History of the Peloponnesian War

Upon this the Peloponnesians, desirous of aiding the Aeginetans, threw into Aegina a force of three hundred heavy infantry, who had before been serving with the Corinthians and Epidaurians. Meanwhile the Corinthians and their allies occupied the heights of Geraneia, and marched down into the Megarid, in the belief that with a large force absent in Aegina and Egypt, Athens would be unable to help the Megarians without raising the siege of Aegina.

But the Athenians, instead of moving the army of Aegina, raised a force of the old and young men that had been left in the city, and marched into the Megarid under the command of Myronides.