Montesquieu

We have said that the sta­tes which the des­po­tic monarch conquers must be vas­sals. Historians outdo them­sel­ves prai­sing the gene­ro­sity of conque­rors who have res­to­red the crown to prin­ces they had defea­ted. The Romans were thus very gene­rous in crea­ting kings eve­ryw­here in order to have ins­tru­ments of ser­vi­tude.1 Such a move is a neces­sary act. If the conque­ror keeps the conque­red state, the gover­nors he sends will not be able to contain their sub­jects, nor he his gover­nors. He will be obli­ged to dis­place troops from his for­mer patri­mony to secure the new one. All the mis­for­tu­nes of the two sta­tes will be sha­red ; the civil war of the one will be the civil war of the other. Now if, on the contrary, the conque­ror returns the throne to the legi­ti­mate prince, he will have a neces­sary ally, who with his own for­ces will sup­ple­ment his. We have just seen Shah Nadir conquer the trea­su­res of the Mogol and leave him Hindustan.

Ut haberent instrumenta servitutis et reges [‘They held even kings to be instruments of servitude’].