Alma 22:31 - 22:35
Alma 22:31 And they came from there up into the south wilderness. Thus the land on the northward was called Desolation, and the land on the southward was called Bountiful, it being the wilderness which is filled with all manner of wild animals of every kind, a part of which had come from the land northward for food.
The Lamanite, who live in these wilderness areas on the north had come up from the wilderness areas in the south. As a result the land to the north of the wilderness was called Desolation, named that because it was where the discovery of an unknown destroyed civilization had been made. The land to the south which was part wilderness was called Bountiful on account of it being filled with many wild animals which had immigrated down from the north.
Alma 22:32 And now, it was only the distance of a day and a half’s journey for a Nephite, on the line Bountiful and the land Desolation, from the east to the west sea; and thus the land of Nephi and the land of Zarahemla were nearly surrounded by water, there being a small neck of land between the land northward and the land southward.
The narrow neck of land that separated the land of Nephi and the land of Zarahemla could be cross in a day and a half by a Nephite.
Alma 22:33 And it came to pass that the Nephites had inhabited the land Bountiful, even from the east unto the west sea, and thus the Nephites in their wisdom, with their guards and their armies, had hemmed in the Lamanites on the south, that thereby they should have no more possession on the north, that they might not overrun the land northward.
In order to keep the Lamanites in an area they could have complete control over, they settled all the lands in the land Bountiful and had stationed armies and guards between these two lands to keep the Lamanites to the south.
Alma 22:34 Therefore the Lamanites could have no more possessions only in the land of Nephi, and the wilderness round about. Now this was wisdom in the Nephites—as the Lamanites were an enemy to them, they would not suffer their afflictions on every hand, and also that they might have a country whither they might flee, according to their desires.
By keeping the Lamanites to the south, the Nephites could then flee to the north and not have to fight their way north out of the land Bountiful, if they could not defeat any invading Lamanite army.
Alma 22:35 And now I, after having said this, return again to the account of Ammon and Aaron, Omner and Himni, and their brethren.
Now that Mormon has set the stage showing the lay of the land, he will return to the story of the ministry of the sons of Mosiah and their companions.