The question of how armed group ideology influences its behaviour has been tentatively explored in the past decade. However, which role distinct ideological commitments play in civilian targeting has not been satisfactorily discussed thus far. This thesis turns to research on genocide and mass violence and incorporates the concepts of ‘exclusionary ideologies’ and ‘threat perceptions’ to fill this research gap. It addresses the following question: to what extent do exclusionary ideologies of armed groups influence their use of violence against civilians during civil conflicts? When revolutionary armed groups pursue their goals, threat perceptions determine which groups are considered legitimate targets for attack. Therefore, it is hypothesized that exclusionary groups will employ more violence against civilians than inclusionary groups because the former have a more expanded understanding of legitimate targeting than the latter. Through a structured focused comparison, discourse analysis and process tracing applied to the cases of Boko Haram and Al-Shabaab, moderate support for this hypothesis is found. It is shown that both armed groups to varying extents invoke threat perceptions regarding certain out-groups to legitimize and rationalise their patterns of violence. Nonetheless, a descent into indiscriminate violence by Boko Haram and data shortage of Al-Shabaab attacks warrant caution.