The attacks of September 11 tragically reawakened the United States to the fact that the world is a hazardous place deserving renewed vigilance and a proactive foreign policy. Not only must the United States combat the threat of global terrorism, it must prepare for other dangerous foes who will be spawned by the chaos of disintegrating political regimes or sponsored by new forces rising in power. State or non-state, future enemies will be empowered by the same global trends that give terrorists access to fluid financing, decisive information, freedom of movement, and the possibility of wielding weapons of mass destruction. A few state-centered adversaries of the future (and there will be some—the death of the state and Thucydidian politics has been greatly exaggerated) might challenge the United States on roughly familiar terms of battle—ones for which America is prepared. More likely, future foes will change the rules, style, and modalities of warfare so as to strip the United States of its overwhelming advantage in conventional warfare. Non-state enemies, of which there will be many more than just Osama bin Laden, will certainly choose this latter course of action. The threats will be global and amorphous, changing form and tactics frequently while seeking constantly to increase their lethality and attack states where they are weakest. As the September 11 attacks horribly demonstrated, the wars of the future will likely contain no front lines, and America’s foes will make little distinction between combatant and civilian….