and when he did come they had no walls to stop him), - Thucydides

For these reasons they should not hesitate to exchange peace for war. If wise men remain quiet, while they are not injured, brave men abandon peace for war when they are injured, returning to an understanding on a favourable opportunity: in fact, they are neither intoxicated by their success in war, nor disposed to take an injury for the sake of the delightful tranquility of peace. Indeed, to falter for the sake of such delights is, if you remain inactive, the quickest way of losing the sweets of repose to which you cling; while to conceive extravagant pretensions from success in war is to forget how hollow is the confidence by which you are elated.

Words had to change their ordinary meaning and to take that which was now given them. Reckless audacity came to be considered the courage of a loyal ally; prudent hesitation, specious cowardice; moderation was held to be a cloak for unmanliness; ability to see all sides of a question, inaptness to act on any. Frantic violence became the attribute of manliness; cautious plotting, a justifiable means of self-defence. The advocate of extreme measures was always trustworthy; his opponent a man to be suspected. To succeed in a plot was to have a shrewd head, to divine a plot a still shrewder; but to try to provide against having to do either was to break up your party and to be afraid of your adversaries.

But his (Pericles’) successors were more on an equality with one another, and, each one struggling to be first himself, they were ready to sacrifice the whole conduct of affairs to the whims of the people.

Such weakness in a great and imperial city led to many errors, of which the greatest was the Sicilian expedition; not that the Athenians miscalculated their enemy's power, but they themselves, instead of consulting for the interests of the expedition which they had sent out, were occupied in intriguing against one another for the leadership of the democracy, and not only hampered the operations of the army, but became embroiled, for the first time, at home.

And yet after they had lost in the Sicilian expedition the greater part of their fleet and army, and were now distracted by revolution, still they held out three years not only against their former enemies, but against the Sicilians who had combined with them, and against most of their own allies who had risen in revolt. Even when Cyrus the son of the King joined in the war and supplied the Peloponnesian fleet with money, they continued to resist, and were at last overthrown, not by their enemies, but by themselves and their own internal dissensions.

(Book 2 Chapter 65.10-12)