To what extent does the relative strength of a rebel movement impact upon the likelihood of a peace settlement in civil conflict? This article argues that relatively stronger rebels are more likely to overcome the strategic bargaining problems that can prevent the resolution of war. Relatively strong insurgents are better equipped to significantly challenge core government interests and fundamentally threaten the survival of a regime. The incumbent’s fear of future violence therefore makes mediation more likely to be undertaken in high-stakes conflicts between states and strong rebel groups. Relatively strong insurgencies are also those with the greatest leverage to negotiate enforcement mechanisms and the best equipped to defend themselves in the event that the government reneges on an agreement. This reduces the scale of the commitment problem and increases the probability of relatively strong rebel groups agreeing to a settlement with an incumbent. This argument is tested using dyadic data that capture the relative position of insurgents in civil war from 1946 to 2004. This represents an important methodological shift within the mediation literature, which has in the past largely relied upon aggregate country-level data. The results suggest that relatively stronger insurgents are more likely to force the state to open a mediation process and eventually concede some form of settlement. This is further evidence of the need to capture the dyadic relations between actors with fine-grained disaggregated data.