in sober earnest

From LSJ

μοῦνοι Ἑλλήνων δὴ μουνομαχήσαντες τῷ Πέρσῃ → alone of all Greeks we met the Persian singlehandedly, alone of all Greeks having fought singlehanded with the Persians

Source

English > Greek (Woodhouse Extra)

ἀληθῶς