And he put garrisons in Edom
To keep the inhabitants in subjection to him; as their forts and strong holds came into his hands, he placed companies of soldiers in them for the said purpose; or governors, as the Targum, men of his own nation, into whose hands he put their principal cities, who governed them for him, and under him. Jarchi interprets it of officers appointed to collect the tribute he exacted of them:
throughout all Edom put he garrisons;
which is observed to show that the whole country was brought into subjection to him:
and the Lord preserved David whithersoever he
(See Gill on 2 Samuel 8:6).