IX.6 On the defensive strength of states in general
For a state to be at full strength, its size must be such that there is a ratio between the speed with which an aggression can be carried out against it and the swiftness with which it can neutralize it. As the attacker can show up everywhere at once, the defender must also be able to show himself everywhere, and consequently the size of the state must be middling, so it can be proportional to the degree of speed which nature has given men for moving from one place to another.
France and Spain are precisely of the requisite size. The forces communicate so well that they can go immediately where they are needed ; the armies meet there and pass swiftly from one border to the next, and they have to fear none of the things that require a certain amount of time for execution.
In France, by wondrous luck, the capital is closer to the various borders precisely in proportion to their vulnerability ; and from there the prince sees each part of his country better the more exposed it is.
But when a vast state, such as Persia, is attacked, it takes several months for the scattered troops to assemble ; their march cannot be forced over so much time as it can for a fortnight. If the army that is on the border is defeated, it is surely dispersed, because its redoubts are not at hand. The victorious army, finding no resistance, advances in long marches, shows up before the capital, and sets siege to it, while the governors of the provinces can barely be notified to send relief. Those who judge the revolution imminent hasten it by refusing to obey. For men who are loyal only because punishment is at hand are no longer loyal when it is far away ; they advance their own private interests. The empire dissolves, the capital is taken, and the conqueror contests the provinces with the governors.
The true authority of a prince consists less in the ease with which he can conquer than the difficulty of attacking him, and, if I may put it this way, in the immutability of his situation. But the aggrandizement of states makes them reveal new sides by which they may be taken.
Thus, as monarchs must have wisdom to increase their authority, they must have at least as much prudence in order to limit it. While putting an end to the disadvantages of smallness, they must always keep an eye on the disadvantages of size.