The rest of his men he put in the charge of Abishai his brother, and he arrayed them against the Ammonites.
Here we have, I. The preparation which the Ammonites made for war, Sa2 10:6. They saw they had made themselves very odious to David and obnoxious to his just displeasure. This they might easily have foreseen when they abused his ambassadors, which was no other than a challenge to war, and a bold defiance of him.
Commenting on 2 Samuel 10:6-14
And the rest of the people he delivered into the hands of Abishai his brother,.... Who was a commander under him, and a very valiant man; and thus, as his enemy had two armies, he divided his into two parts, that he might the better attack them: that he might put them in array against the children of Ammon: draw them up in a line...
2Sa 10:9-11 When Joab saw that “the front of the war was (directed) against him both before and behind,” he selected a picked body out of the Israelitish army, and posted them (the picked men) against the children of Aram (i.e., the Syrians). The rest of the men he gave to his brother Abishai, and stationed them against the Ammonites.
Commenting on 2 Samuel 10:9-11