Already in the seventeenth century, Hugo Grotius' book "De jure belli ac pacis" laid the foundation for a normative theory of international relations. Nevertheless, political philosophy remained largely focused on justifying state power over its own citizens until the twentieth century. It took the profound upheavals of two world wars and an awareness of the global threat posed by nuclear armament for international relations to regain prominence in political philosophy during the Vietnam War. To this day, an intense discussion has developed that encompasses not only issues of military force but also numerous other areas. Frank Dietrich and Véronique Zanetti illuminate some of these topics in this introduction from a systematic perspective.