Darius reorganized his empire by dividing them into twenty provinces called the "satrapies," headed by leaders, picked by Darius himself, called the "satraps."
A secretary was assigned in each of the satraps to observe the state affairs and communicate the events with Darius, while a garrison commander was responsible for the troops. A commission was responsible for the evaluation of the expenses and revenues of each of the satraps, while a treasurer safeguarded the provincial revenues. More importantly, a network of royal inspectors called the "EYES AND THE EARS OF THE KING" were established by Darius to do further checks on the satraps.