History of the Peloponnesian War

The following spring, at its very commencement, the Lacedaemonians and their allies made a very early incursion into Attica, under the command of Agis son of Archidamus, king of the Lacedaemonians. In the first place, then, they ravaged the parts of the country about the plain, and then proceeded to fortify Decelea, dividing the work amongst the contingents of the different states.

The place is distant from the city of Athens about a hundred and twenty stades, and about the same, or not much more, from Boeotia. Now the fortress was raised for the annoyance of the plain and the richest parts of the country, being visible as far as Athens.