Passage 8.8.11
τούτων δὲ ὕστερον διαφορὰ ἐγένετο Μαντινεῦσιν ἐς τοὺς Λακεδαιμονίους, καὶ ἀπʼ αὐτῶν μετέστησαν ἐς τὸ Ἀχαϊκόν· καὶ Ἆγιν τὸν Εὐδαμίδου βασιλεύοντα ἐν Σπάρτῃ νικῶσιν ἀμύνοντες τῇ σφετέρᾳ, νικῶσι δὲ προσλαβόντες Ἀχαιῶν στρατιὰν καὶ Ἄρατον ἡγεμόνα ἐπʼ αὐτῇ. μετέσχον δὲ καὶ πρὸς Κλεομένην τοῦ ἔργου τοῖς Ἀχαιοῖς καὶ συγκαθεῖλον Λακεδαιμονίων τὴν ἰσχύν. Ἀντιγόνου δὲ ἐν Μακεδονίᾳ Φίλιππον τὸν Περσέως πατέρα ἔτι παῖδα ἐπιτροπεύοντος καὶ Ἀχαιοῖς ἐς τὰ μάλιστα ὄντος ἐπιτηδείου, ἄλλα τε ἐς τιμὴν αὐτοῦ Μαντινεῦσιν ἐποιήθη καὶ ὄνομα τῇ πόλει μετέθεντο Ἀντιγόνειαν.
Afterward, the Mantineans came into dispute with the Lacedaemonians and deserted them, joining the Achaean League. While defending their territory, they defeated Agis, son of Eudamidas, then king at Sparta, prevailing with the aid of an Achaean army under the leadership of Aratus. They also took part with the Achaeans in the struggle against Cleomenes, and together they broke the power of the Lacedaemonians. At the time when Antigonus was guardian of Philip, the son of Perseus' father, in Macedonia, and particularly friendly toward the Achaeans, among other honors shown to Antigonus, the Mantineans renamed their city Antigoneia.