This book assesses the security threat and political challenges offered by dissident Irish republicanism to the Northern Irish peace process. Dissident republicanism ranges from those who consider armed struggle to be an essential element of any republican campaign to political reformers and campaign groups. The book charts the divisions in republicanism following the evolution of Sinn Féin into constitutional politics, leaving a rump of ‘militants’. Using in-depth interviews and access to a range of organisations it has been possible to explore the origins, strategy and goals of the various strands of republicanism evident in Northern Ireland today. This book considers the impact of various dissident groupings and their tactics within a post-Good Friday Agreement context and places armed republicanism in Northern Ireland within the broader debate on counter-terrorism after 9/11.