History of the Peloponnesian War

There is, however, no advantage in reflections on the past further than may be of service to the present. For the future we must provide by maintaining what the present gives us and redoubling our efforts; it is hereditary to us to win virtue as the fruit of labour, and you must not change the habit, even though you should have a slight advantage in wealth and resources; for it is not right that what was won in want should be lost in plenty. No, we must boldly advance to the war for many reasons; the god has commanded it and promised to be with us, and the rest of Hellas will all join in the struggle, part from fear, part from interest.

You will not be the first to break a treaty which the god, in advising us to go to war, judges to be violated already, but rather to support a treaty that has been outraged: indeed, treaties are broken not by resistance but by aggression.