Policymakers and scholars alike have wrestled with the question of why some third-party interventions in fragile and conflict affected states (FCAS) are successful while others are not. For example, countries such as Cambodia, Rwanda, and Uzbekistan have been pulled out of extreme fragility, whereas countries such as Libya, Mali, and Zimbabwe remain mired in extreme fragility despite numerous attempts at spurring economic, social, and political development. This dissertation examines post-intervention variations in the development and security outcomes in otherwise similar fragile countries, in order to explain why some Western interventions have failed while others have succeeded. By documenting key cases of third-party intervention in FCAS and examining them systematically this research program tests structural aspects of each country situation while at the same time accounting for agency and leadership roles, both domestically and internationally. Using a theoretical framework based on the evolutionary biology principles of alternative stable states and positive feedback loops, the findings indicate that there is some evidence that—perhaps counter intuitively—outside interventions should focus initially not on the weakest state fragility dimension (authority, legitimacy, and capacity) but rather on the strongest. For states stuck in extreme fragility for long periods of time, the level of each of the three dimensions is so low that focusing on the weakest dimension only leads to premature load bearing and isomorphic mimicry problems (Andrews, Pritchett and Woolcock 2017). Rather, interventions which target the strongest dimension of fragility lead to improvement by establishing self-reinforcing, 'runaway' positive feedback loops. At the same time, the findings indicate that intervention on the strongest dimension may be a necessary but not sufficient factor in catalyzing recovery, and that certain preconditions or concurrent conditions may be needed to ensure that these 'virtuous cycles' have a positive feedback effect on the other two dimensions of fragility, improving development and security outcomes and catalyzing long-term recovery in state authority, legitimacy, and capacity.