1 Chronicles 19:18-19

New International Version

¹⁸ But they fled before Israel, and David killed seven thousand of their charioteers and forty thousand of their foot soldiers. He also killed Shophak the commander of their army.

¹⁹ When the vassals of Hadadezer saw that they had been routed by Israel, they made peace with David and became subject to him.

So the Arameans were not willing to help the Ammonites anymore.