History of the Peloponnesian War

And for a short time the confederacy held together; but afterwards the Lacedaemonians and Athenians, having quarrelled, waged war against each other with their allies: and of the rest of the Greeks, whoever in any quarter were at variance, now betook themselves to these. So that, from the Persian war all the time to this, making peace at one time, and at another war, either with each other or with their own revolting allies, they prepared themselves well in military matters, and became more experienced from going through their training in scenes of danger. [*]( Their field of exercise was not the parade, but the field of battle. —Arnold.)