The desire for humanity and the desire for security have co-existed as long as humans have been alive. As science has become increasingly sophisticated, so have the methods of self-defence by States. Nanotechnology is already changing warfare by increasing capabilities upon which armed forces are heavily reliant: more efficient energy storage, advanced photovoltaics, and improved military protective equipment to name a few of these developments. Some applications of nanomaterials by the military are both powerful and subtle, and have neurological and biological applications: 'devices that can infiltrate electronics and seize control at crucial moments, artificial disease agents that can rest harmlessly in victims' bodies until activated by an external signal'. The advance of the use or contemplation of use of these types of nanoscale applications by the military requires urgent analysis in light of existing international law, particularly in light of their potential effects on humans and on the environment.