2 Samuel 10:6-11

Now when the sons of Ammon saw that they had become odious to David, the sons of Ammon sent and hired the Arameans of Beth-rehob and the Arameans of Zobah, 20,000 foot soldiers, and the king of Maacah with 1,000 men, and the men of Tob with 12,000 men. When David heard of it, he sent Joab and all the army, the mighty men. The sons of Ammon came out and drew up in battle array at the entrance of the city, while the Arameans of Zobah and of Rehob and the men of Tob and Maacah were by themselves in the field. Now when Joab saw that the battle was set against him in front and in the rear, he selected from all the choice men of Israel, and arrayed them against the Arameans. But the remainder of the people he placed in the hand of Abishai his brother, and he arrayed them against the sons of Ammon. He said, “If the Arameans are too strong for me, then you shall help me, but if the sons of Ammon are too strong for you, then I will come to help you.