2 Samuel 10:18-19

New International Version

¹⁸ But they fled before Israel, and David killed seven hundred of their charioteers and forty thousand of their foot soldiers.^[a] He also struck down Shobak the commander of their army, and he died there. ¹⁹ When all the kings who were vassals of Hadadezer saw that they had been routed by Israel, they made peace with the Israelites and became subject^(A) to them.

So the Arameans^(B) were afraid to help the Ammonites anymore.