Darius I Darius the Great was the king of Persia from 522–486 BC. He was one of the greatest rulers of the Achaemenid dynasty and was distinguished for his administrative genius and great building projects. The main achievement of Darius was consolidation and organization. After putting down numerous rebellions in his earlier years, Darius set out to administer his kingdom. He minted gold coins, called Darics that were widely used for commerce and trade. He divided the Empire up into twenty provinces, each run by a satrap, or governor, who in most cases, had a great deal of autonomy. In order to gain the good will of his subjected people, he allowed religious freedom, and donated money toward the building of various temples, including the Temple of Jerusalem, in Judea. Darius also started use of a Royal Road that allowed messages, soldiers, and mail to be sent quickly across the empire. He promoted trade and business and established a law code.
After the death of Darius his son Xerxes became ruler. Darius left an overwhelming responsibility filled with high demands to keep things in order. I believe that Xerxes did a solid job maintain the system that was in place. After the death of Xerxes (486-464 B.C.E.), the Persian Empire lacked that strong hand. As a result, various problems developed that fed back upon one another and led to Persia's decline and fall. For one thing, weak rulers led to numerous provincial revolts, especially in Egypt, which always had detested Persian rule. Secondly, the provincial satraps also became more independent, ruling their satrapies more as kings than as the king's loyal subjects. They even carried on their own foreign policies and waged war on each other, which only added to Persia's problems.
Revolts and unruly satraps caused serious economic problems for the empire. Persian taxes became heavier and more oppressive, which led to economic depression and revolts, which in turn led to more repression, heavier taxes and so on. The Persian kings also started hoarding gold and silver rather than re-circulating it. This created economic turmoil without enough gold and silver for doing business. As a result of this economic turmoil, the Persian kings got weaker still, which fed back into the problem of revolts and powerful satraps and so on. In retrospect, I believe that the system that was implemented by Darius was of a standard that only he could sustain. His fearful ruler ship allowed him to be in total control at all times. His arrogant nature insured that he would be recognized praised for good work. His successor did not have a stout character that was needed to uphold the system implemented by Darius. Without a strong leader the Persian Empire was too strong for itself, leading to its own demise.