κατὰ μέσον τὸ τῶν πολεμίων: the preposition is needed. “He yelled to Clearchus to lead the army to the enemy’s center.” μέσος is used adjectivally as often. A little earlier we had κατὰ γὰρ μέσον τὸν σταθμὸν τοῦτον τάφρος ἦν (7.14), “In the middle of this stage was a ditch.”
So in 1.8.12 in κατὰ μέσον τὸ τῶν πολεμίων is it the adjective μέσος, η, ον that we have here? I thought it might be the neuter noun μέσον, ου in this instance…and how can one tell which is used here?