History of the Peloponnesian War

"Here, then, let your dilatoriness end; at this moment succour both the Potidaeans and the rest of your allies, as you promised to do, by invading Attica without delay, that you may not betray your friends and kinsmen to their bitterest enemies, and drive the rest of us in despair to seek some other alliance.

If we took such a course we should be committing no wrong either in the sight of the gods we have sworn by or of men of understanding; for treaties are broken not by those who when left unsupported join others, but by those who fail to succour allies they have sworn to aid. But if you mean to be zealous allies we will stay;