Plutarch, Cleomenes
Bernadotte Perrin, Ed.

21. It was about midnight when Cleomenes heard of these things, and summoning Megistonoüs, he angrily ordered him to go at once to Argos with assistance; for it was Megistonoüs who had given him most assurances of the fidelity of the Argives, and had thereby prevented him from expelling the suspected citizens. After sending off Megistonoüs, then, with two thousand soldiers, he himself kept watch upon Antigonus and tried to encourage the Corinthians, telling them that there was no great trouble at Argos, but only a slight disturbance made by a few men. [2] However, when Megistonoüs, who had made his way into Argos, was slain in battle, and the garrison held out with difficulty and kept sending frequent messengers to Cleomenes, he was afraid that if the enemy made themselves masters of Argos and shut up the passes, they might ravage at will the Laconian territory and lay siege to Sparta, which he had left without defenders. He therefore led his army away from Corinth. [3] This city was at once lost to him, for Antigonus entered it and set a garrison there; but Cleomenes, on reaching Argos, made an attempt to scale the walls, and with this in view drive his forces together from their march, and cutting his way through the tunnels running under the Aspis, or citadel, he made the ascent and effected a junction with his garrison inside, which was still holding out against the Achaeans. He actually got possession of some portions of the city by using scaling-ladders, and cleared the streets of the enemy by bringing his Cretan archers into action. [4] But when he saw Antigonus with his phalanx descending from the heights into the plain, and his horsemen already streaming into the city, he gave up trying to master it; and gathering all his troops about him he made his way safely down from the citadel and withdrew along past the city wall. He had made the greatest possible conquests in the briefest possible time, and had come within a little of making himself master of all Peloponnesus by a single march through it, but had quickly lost everything again. For sonic of his allies left him at once, and others after a little while handed their cities over to Antigonus.