I will not omit to remind a prince who has newly taken a state with the secret help of its inhabitants, that he must consider well the motives that have induced those who have favoured him to do so, and if it is not natural affection for him, but only because they were not contented with the state as it was, he will have great trouble and difficulty in maintaining their friendship, because it will be impossible for him to content them. And on well examining the cause of this in the examples drawn from ancient and modern times it will be seen that it is much easier to gain the friendship, of those men who were contented with the previous condition and were therefore at first enemies, than that of those who not being contented, became his friends and helped him to occupy it. It has been the custom of princes in order to be able to hold securely their state, to erect fortresses, as a bridle and bit to those who have designs against them, and in order to have a secure refuge against a sudden assault. I approve this method, because it was anciently used. Nevertheless, Messer Niccolo Vitelli has been seen in our own time to destroy two fortresses in Città di Castello in order to keep that state. Guid' Ubaldo, Duke of Urbino, on returning to his dominions from which he had been driven by Cesare Borgia, razed to their foundations all the fortresses of that province, and considered that without them it would be more difficult for him to lose again the state. The Bentivogli, in returning to Bologna, used similar measures. Therefore fortresses may or may not be useful according to the times; if they do good in one way, they do harm in another.