Passage 4.29.7
ὃ δὲ οὐ λέληθεν ἐμέ, οὐδὲ Μεσσηνίους ἐλελήθει δήπου, καὶ μὴ συντελοῦσιν αὐτοῖς ἐς τὸ συνέδριον ὡς ἐπὶ Λακεδαιμονίους τὰ Ἀχαιῶν ὑπάρχοι· ἐν γὰρ δὴ τοῖς Ἀχαιοῖς καὶ Ἀργεῖοι καὶ τὸ Ἀρκαδικὸν οὐκ ἐλαχίστη μοῖρα ἦσαν. ἀνὰ χρόνον μέντοι προσεχώρησαν ἐς τὸ Ἀχαϊκόν. οὐ πολλῷ δὲ ὕστερον Κλεομένης ὁ Λεωνίδου τοῦ Κλεωνύμου Μεγάλην πόλιν εἷλεν Ἀρκάδων ἐν σπονδαῖς·
But this fact has not escaped my notice, nor could it, I suppose, have escaped the Messenians themselves, that by not contributing to the council, the direction of Achaean policy toward Sparta would lie outside their influence; for among the Achaeans, the Argives and the Arcadians formed no small portion. However, in due time they did join the Achaean League. Not long afterward, Cleomenes, son of Leonidas, grandson of Cleonymus, captured Megalopolis, a city of the Arcadians, during a period of truce.