History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
and sea. And, indeed, the Locrians had at this same time invaded the territory of the Rhegians with all their forces in order to prevent them from giving any aid to the Messenians; and, besides, some Rhegians who were living in exile among the Locrians also urged them to make the invasion; for Rhegium had for a long time been in a state of revolution, and it was impossible at the moment to make any defence against the Locrians, who were consequently the more eager
to attack. The Locrians first ravaged the country and then withdrew their land forces, but their ships continued guarding Messene; and still other ships were now being manned to be stationed at Messene and to carry on war from there.
About the same time that spring, before the grain was ripe, the Peloponnesians and their allies made an invasion of Attica, under the command of Agis son of Archidamus, king of the Lacedaemonians; and encamping there they ravaged the land.