The advancement of human enhancement technologies is leading to deep strategic debate among some military think tanks. The widespread investment in enhancement research leaves little doubt that different jurisdictions worldwide can envisage the direct national strategic opportunity, and threat, of enhanced military personnel in combat situations. Such an opportunity, and such a combative threat, may pre-empt ethical concerns. Armed forces may have no choice but to develop such technologies, and rapidly, because other nations are already doing so. However for the first time in the history of our species, we are being challenged on what it is to be – or to remain – a human.