The subject of a finite verb is in the nominative: Κῦρος ἐβόᾱ Cyrus called out.
THE SUBJECT
§§927–928 · 2 sections
The subject nominative may be replaced
a. By a prepositional phrase in the accusative: ἐνθῡμεῖσθε καθ᾽ ἑκάστους τε καὶ ξύμπαντες
consider individually and all together 7.64.
b. By a genitive of the divided whole (1318): Πελληνεῖς δὲ κατὰ Θεσπιέᾱς γενόμενοι ἐμάχοντό τε καὶ ἐν χώρᾳ ἔπῑπτον ἑκατέρων
the Pellenians who were opposed to the Thespians kept up the contest and several on both sides fell on the spot H. 4.2.20.