Two competing theories vie for dominance regarding the relationship between the U.S. military and the natural environment. On the one hand, because legal rules permit the military to disregard environmental laws when they conflict with the military’s national security mission, one might be left with the impression that the military’s mission conflicts inexorably with environmental protection. Yet, the military is currently engaged in an extensive undertaking to improve its sustainable energy use by reducing demand for fossil fuels and developing renewable energy sources. The military is undertaking such actions not only in response to congressional directives and presidential executive orders, but also voluntarily in response to its operational and national security needs. In some cases, the military is leveraging private financing rather than taxpayer funds to drive innovation. Such cooperation among the military, private financiers, and technology firms has the potential to transform for the better not only our nation’s energy profile, but also the militaryindustrial complex. This new Military-Environmental Complex should become a factor in the debate over regulatory instruments to combat climate change. At the same time, however, these relationships warrant some caution to prevent rent-seeking.