As the Iraq and Afghanistan wars wind down, the U.S. military, like most other Western militaries, is enveloped in campaigns of reappraisal about what its role should be for the next few decades. The U.S. Navy and Air Force are developing the concepts of the Air-Sea Battle and Offshore Control, which are aimed essentially at countering the anti-access capabilities of nonstate, but especially state, adversaries. Since the unspoken focus of these concepts is on countries such as China or Iran, these are traditional military concerns and, to the extent that they facilitate the con-duct of expeditionary operations, they will necessarily involve the U.S. Army, too. But there can be little doubt about the general Western distaste for another major, land-centric conflict for the next decade or 2; nor, given the characteristics of China and Iran, would this make much strategic sense. Accordingly, the issue of what the U.S. Army's priorities should be for the next decade arises. Despite its probable institutional preference for a return to the land warfare-fighting ethos that preceded the current stress on counterterrorism operations, the Army is having to consider further engagement in irregular warfare and/or stability operations in its various guises. The so-called war on drugs will necessarily be a component of that much broader concept of future military operations, and from the U.S. Army's perspective, deserves reconsideration.1 Yet, such a focus elicits opposition, first from those who argue that the Army's greater engagement in the war on drugs would necessarily be an "exercise in futility" and, second, from the argument that this mission is already catered for sufficiently. Any further investment in times of budgetary constraint, it is argued, would undermine the Army's core warfighting capabilities. The issue evidently demands serious thought. This Book will argue, first, that the scale of the threat posed to Western security by the illicit trade in drugs is sufficiently serious to warrant both the label of a "war" (if with some reservations and caveats) and the extensive involvement of the military. It will then explore the extent, and the limitations, of the military contribution to the war on drugs. The Book will present some conclusions and a review of the implications of the war on drugs for the U.S. military of the 21st century.