The Achaemenians are enlightened despots who allow a certain amount of regional autonomy in the form of the satrapy system.

A satrapy is an administrative unit, usually organized on a geographical basis.

A satrap (governor) administer the region, a general supervises military recruitment and ensures order, and a state secretary keeps official records.

The general and the state secretary report directly to the central government.

The twenty satrapies are linked by a twenty-five hundred-kilometer highway, the most impressive stretch being the royal road from Susa to Sardis built by command of Darius I.

Relays of mounted couriers can reach the most remote areas in fifteen days.

As if to remind the satrapies of their limited independence, royal inspectors, the "eyes and ears of the king,"  tour the empire and report on local conditions.

Inclinations toward restiveness are further discouraged by the existence of the king's personal bodyguard of ten thousand men, called the Immortals.