The inherent advantages and potential payoffs of the terahertz (THz) regime for military and security applications serve as an important driver for interest in new THz-related science and technology. In particular, the very rapid growth in more recent years is arguably most closely linked to the potential payoffs of THz sensing and imaging (THz-S and u0026I).This book presents some of the leading fundamental research efforts towards the realization of practical THz-S and u0026I capabilities for military and security applications. Relevant subjects include theoretical prediction and or measurement of THz spectroscopic phenomenon in solid-state materials such as high explosives (e.g. HMX, PETN, RDX, TNT, etc.), carbon-fiber composites, biological agents (e.g. DNA, RNA, proteins, amino acids) and organic-semiconductor nanostructures. Individual papers also address the effective utilization of state-of-the-art THz-frequency technology in military and security relevant scenarios such as standoff S and u0026I, screening of packages and personnel, and perimeter defense. Technical papers introduce novel devices and or concepts that enhance THz source and detector performance, enabling completely new types of sensor functionality at THz frequency (e.g. detection at nanoscale molecular levels), and defining new and innovative sensing modalities (e.g. remote personnel identification) for defense and security. Therefore, the collective research presented here represents a valuable source of information on the evolving field of THz-S and u0026I for military and security applications.