Thus, what was gained by the new system was not so much the relief of the subject from uncertain taxation as the advantage to the crown of knowing beforehand what the revenue would be, and being able to regulate its expenditure accordingly. Still a certain amount of benefit did undoubtedly accrue to the provincials from the system; since it gave them the crown for their protector. So long as the payments made to the state were irregular, it was, or at least seemed to be, for the interest of the crown to obtain from each province as much as it could anyhow pay. When the state dues were once fixed, as the crown gained nothing by the rapacity of its officers, but rather lost, since the province became exhausted, it was interested in checking greed, and seeing that the provinces were administered by wise and good satraps. The control of its great officers is always the main difficulty of a despotic government, when it is extended over a large space of territory and embraces many millions of men. The system devised by Darius for checking and controlling his satraps was probably the best that has ever yet been brought into operation. His plan was to establish in every province at least three officers holding their authority directly from the crown, and only responsible to it, who would therefore act as checks one upon another. These were the satrap, the military commandant, and the secretary. The satrap was charged with the civil administration, and especially with the department of finance. The commandant was supreme over the troops. The office of the secretary is less clearly defined; but it probably consisted mainly in keeping the Court informed by despatches of all that went on in the province. Thus, if the satrap were inclined to revolt, he had, in the first place, to persuade the commandant, who would naturally think that, if he ran the risk, it might as well be for himself; and, further, he had to escape the lynx eyes of the secretary, whose general right of superintendence gave him entrance everywhere, and whose prospects of advancement would probably depend a good deal upon the diligence and success with which he discharged the office of “King’s Eye” and “Ear.” So, if the commandant were ambitious of independent sway, he must persuade the satrap, or he would have no money to pay his troops; and he too must blind the secretary, or else bribe him into silence. As for the secretary, having neither men nor money at his command, it was impossible that he should think of rebellion.