How did king darius rule the persian empire

 Darius claimed his empire extended from the Sakas beyond Sogdiana to the Kush, and from Sind to Sardis. Satrapies had been used by his predecessors, but Darius refined the process. He divided his empire into 20 of them and added security measures to reduce revolt. He was responsible for the Persian Empire's capital at Persepolis and for many other building projects, including: Roads through his empire (notably the Royal Road with messengers stationed along it so no one man had to ride more than a day to deliver the post). As king of Egypt in the Late Period, he was known as a law-giver, and for completing a canal from the Nile to the Red Sea. He was also renowned for irrigation (qanat) projects), and a coinage systems. Darius had at least 18 children. His successor, Xerxes, was the oldest son of his first wife, Atossa, making Xerxes a grandson of Cyrus the Great. Darius and his son Xerxes are associated with the Greco-Persian or Persian Wars. The last king of the Achaemenid Dynasty was Darius III, who ruled from 336 - 330 B.C. Darius III was a descendant of Darius II (ruled 423-405 B.C.), who was a descendant of King Darius I.