When the Achaeans came to Argos again for the conference, and Cleomenes had come down from Tegea, everyone had a strong hope that they would come to an agreement. But Aratus, since the most important questions between him and Antigonus had already been settled, and because he was afraid that Cleomenes would carry all his points by either winning over or constraining the multitude, demanded that Cleomenes, after receiving three hundred hostages, should come into the city alone for his conference with them, or else should come with his army as far as the gymnasium outside the city called Cyllarabium, and treat with them there.
When Cleomenes heard this, he declared that he had been wronged; for he ought to have been told of this when the conference was first proposed, and not be distrusted and driven away now, when he had come to their very doors. Then, after writing a letter to the Achaeans on the matter, most of which was denunciation of Aratus, and after Aratus on his part had abused him at great length to the multitude, Cleomenes broke camp with all speed and sent a herald to declare war upon the Achaeans, not to Argos, but to Aegium, in order, as Aratus says, that he might anticipate their preparations for defence.1
Now, there had been agitation among the Achaeans, and their cities were eager for revolt, the common people expecting division of land and abolition of debts, and the leading men in many cases being dissatisfied with Aratus, and some of them also enraged at him for bringing Macedonians into Peloponnesus. Therefore Cleomenes, encouraged by these conditions, invaded Achaea. First, he took Pellené by a sudden assault, and drove out the Achaean garrison; next, he brought over to his cause Pheneus and Pentelcium.
Presently the Achaeans, who were afraid that some treachery was afoot in Corinth and Sicyon, sent their horsemen and their mercenaries out of Argos to keep watch over those cities, while they themselves went down to Argos and began celebrating the Nemean games. So Cleomenes, expecting, as was the case, that while the throng was holding festival and the city was full of spectators, his unexpected approach would be more apt to cause confusion, led his army by night up to the walls,
occupied the region about the Aspis overlooking the theatre, a region which was rugged and hard to come at, and so terrified the inhabitants that not a man of them thought of defence, but they accepted a garrison and gave twenty citizens as hostages, agreeing to become allies of the Lacedaemonians, and to give Cleomenes the chief command.