Field Manual (FM) 3-37 provides doctrinal guidance for commanders and staffs who are responsible for planning and executing protection in support of full spectrum operations. It describes protection as both an element of combat power and as a warfighting function. FM 3-37 corresponds with Army operations doctrine introduced in the FM 3-0 capstone manual. As the Army keystone manual for protection, FM 3-37 will help commanders understand and visualize protection concepts and ideas and enable them to describe protection tasks and systems for integration into the operations process. FM 3-37 expands on the protection and combined arms terminology outlined in FM 3-0. It explains how protection can be achieved and applied through the combination and integration of reinforcement and complementary capabilities to preserve combat power or to protect personnel, physical assets, or information. This manual recognizes that protection has no direct antecedent from the former battlefield operating systems, so protection is realized in many ways. Therefore, the text introduces the five forms and five principles of protection to provide a context for battle command and a framework for task assignment: Forms of protection: Deterrence; Prevention; Active security; Passive defense; Mitigation. Principles of protection: Full-dimension; Integrated; Layered; Redundant; Enduring.