Pre-medieval Europe
Ancient Greece
In Ancient Greece, publicly owned slaves were used by magistrates as police. In Athens, a group of 300 Scythian slaves was used to guard public meetings to keep order and for crowd control, and also assisted with dealing with criminals, handling prisoners, and making arrests. Other duties associated with modern policing, such as investigating crimes, were left to the citizens themselves.[11]
Roman Empire
In most of the Empire, the Army, rather than a dedicated police organization, provided security. Local watchmen were hired by cities to provide some extra security. In Rome itself, the Urban Cohorts were responsible for law and order and acted as a dedicated police force. Magistrates such as Procurator Fiscals and quaestors investigated crimes. There was no concept of public prosecution, so victims of crime or their families had to organize and manage the prosecution themselves.
Before its decline, the Roman Empire had a relatively effective law enforcement system. Under the reign of Augustus, when the capital had grown to almost one million inhabitants, 14 wards were created; the wards were protected by seven squads of 1,000 men called "Vigiles", who guarded against fires and served as nightwatchmen. If necessary, the Vigiles might call the Praetorian Guard for assistance. Beginning in the 5th century, policing became a function of clan chiefs and heads of state.