It complemented the Hellenic Gendarmerie, which was responsible for rural and suburban areas.

The force became operational in the city of Corfu in 1920, followed by Patras (1921), Piraeus (1923) and Athens (1929).

Remarkably, in Thessaloniki, Greece's second largest city, the force was not established due to the Gendarmerie's opposition, despite the law's provisions.

Unlike the paramilitary Gendarmerie, which had close ties to the Hellenic Army and was commanded by Army generals, the Cities Police was a purely civilian force, modeled after the Metropolitan Police of London, and with training provided by a British mission under Sir Frederick Loch Halliday.

[1] From the late 1920s, the Cities Police, and especially its feared General Security Directorate, initiated the state persecution of the nascent Communist Party of Greece (KKE), whose popularity was growing among the urban poor, the working classes and the destitute refugees from Asia Minor.