This thesis aims to shed light on the Basque National Liberation Movement strategy and why its armed front –ETA- decided to announce the definitive cessation of its armed activity on the 20th October 2011.Based on qualitative and quantitative analysis of interviews and document data I conclude that ETA responded rationally to a contradiction of its room for manoeuvre. Three main factors made it difficult for the Basque radical nationalist to uphold their ideological paradigm.(1) Loss of legitimacy in the Basque population.(2) Increased coordination by Spanish and French authorities.(3) Effective counter-insurgency methods by the Spanish security forcesKeywords: ETA, MNLV, Basque terrorism, room for manoeuvre.