TT #308 · Parashas Shoftim · Seventh Aliyah · Passuk 20:09
And it shall be, when the officers have finished speaking to the people, that they shall appoint commanders of the armies at the head of the people.
Torah Temimah points to Sotah 44a / Sifrei.
TT lemma: וּפָקְדוּ שָׂרֵי צְבָאוֹת.
English: ‘They shall appoint commanders of the armies at the head of the people’ – above the people.
Derash on the organization of the army (Bavli / Sifrei) — the final step is the appointment of officers over the purified ranks.
Once the exempted men have been released, commanders are appointed over the army that remains.