Montesquieu
 

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.