Who was Hanun?
Hanun was a son and successor of Nahash, king of Ammon.
Upon the death of Nahash, David sent sympathetic communications to Hanun, which were misinterpreted and the messengers dishonored. Because of this indignity, David waged a war against him, which caused the Ammonites to lose their independence (2 Samuel 10:1 ; 1 Chronicles 19:1 ).
IBSE, "Isaac" (in the public domain) with minor edits.