Introduction: This policy brief seeks to understand the sources of strength of armed non-state actors and to explain why stronger state actors have sustained difficulties in defeating them on the tactical, operational and strategic levels. The brief is divided into four sections. First, it demonstrates a historical change in battle/conflict outcomes involving armed state actors (represented by incumbent governments or regimes) and armed non-state actors (represented by rebels or insurgents). Second, it gives an overview of the main explanations in the Security and Strategic Studies scholarly literature explaining that historical change in outcomes. The third part reviews the strategy(ies) of selected state actors in dealing with the military rise of armed non-state actors. The final section of the brief provides concluding observations.