As shown in this chapter, state capacity and security warranties are further key factors in the peace formula. In particular, besides certain institutional features, the overall strength of the state is a major determinant of political stability, as illustrated by examples and recent research on Iraq, Somalia, Niger and the origins of the Mafia in southern Italy. Drawing on cutting-edge studies, it is argued that being feared (by extremist groups) may be more important than being loved (by the population at large). In order to win the hearts and minds of the population, it is essential that first public safety is guaranteed and that basic services are delivered efficiently. This is easier said than done. It is shown that when foreign military aid aims at capacity building, it often backfires. In contrast, UN peacekeeping troops have been demonstrated to play a key role. We end this chapter by emphasizing the several domestic factors that can help the building of lasting state capacity, with a special emphasis on well-designed welfare programs such as Franklin D. Roosevelt’s New Deal.