Whether fortresses and many other expedients that princes commonly employ are useful or not
A prince has many options in terms of preserving his state. Some are useful while others are not. Machiavelli concedes that each case should be evaluated within its own context, nevertheless, he attempts to offer some general advice. First, it is always necessary for a new prince to arm his subjects. But when a prince adds a new domain to his original possession, he must disarm his new subjects because he should rely only on the soldiers from his native domain. Second, it is not wise for a prince to encourage factions within his own state.
It serves him better to rid himself of one side than to allow disunity. Third, for a new prince, it is often wise to rely on subjects he is suspicious of in the beginning of his reign than others. The suspicious subjects, knowing that they are under scrutiny, are more inclined to please him in order to gain the prince's favor. Also, a prince who acquires a new state with the aid of its inhabitants must judge their motives-whether they helped because of their natural affection for the prince or because of their hatred for the former ruler. A prince cannot trust those of the latter because it is impossible to satisfy them. It is better for him to reconcile with his former enemies. Last, Machiavelli considers fortresses useful in certain cases and harmful in others. Ultimately, a prince should not rely too heavily on fortresses because they are useless if the people hate him.
