But Pyrrhus now overran Thessaly and was seen as far south as Thermopylae; Demetrius therefore left Antigonus to conduct the siege of Thebes, and himself set out against this new foe. Pyrrhus, however, made a swift retreat, whereupon Demetrius stationed ten thousand men-at-arms and a thousand horsemen in Thessaly and once more devoted himself to Thebes.
Edition :
Plutarch. Plutarch's Lives. with an English Translation by. Bernadotte Perrin. Cambridge, MA. Harvard University Press. London. William Heinemann Ltd. 1920. 9.