T
hroughout history, agreement between powerful leaders has been the most common strategy to prevent large-scale violence. This type of agreement, which we call an “elite pact,” does impose security for periods, but violence generally recurs. The immediate cause of the violence varies greatly by country, with many countries experiencing a combination of security, economic, and political stresses. These stresses may be internal (including low income or high inequality between groups) or they may be external (including global economic shocks, international drug trafficking, or the infiltration of foreign forces). This Report argues that in these environments, institutions and governance serve as an “immune system” and defense against stresses. When these stresses occur in societies with weak institutions and governance, violence often occurs. Reform is often difficult or impossible where violence is present. As a result, countries that fail to build legitimate institutions risk entering a vicious cycle of repeated violence and weak institutions. This chapter spells out what we know about this vicious cycle and why some countries are more vulnerable to violence than others.