This Chapter traces the historical developments of regulations on the use of force, beginning with the concepts of jus ad bellum and jus in bello through the crime of aggression. Despite the many human atrocities resulting from clear acts of aggression, attempts to legally regulate the use of force and to criminalize its perpetration have been largely unsuccessful. While great strides were made in the codification of international criminal law and accountability in the post-WWII era, it was not until the 2010 Kampala Amendments to the Rome Statute that the international community came to an agreed upon definition of aggression and still, its criminal prohibition remains uncertain. While legal developments on aggression have been slow, in part due to bureaucracy and realpolitik, there have been rapid advancements in weapons technology used to perpetuate acts of aggression. After exploring historical attempts to codify and proscribe the crime of aggression, this Chapter questions the future of aggression in light of the changing nature of warfare. This Chapter ultimately suggests that if the end goal is to deter engagement in aggression as a means of minimizing the resulting harm, the pursuit of alternative legal methods is the course of the future.