When the Ammonites saw that the Arameans had fled, they too fled before Joab's brother Abishai, and they entered the city. So Joab went back to Jerusalem.

1 Chronicles 19:14
So Joab and his troops advanced to fight the Arameans, who fled before him.

1 Chronicles 19:16
When the Arameans saw that they had been defeated by Israel, they sent messengers to bring more Arameans from beyond the Euphrates, with Shophach the commander of Hadadezer's army leading them.

And when the children of Ammon saw that the Syrians were fled, they likewise fled before Abishai his brother, and entered into the city. Then Joab came to Jerusalem.