The United States has been developing space for many years, and satellites provide the US Military with an unparalleled advantage over its adversaries. Constellations of both military and civilian satellites provide protection and support for military operations; deliver ballistic missile early warning; supply reliable, secure and jam-proof communications; gather audio-visual intelligence; predict weather patterns; guide navigation; and deliver guided-weapons targeting, as well as a host of other missions. This book explores the design, development and usage of US military space systems, as well as, past and future threats to the systems. The current relevance of this topic to the international community as a whole is key, as space becomes the next, if only virtual, theater of warfare.