To the north the territory of Ammon was bounded by the plateau of Bashan and the Aramaic kingdoms of Gilead. Southward it extended towards the frontier of Moab, if indeed the borders of the two nations did not at one time coincide. When the Israelitish invasion, however, took place, the Amorites under Sihon had thrust themselves between, and had carved for themselves a kingdom out of the northern half of Moab. The land north of the Arnon became Amorite; but the Ammonite frontier was too well defended to be broken through.
The kingdom of Ammon maintained itself down to the time of David. At one time, in the days of the Judges, the Ammonites had made the Israelitish tribes on the eastern side of the Jordan tributary to them, and had even crossed the river and raided the highlands of Ephraim. Under Saul, Ammon and Israel were at constant feud. Saul had begun his reign by rescuing Jabesh in Gilead from the Ammonite king Nahash, who had threatened to treat its inhabitants with innate Semitic barbarity. When civil war broke out in Israel, Nahash naturally befriended David, and the alliance continued after David’s accession to the throne. Common interests brought them together. Esh-Baal, the successor of Saul in Gilead, was the enemy of both: his frontier adjoined that of Ammon, while between him and the King of Judah there was perpetual war. David had strengthened himself by marrying the daughter of the king of the Aramaic district of Geshur, which bounded Gilead on the north, and Ammonites and Aramaeans were in close alliance with each other.
As long as Nahash lived, there was peace between him and David. But with the accession of his son Hanun came a change. The King of Judah had become King of Israel, and his general, Joab, had subdued the neighbouring kingdom of Moab, and was looking out for a fresh field of fame. Hanun determined to forestall the war which he believed to be inevitable, and, in alliance with the Aramaeans, to crush the rising power of David. Family quarrels also probably conspired to bring about this resolution. In the after days of Absalom’s rebellion we find David entertained in Gilead by Shobi the brother of Hanun; it may be, therefore, that Hanun had had a rival in his brother, who had received shelter and protection at David’s court. At all events the Israelitish ambassadors were grossly insulted, and a long war with Ammon began. Campaign followed upon campaign; the City of Waters, Rabbah, the “capital” of Ammon, was closely invested, and the Aramaic allies of Hanun were put to flight. Rabbah fell at last; its defenders were tortured and slain, and the kingdom of Ammon annexed to the Israelitish empire.
When it recovered its independence we do not know. In the days of Assyrian conquest in the West it was already again governed by its own kings. One of them, Baasha, the son of Rehob, was, like Ahab of Samaria, an ally of Damascus against the Assyrian invader, and we hear of two others, one of whom bears the same name as “Shinab, King of Admah.” The storm of Babylonian conquest which overwhelmed Judah spared Ammon; after the destruction of Jerusalem Baalis was still king of the Ammonites, and ready to extend his power over the desolated fields of Judah.