical debate on a crucial period in local, national arid international history. The thesis is theoretically informed by the hegemonic theory of Antonio Gramsci, particularly in relation to the development of political consensus and ideology's crucial role in this process. The important question of the generation and development of popular ideology relies on the theory of George Rude as outlined in his work Ideology and Popular Rhetoric, (London, 1980).