A prince... must learn from the fox and the lion... One must be a fox in order to recognize traps, and a lion to frighten off wolves. Those who act simply as lions are stupid. So it follows that a prudent ruler cannot, and must not, honour his word when it places him at a disadvantage and when the reasons for which he made his promise no longer exist.
Niccolo MachiavelliI am firmly convinced, therefore, that to set up a republic which is to last a long time, the way to set about it is to constitute it as Sparta and Venice were constituted; to place it in a strong position, and so to fortify it that no one will dream of taking it by a sudden assault; and, on the other hand, not to make it so large as to appear formidable to its neighbors. It should in this way be able to enjoy its form of government for a long time. For war is made on a commonwealth for two reasons: to subjugate it, and for fear of being subjugated by it.
Niccolo MachiavelliAnd above all you ought to guard against leading an army to fight which is afraid or which is not confident of victory. For the greatest sign of an impending loss is when one does not believe one can win.
Niccolo Machiavelli