ὁ μὲν χρῄζων λαμβανέτω ταῦτα καὶ ἀπογραφέσθω πρὸς τὸν ταξίαρχον εἰς τὴν ὁμοίαν τάξιν ἡμῖν
Here, the imperatives are used in the present tense, why not in the aorist, which would be more natural here?
By the way, in Russian imperfect imperatives can be used here just like in Greek (пусть берут оружие и записываются у таксиарха) but I don’t know how this changes the meaning even in Russian.
I could be wrong about this, but to me the present imperative feels less peremptory – an invitation rather than an order, as the context here suggests. Cyropaedia 2.1.18.
That’s true in Russian of the difference between imperfective and perfective imperatives: садитесь, “please have a seat” (host to guest) vs. сядьте, “sit down” (doctor to patient), though in general the imperfective/perfective opposition in Russian is quite different from the present/aorist opposition in Greek.
Again, it woud be helpful to add a cite when asking a question.