Threat in the national security context can be defined as state or non-state actor actions that can cause disruption, damage and potential ruin of another state’s national security, economic, defence and political stability and/or sovereignty. Threats must be assessed against an adversary’s intent, opportunity and capability. Clearly assessment is as much art as it is science and must be considered within the context of an ambiguous, dynamic and extremely complex security environment. Response to threat(s) must be calibrated accordingly. This volume examines threat through three different lenses: historical, from a macro perspective of “below the threshold of armed conflict” to more specific threats, and finally, potential SOF/SO responses to the myriad of existing and emerging threats that face partner nations.