Passage 4.25.5
παρίστατο δέ σφισι πρὸ τῆς μελλούσης πολιορκίας ἀγῶνα ἐκ τοῦ φανεροῦ ποιήσασθαι, μηδὲ ὄντας Μεσσηνίους, οἳ μηδὲ Λακεδαιμονίων ἀνδρίᾳ, τύχῃ δὲ ἠλαττώθησαν, καταπεπλῆχθαι τὸν ἥκοντα ὄχλον ἐξ Ἀκαρνανίας· τό τε Ἀθηναίων ἐν Μαραθῶνι ἔργον ἀνεμιμνήσκοντο, ὡς μυριάδες τριάκοντα ἐφθάρησαν τῶν Μήδων ὑπὸ ἀνδρῶν οὐδὲ ἐς μυρίους ἀριθμόν.
Before the impending siege, they determined openly to engage in battle, lest the Acarnanian host that had come should lose heart, thinking that the Messenians, though defeated by the Spartans through adverse fortune rather than through inferiority in valor, were incapable fighters. They recalled too the deed of the Athenians at Marathon, in which thirty thousand of the Medes were destroyed by men numbering fewer than ten thousand.