What explains the great variation in conflict intensity? In this article, I argue that insurgent ideology helps answer this question. Revolutionary ideology, characterised by ambitions of transforming society, causes deadlier conflicts for four reasons. Revolutionary ideology leads insurgents to 1) spread the conflict geographically wide, 2) perpetrate indiscriminate violence against perceived enemy groups, 3) carry out selective violence for moral infractions and 4) be more motivated to fight. Statistical analysis on insurgencies from 1989 to 2024 demonstrates that revolutionary insurgencies generate significantly more battle-related deaths and one-sided violence against civilians.
