Montesquieu
 

IX.8 A case where the defensive strength of a state is inferior to its offensive strength

It was Sir de Coucy who said to King Charles V that “the English are never so weak nor so easy to defeat as at home.” That is what was said of the Romans ; it is what the Carthaginians expe­rien­ced ; it is what will befall every power which has sent its armies far afield to unite by the strength of dis­ci­pline and mili­tary power peo­ple who are divi­ded at home by poli­ti­cal or civil inte­rests. The state is weak because of the disease that is still pre­sent, and it has been fur­ther wea­ke­ned by the remedy.

Sir de Coucy’s maxim is an excep­tion to the gene­ral rule that one should not under­take far-flung wars. And this excep­tion indeed confirms the rule, since it is valid only against those who have them­sel­ves under­ta­ken them.