2 Samuel 10:6-10

Now when the sons of Ammon saw that they had become repulsive to David, the sons of Ammon sent messengers and hired the Arameans of Beth-rehob and the Arameans of Zobah, twenty thousand foot soldiers, and the king of Maacah with a thousand men, and the men of Tob with twelve thousand men.

When David heard about this, he sent Joab and all the army, the warriors.

And the sons of Ammon came out and lined up for battle at the entrance of the city, while the Arameans of Zobah and of Rehob and the men of Tob and Maacah were stationed by themselves in the field.

Now when Joab saw that the battle was set against him at the front and at the rear, he selected warriors from all the choice men in Israel, and lined them up against the Arameans.

But the remainder of the people he placed under the command of his brother Abishai, and he lined them up against the sons of Ammon.