οἴεσθαι δὲ δεῖ καὶ ἄλλα πολλά τε καὶ παντοδαπὰ ποιεῖν αὐτούς, πλὴν ἐμάχετο οὐδείς, ἀλλ᾽ ἀμαχητὶ ἀπώλλυντο. would it be possible to use inf + acc after πλὴν: πλὴν μαχέσασθαι οὐδὲνα άλλ΄ απολέσθαι
though I think it would be better to add the article τοῦ before the infinitive.