Preventive Wars of Aggression: The Reconceptualization of National “Self-Defense”

This chapter examines the post-9/11 redefinition of preventive war in jus ad bellum. The chapter is divided into four sections. The first section explores how successive US administrations—from the George W. Bush to the Trump administrations—adopted a new definition of the concept of imminent threat and, consequently, introduced a new doctrine of preventive self-defense. The section shows how the US redefined an imminent threat by eliminating two of its key traditional components—namely, the immediacy and certainty of the threat. The second section examines how the new preventive war doctrine ignored two key principles governing the use of armed force, that is, the principles of necessity and proportionality. This section contends that the US enabled its military to conduct operations without observing these two key principles regulating the use of force. The third section explores which states, both US allies (e.g., the UK, Israel, Australia, Canada, India, and Turkey) and non-allies (e.g., Russia), adopted a similar doctrine of preventive national self-defense. This section provides an overview of political discourse (e.g., statements made by political leaders, policy papers) and state practice to determine which states embraced the new preventive war doctrine. The fourth section examines how the redefinition of preventive self-defense relaxed the rules on the use of armed force (e.g., a lower threshold for launching military operations, a broader temporal and geographical scope of war) and served as cover for the expansion of US state power.