The doctrine of Kriegsraison, and its argument that ‘necessity knows no law’, is generally considered to have been laid to rest with the creation of the 1949 Geneva Conventions. However, this article asserts that Kriegsraison is resurrected and wholly alive in the USAs’ targeted killing programme. The targeted killing programme, now in existence for more than 15 years, remains one of the most problematic aspects of US anti-terror policy and continues to raise numerous legal questions. The article argues that treatment of the various legal frameworks relevant to targeted killing by the USA is suffused with Kriegsraison to such an extent that necessity, in its varying iterations, has become the primary guiding principle for US uses of force, and assessments as to their legality. This argument is predicated on an examination of the USAs’ expansive interpretation of jus ad bellum principles, its a-la-carte approach in recognising the applicability of jus in bello rules, and the designation of regions in which it uses force as lying ‘outside the area of active hostilities’. Throughout this assessment, parallels are drawn between the conduct of the USA today and between that of WWI-era Germany, which was characterised by Kriegsraison’s pervasive influence. Finally, the article contends that the use of armed drones as the primary tool for carrying out the targeted killing programme must be scrutinised, as this is vital to understanding the practical implementation of the Kriegsraison doctrine.