This system, which was entensively followed by Darius, had on the whole good results, and was at any rate preferable to that barbarous policy of prudential fratricide which has prevailed widely in Oriental governments.
The system of checks, while it was effectual for the object at which it specially aimed, had one great disadvantage.

It weakened the hands of authority in times of difficulty.

When danger, internal or external, threatened, it was an evil that the powers of government should be divided, and the civil authority lodged in the hands of one officer, the military in those of another.

Concentration of power is needed for rapid and decisive action, for unity of purpose, and secrecy both of plan and of execution.

These considerations led to a modification of the original idea of satrapial government, which was adopted partially at first--in provinces especially exposed to danger, internal or external--but which ultimately became almost universal.