Niccolò Machiavelli
Discourses on the First Decade of Titus Livius (Chap. 2.9)
Of the Causes which commonly give rise to Wars between States.

The occasion which led to war between the Romans and Samnites, who for long had been in league with one another, is of common occurrence in all powerful States, being either brought about by accident, or else purposely contrived by some one who would set war a-foot. As between the Romans and the Samnites, the occasion of war was accidental. For in making war upon the Sidicinians and afterwards on the Campanians, the Samnites had no thought of involving themselves with the Romans. But the Campanians being overpowered, and, contrary to the expectation of Romans and Samnites alike, resorting to Rome for aid, the Romans, on whose protection they threw themselves, were forced to succour them as dependants, and to accept a war which, it seemed to them, they could not with honour decline. For though they might have thought it unreasonable to be called on to defend the Campanians as friends against their own friends the Samnites, it seemed to them shameful not to defend them as subjects, or as a people who had placed themselves under their protection. For they reasoned that to decline their defence would close the gate against all others who at any future time might desire to submit themselves to their power. And, accordingly, since glory and empire, and not peace, were the ends which they always had in view, it became impossible for them to refuse this protectorship.

A similar circumstance gave rise to the first war with the Carthaginians, namely the protectorate assumed by the Romans of the citizens of Messina in Sicily, and this likewise came about by chance. But the second war with Carthage was not the result of chance. For Hannibal the Carthaginian general attacked the Saguntans, who were the friends of Rome in Spain, not from any desire to injure them, but in order to set the arms of Rome in motion, and so gain an opportunity of engaging the Romans in a war, and passing on into Italy. This method of picking a quarrel is constantly resorted to by powerful States when they are bound by scruples of honour or like considerations. For if I desire to make war on a prince with whom I am under an ancient and binding treaty, I shall find some colour or pretext for attacking the friend of that prince, very well knowing that when I attack his friend, either the prince will resent it, when my scheme for engaging him in war will be realized; or that, should he not resent it, his weakness or baseness in not defending one who is under his protection will be made apparent; either of which alternatives will discredit him, and further my designs.

We are to note, therefore, in connection with this submission of the Campanians, what has just now been said as to provoking another power to war; and also the remedy open to a State which, being unequal to its own defence, is prepared to go all lengths to ruin its assailant,—that remedy being to give itself up unreservedly to some one whom it selects for its defender; as the Campanians gave themselves up to the Romans, and as the Florentines gave themselves up to King Robert of Naples, who, after refusing to defend them as his friends against Castruccio of Lucca by whom they were hard pressed, defended them as his subjects.