Thucydides

The fate of those of their neighbours who had already rebelled and had been subdued was no lesson to them; their own prosperity could not dissuade them from affronting danger; but blindly confident in the future, and full of hopes beyond their power though not beyond their ambition, they declared war and made their decision to prefer might to right, their attack being determined not by provocation but by the moment which seemed propitious. The truth is that great good fortune coming suddenly and unexpectedly tends to make a people insolent; in most cases it is safer for mankind to have success in reason than out of reason; and it is easier for them, one may say, to stave off adversity than to preserve prosperity.

speculation is carried on in safety, but, when it comes to action, fear causes failure.

Hope, danger's comforter...

[A]nd their judgment was based more upon blind wishing than upon any sound prediction; for it is a habit of mankind to entrust to careless hope what they long for, and to use sovereign reason to thrust aside what they do not desire.

We hope that you, instead of thinking to influence us by saying that you did not join the Lacedaemonians, although their colonists, or that you have done us no wrong, will aim at what is feasible, holding in view the real sentiments of us both; since you know as well as we do that right, as the world goes, is only in question between equals in power, while the strong do what they can and the weak suffer what they must.

That war is an evil is a proposition so familiar to every one that it would be tedious to develop it. No one is forced to engage in it by ignorance, or kept out of it by fear, if he fancies there is anything to be gained by it.

We must march against the enemy, and teach him that he must go and get what he wants by attacking someone who will not resist him, but that men whose glory it is to be always ready to give battle for the liberty of their own country, and never unjustly to enslave that of others, will not let him go without a struggle.

[T]hey possess most gold and silver, by which war, like everything else, flourishes.

Of the gods we believe, and of men we know, that by a necessary law of their nature they rule wherever they can.

Let him remember that many before now have tried to chastise a wrongdoer, and failing to punish their enemy have not even saved themselves; while many who have trusted in force to gain an advantage, instead of gaining anything more, have been doomed to lose what they had. Vengeance is not necessarily successful because wrong has been done, or strength sure because it is confident; but the incalculable element in the future exercises the widest influence, and is the most treacherous, and yet in fact the most useful of all things, as it frightens us all equally, and thus makes us consider before attacking each other.

The secret of happiness is freedom and the secret of freedom is courage.

In practice we always base our preparations against an enemy on the assumption that his plans are good; indeed, it is right to rest our hopes not on a belief in his blunders, but on the soundness of our provisions. Nor ought we to believe that there is much difference between man and man, but to think that the superiority lies with him who is reared in the severest school.