The Ammonites were regarded as relatives of the Israelites, who were commanded to treat them kindly (Deuteronomy 2:19). At an early date the Ammonites occupied the territory between the Arnon and Jabbok rivers (Deuteronomy 2;20-21, 37). At the time of the Exodus, Israel did not conquer Ammon (Deuteronomy 2:19, 37; Judges 11:15). However, the Ammonites were condemned for joining the Moabites in hiring Balaam, and were forbidden to enter the congregation of Israel to the 10th generation (Deuteronomy 23:3-6). Their chief town was Rabbath (Rabbah), modern Amman.
In the days of the Judges, the Ammonites assisted Eglon of Moab to subdue Israelite territory (Judges 3:13). In the time of David the Ammonites went to war against Israel. The Israelites captured Rabbah, the Ammonite capital (2 Samuel 12:26-31; 1 Chronicles 20:1-3) and put the people to work. Later, Solomon included Ammonite women in his harem, and worshipped Milcom (Molech) their god (1 Kings 11:1,5,7,33). An Ammonitess, Naamah, was the mother of Rehoboam (1 Kings 14:21,31; 2 Chronicles 12:13). In the days of Jehoshaphat, the Ammonites joined Moabites and Edomites in a raid on Judah (2 Chronicles 20:1-30).
The Ammonites were bitterly attacked by the prophets as inveterate enemies of Israel (Jeremiah 49:1-6; Ezekiel 21:20; 25:1-7). [Tyndale House, The Illustrated Bible Dictionary , Vol. 1, pp. 40-42]
2 Nephi 21:14 Ammon ([Illustration]): The territory of the Ammonites, to the east of the river Jabbok. [Tyndale House, The Illustrated Bible Dictionary , Vol. 1, p. 41]