He put the rest of the men under the command of Abishai his brother and deployed them against the Ammonites.
References for 2 Samuel 10:10
Joab said, “If the Arameans are too strong for me, then you are to come to my rescue; but if the Ammonites are too strong for you, then I will come to rescue you.
Be strong, and let us fight bravely for our people and the cities of our God. The LORD will do what is good in his sight.”
References for 2 Samuel 10:12
Then Joab and the troops with him advanced to fight the Arameans, and they fled before him.
When the Ammonites realized that the Arameans were fleeing, they fled before Abishai and went inside the city. So Joab returned from fighting the Ammonites and came to Jerusalem.
References for 2 Samuel 10:14