They shall make captains Or rather, as the Hebrew is, they shall set or place the captains of the armies in the head or front of the people under their charge, that they may conduct them, and, by their example, encourage their soldiers. It is not likely they had their captain to make when they were just going to battle.
Related Commentaries of Deuteronomy 20:9
Deuteronomy 20:9
9 And it shall be, when the officers have made an end of speaking unto the people, that they shall make captains of the armies to leadd the people.