The Peace of Westphalia occasioned a flurry of works devoted to ius gentium – the so-called “later classics” of the seventeenth and eighteenth centuries – where this subject was developed in ways that sometimes departed significantly from the models established by the founding fathers. Their approaches can be sorted into three different groups depending on how they conceive the relation between natural and positive law. These groups can be identified as follows: we have (1) thinkers who foreground the role of positive law, pushing natural law into the background; (2) thinkers who instead foreground natural law (Samuel Pufendorf); and (3) thinkers who attempt to work the two into a synthesis (Emer de Vattel). But there is one feature these authors all have in common, regardless of how they work out the relation between natural law and positive law, and it is that they all move beyond the doctrine of just war and the nondiscriminating conception of war as a clash between parties that stand on an equal moral and legal footing.