Βουλόμεθα νῦν σκέπτεσθαι, ποῖον δεῖ τὸν φύλακα εἶναι καὶ τί ὲστι τὸ τῶν φυλάκων ἔργον. Πρὸς μὲν τοὺς οἰκείους πράους δεῖ τοὺς φύλακας εἶναι, πρὸς δὲ τοὺς πολεμίους χαλεπούς.
I think that here τοὺς φύλακας εἶναι belongs to the subject part, and the real predicate “ἐστί” is omitted. In other words, I think the sentence should be “It’s necessary that guards are very friendly to friends/people of our own but difficult/cruel to enemies.”
Am I right?