The U.S. Air Force is said to be evolving into an Air and Space Force on its way to becoming a Space and Air Force. Part of this transition includes the possibility of deploying weapons in space. While much has been written about the need for weapons in space, or conversely the need to keep space as a sanctuary, little has been published about what space-based weapons can and cannot bring to the battlefield. A decision to put weapons in space, or to refrain from doing so, should be based on a firm foundation of knowledge about what the weapons can be expected to do. Numerous concepts have been advocated as natural evolutions of surface and airborne weapons; it is critical to examine how these orbital weapons compare with their terrestrial counterparts. This book evaluates the theoretical capabilities of orbital weapons and compares them to weapons already in existence and concepts proposed for development. The objective of this book is to provide insight into where future investments should be made if the United States is to protect its increasingly important space-based assets, and retain its position as a global leader able to project military power wherever necessary.