Legal Definition of Armed force: A posse; a group of armed civilians authorized by the official peace officers of the community to aid in the capture of criminals and the prevention of crime | Learn about the legal definition of armed force, also known as a posse, and how it aids law enforcement in capturing criminals and preventing crime. Discover examples of a posse in action and the importance it holds in maintaining public safety. Find out how a posse helps bridge the gap between limited resources and effective crime prevention, acting as a deterrent to potential criminals