During the last twenty years military explosives, and energetic materials in general, have changed significantly. Worldwide, research and development programs are active in developing promising insensitive HEMs with higher performance. This has been due to several factors, which include new operational requirements such as Insensitive Munitions (IM), but it is also due to the availability of new materials and to new assessment and modelling techniques. The present review focuses on the basic idea and necessity for IM, and the conditions, technical requirements and tests for IM. The review also explains the various promising insensitive high explosives, their synthesis and formulation used in different propellants.