ABSTRACT
This chapter introduces one of the seminal figures in the historical development of the just war tradition: Emer de Vattel. Constitutive of the modern natural law tradition, Vattel's Law of Nations had profound ramifications for just war thinking: it provided a blueprint for international conduct and diplomacy as we have come to know it today. While Grotius's work is generally considered groundbreaking in establishing the conduct of states as sovereign actors, Vattel's treatise was far more expansive in its scope and detailed in affirming the rules of engagement not only in times of war but also in times of peace. To understand the justice of war for Vattel, one must begin with the general ties that bind states together – the law of nations. Vattel does not really explore who defines the natural law in the first place, perhaps assuming that humanity's laws are automatically in line with broader European values.
