This book examines the implications of exponential technological change on the panoply of threats the US Air Force may have to face in the future and how the Air Force should posture itself to best deter those threats. Specifically, this book examines the changes in the array of threats for which be needed in the future, due to the proliferation of disruptive technologies explores the relevance of deterrence theory to both existing and new threats, some of which may surpass nuclear weapons in the risk they pose to both the United States and humankind; and recommends new ways of applying deterrence theory in order to reduce the risk that new disruptive technologies will be used against the United States or its interests. Building on previous Blue Horizons studies, this work assumes that science and technology growth will continue and will drive proliferation of advanced and potentially dangerous technologies. It posits that the result of rapid advances in nanotechnology, biotechnology, directed energy, space, computers and communications technologies may prove to be particularly dangerous. These developments span the private sector and many nations.1 Globalization in finance, communications, education, industry, trade governance, and myriad other areas is facilitating the rapid spread of new technologies among nations, groups, and individuals.2 Actors in unstable states and terrorists may use these technologies in malevolent ways to directly threaten US national security and that of friends and allies. This threat will take the Air Force back to its roots, which began in intelligence surveillance, and reconnaissance. Of principal concern by the year 2035 are threats in six separate areas nuclear weapons, attacks in cyberspace, directed energy weapons, space systems, nanotechnology, and biotechnology. Each of these poses the risk of catastrophic attack to the United States, its citizens, and its infrastructure. Deterring threats posed by nations, groups, and individuals will require new thinking regarding the application of deterrence theory. Fundamentally deterrence theory suggests that actors are deterred from attacking a target if they believe that the risk or cost of retribution outweighs the gains to be achieved by carrying out the attack. As such, deterrence theory has always contained two primary branches. One is deterrence by retribution the cost one can impose on the attacker for either carrying out an attack or making the attempt to do so. The other is deterrence by denial the ability to deny an adversary the opportunity to attack or having sufficient resiliency that little is to be gained even if the attack is successful. Each of these branches can affect the deterrence calculus. This book examines the interplay among the six technology threat areas and how deterrence theory applies.