This study is concerned with how ethno-nationalist/separatist terrorism is countered within liberal democracies and what impact government responses have on how a conflict involving the use of terrorism is transformed from one of violence to constitutional political activity. Specifically, we are concerned with the balance between coercive and conciliatory responses. A moderate terrorism studies approach is used, which focuses on root causes of terrorism and places them in a historical context ranging from the historical precedents of a terrorist campaign to when a group reaches a permanent and verifiable ceasefire. The study combines theories from within terrorism studies and conflict studies to develop a theoretical framework, in which the relational conflict triangle model of situation-attitudes-behaviour is informed by academic knowledge on terrorism. In order to put the study into context preliminary matters are addressed as to what ethno-nationalist/separatist terrorism is and the relationship between terrorism and liberal democracy. The following chapters introduce conflict studies, terrorism studies, and develop the theoretical framework, noting the convergence of interests between the two disciplines. The framework is then tested by comparing three protracted cases of ethnonationalist/separatist terrorism in the Basque Country, Corsica and Northern Ireland. The analysis centres on the terrorist groups involved and how they come to emerge and, in many cases, reach the decision to abandon violence. The analysis is historical and takes into account the situation, attitudes and behaviour of the protagonists involved, noting the proneness of terrorist organisations towards volatile division. The conclusion drawn is that a combination of coercion, conciliation and reform led to the eventual ending of terrorist campaigns in the three cases but conciliation and reform were dependent on the use of coercive measures targeted directly at the groups involved. The reasons for splinter groups continuing violence are also discussed.