Live and Learn

I had always thought that Niccolo Machiavelli had said that exiles were never to be trusted in his seminal work on governance, The Prince.

I was wrong, it was from his book, Discourses on the First Decade of Titus Livius, Specifically in Chapter XXXI of Book II, "Of the Danger of trusting banished Men."

I've only started reading the book, but his outlook on ancient history is remarkably modern, or perhaps I should say that it is timeless:

The danger of trusting those who are in exile from their own country, being one to which the rulers of States are often exposed, may, I think, be fitly considered in these Discourses; and I notice it the more willingly, because I am able to illustrate it by a memorable instance which Titus Livius, though with another purpose, relates in his history. When Alexander the Great passed with his army into Asia, his brother-in-law and uncle, Alexander of Epirus, came with another army into Italy, being invited thither by the banished Lucanians, who gave him to believe that, with their aid, he might get possession of the whole of that country. But when, confiding in the promises of these exiles, and fed by the hopes they held out to him, he came into Italy, they put him to death, their fellow-citizens having offered to restore them to their country upon this condition. It behoves us, therefore, to remember how empty are the promises, and how doubtful the faith, of men in banishment from their native land. For as to their faith, it may be assumed that whenever they can effect their return by other means than yours, notwithstanding any covenants they may have made with you, they will throw you over, and take part with their countrymen. And as for the empty promises and delusive hopes which they set before you, so extreme is their desire to return home that they naturally believe many things which are untrue, and designedly misrepresent many others; so that between their beliefs and what they say they believe, they fill you with false impressions, on which if you build, your labour is in vain, and you are led to engage in enterprises from which nothing but ruin can result.

To this instance of Alexander I shall add only one other, that, namely, of Themistocles the Athenian, who, being proclaimed a traitor, fled into Asia to Darius, to whom he made such lavish promises if he would only attack Greece, that he induced him to undertake the enterprise. But afterwards, when he could not fulfil what he had promised, either from shame, or through fear of punishment, he poisoned himself. But, if such a mistake as this was made by a man like Themistocles, we may reckon that mistakes still greater will be made by those who, being of a feebler nature, suffer themselves to be more completely swayed by their feelings and wishes Wherefore, let a prince be careful how he embarks in any enterprise on the representations of an exile; for otherwise, he is likely either to be put to shame, or to incur the gravest calamities.

Because towns are sometimes, though seldom, taken by craft, through secret practices had with their inhabitants, I think it not out of place to discuss the matter in the following Chapter, wherein I shall likewise show in how many ways the Romans were wont to make such acquisitions. 

Credit to Project Gutenberg for the making translation available online.