Civil war usually has devastating consequences - it is development in reverse. As civil wars have accumulated and persisted, they have generated or intensified a significant part of the global poverty problem that is the World Bank's core mission to confront. Part of the purpose of this Report is to alert the international community to the adverse consequences of civil war for development. These consequences are suffered mostly by civilians, often by children and by those in neighboring countries. Those who take the decisions to start or to sustain wars are often relatively immune to their adverse effects. The international community therefore has a legitimate role as an advocate for those who are victims. The second reason why the World Bank should focus on civil war is that development can be an effective instrument for conflict prevention. The risk of civil war is much higher in low-income countries than in middle-income countries. Civil war thus reflects not just a problem for development, but a failure of development. The research yields three main findings. First, civil wars have highly adverse ripple effects that are obviously not taken into account by those who determine whether they start or end. Second, the risks of civil war differ massively according to a country's characteristics, including its economic characteristics. As a result, there is a conflict trap, and civil war is becoming increasingly concentrated in relatively few developing countries. The third finding is that feasible international actions could substantially reduce the global incidence of civil war.Based on this research, the Report proposes a practical agenda for action.