Military Police. A branch in the US Army, but usually used to describe the soldiers of that same branch. They are tasked with a dual mission: In garrison, they act in a law and order capacity, performing guard duties as well as Community Law Enforcement (CLE). In their wartime mission, they engage in MSR recon, MSR security (aka. combat patrols - seek and destroy enemies/IEDs along Main Supply Routes,) and convoy security.
The MPs are never around when I need one, and always around when I don't!