Deuteronomy 20:9

they shall appoint They, not necessarily the officersof the previous clause, but indefinite: those whose duty it is to appoint, or the people as a whole. Cp. 1Ma 3:55 f.

captains of hosts The chiefs of the main divisions, cp. 1 Kings 2:5. These are not appointed till the host has been sifted of all whom it was not proper to allow to accompany it, because the exemptions apply to all ranks. With these rules for sifting the host, cp. Cromwell's measures with the recruits for his Ironsides.