Barbara F. Walter's article "The Critical Barrier to Civil War Settlement" explores why civil wars rarely end in negotiated settlements, unlike interstate wars. Between 1940 and 1990, only 20% of civil wars reached such settlements, while 55% of interstate wars did. The author argues that the inability to arrange credible guarantees on the terms of the settlement is the primary reason for the failure of civil war negotiations. Civil war adversaries cannot demobilize, disarm, and disengage their military forces without a third party to enforce the peace agreement. Without such an enforcer, negotiations fail because the terms of the settlement are seen as too dangerous and vulnerable. The article proposes a theory of civil war resolution based on reciprocal problems of enforcement and vulnerability, rather than innate differences or goals. It tests this theory against 41 civil war cases and concludes that successful negotiated solutions can be implemented and maintained with outside intervention. The findings suggest that only when an outside power guarantees the terms of the peace treaty do commitments to disarm and share political power become credible, making cooperation possible.Barbara F. Walter's article "The Critical Barrier to Civil War Settlement" explores why civil wars rarely end in negotiated settlements, unlike interstate wars. Between 1940 and 1990, only 20% of civil wars reached such settlements, while 55% of interstate wars did. The author argues that the inability to arrange credible guarantees on the terms of the settlement is the primary reason for the failure of civil war negotiations. Civil war adversaries cannot demobilize, disarm, and disengage their military forces without a third party to enforce the peace agreement. Without such an enforcer, negotiations fail because the terms of the settlement are seen as too dangerous and vulnerable. The article proposes a theory of civil war resolution based on reciprocal problems of enforcement and vulnerability, rather than innate differences or goals. It tests this theory against 41 civil war cases and concludes that successful negotiated solutions can be implemented and maintained with outside intervention. The findings suggest that only when an outside power guarantees the terms of the peace treaty do commitments to disarm and share political power become credible, making cooperation possible.