Maybe there were some differences between the army of Yehoshua bin Nun and, להבדיל אלף אלפי הבדלות, the IDF?
1. No girls.
2. No chilonim.
3. No singles. (The draft age was 20, being single after 20 subjects one to condition number 4…)
4. No עברה of any kind, דאורייתא, or דרבנן, or עובר על דברי חכמים, up to and including interrupting between תפילין של יד and של ראש…
5. No Kohanim and Leviim.
6. Probably no one currently in the IDF, or in the Yeshivos for that matter, would make the grade.
ואם תמצא לומר, so how do we make an army now? Well, that’s a very good question. But it has absolutely nothing to do with the concept of a “Jewish Army” as described in Tanach and הלכות מלחמה of the Rambam. Nothing. Zero.