A Town Watch is an organized group of civilians devoted to crime- and vandalism-prevention. The Town watch were featured as one of the primary units in Rome: Total War.
Upon being a "peace-keeping" force, the Town Watch is tasked to provide assistance to the security and stability of each town, city and village.
The idea around the Town watch began with the modern day American System "neighborhood watch" which also aims to similar tasks to the standard Town Watch.