Passage 7.15.7
Ἀχαιοῖς δὲ αὖθις ἐπὶ τὴν ἡγεμονίαν τοῦ στρατεύματος παρῄει Δίαιος· καὶ δούλους τε ἐς ἐλευθερίαν ἠφίει, τὸ Μιλτιάδου καὶ Ἀθηναίων βούλευμα τὸ πρὸ τοῦ ἔργου τοῦ ἐν Μαραθῶνι μιμούμενος, καὶ Ἀχαιῶν συνέλεγε καὶ Ἀρκάδων ἀπὸ τῶν πόλεων τοὺς ἐν ἡλικίᾳ· ἐγένετο δέ, ἀναμεμιγμένων ὁμοῦ καὶ οἰκετῶν, τὸ ἀθροισθὲν ἐς ἑξακοσίους μὲν μάλιστα ἀριθμὸν ἱππεῖς, τὸ δὲ ὁπλιτεῦον τετρακισχίλιοί τε καὶ μύριοι.
Once again the leadership of the army among the Achaeans devolved upon Diaeus. He granted freedom to slaves, imitating the policy adopted previously by Miltiades and the Athenians before the battle of Marathon. Additionally, he gathered all the men in their prime from among the cities of the Achaeans and Arcadians. The assembled army, including the slaves now mingled within it, amounted approximately to six hundred cavalry and fourteen thousand infantrymen.