Niccolo Machiavelli - Discourses on the First Decade of Titus Livius (Chap. 1.43) lyrics

That Men fighting in their own Cause make good and resolute Soldiers. From what has been touched upon above, we are also led to remark how wide is the difference between an army which, having no ground for discontent, fights in its own cause, and one which, being discontented, fights to satisfy the ambition of others. For whereas the Romans were always victorious under the consuls, under the decemvirs they were always defeated. This helps us to understand why it is that mercenary troops are worthless; namely, that they have no incitement to keep them true to you beyond the pittance which you pay them, which neither is nor can be a sufficient motive for such fidelity and devotion as would make them willing to die in your behalf. But in those armies in which there exists not such an attachment towards him for whom they fight as makes them devoted to his cause, there never will be valour enough to withstand an enemy if only he be a little brave. And since such attachment and devotion cannot be looked for from any save your own subjects, you must, if you would preserve your dominions, or maintain your commonwealth or kingdom, arm the natives of your country; as we see to have been done by all those who have achieved great things in war. Under the decemvirs the ancient valour of the Roman soldiers had in no degree abated; yet, because they were no longer animated by the same good will, they did not exert themselves as they were wont. But so soon as the decemvirate came to an end, and the soldiers began once more to fight as free men, the old spirit was reawakened, and, as a consequence, their enterprises, according to former usage, were brought to a successful close.