Passage 7.12.6
πόλεμός τε δὴ ἀπὸ τῶν ἀμφισβητημάτων τούτων Ἀχαιοῖς καὶ Λακεδαιμονίοις ἤρχετο καὶ Λακεδαιμόνιοι συνιέντες οὐκ ἀξιόμαχοι πρὸς Ἀχαιοὺς εἶναι πρεσβείαις ἐχρῶντο πρὸς τὰς πόλεις αὐτῶν καὶ ἰδίᾳ πρὸς τὸν Δίαιον λόγοις. αἱ μὲν δὴ κατὰ τὰ αὐτὰ αἱ πόλεις ἐποιοῦντο τὰς ἀποκρίσεις, οὔ σφισιν ἔξοδον ἐπαγγέλλοντος στρατηγοῦ παρακούειν εἶναι νόμον· Δίαιος γὰρ ἦρχε τῶν Ἀχαιῶν καὶ ἔφασκεν οὐ τῇ Σπάρτῃ, τοῖς δὲ ταράσσουσιν αὐτὴν πολεμήσων ἀφίξεσθαι.
Thus from these disputes war began between the Achaeans and the Lacedaemonians. Realizing they were not equal to the Achaeans in strength, the Lacedaemonians sent embassies both to their cities and privately to Diaeus himself. The cities made their replies uniformly, saying it was not lawful to disobey their general when he called for a campaign. At that time Diaeus held command of the Achaeans, and he declared that he was not marching against Sparta itself, but against those who were causing trouble within it.