The promise of protection is not free. The people of Zarahemla extract a tribute from the Anti-Nephi-Lehies. A portion of their substance will be given to Zarahemla for the maintenance of the army that will provide protection. Jershon is being set up as a dependant state on the greater policy of Zarahemla.
“We Will Give Up the Land of Jershon”
The stated reason for allowing the Anti-Nephi-Lehies a specific land of their own is that they may be protected. It may have been the unstated purpose that should these repentant Lamanites ever decide to choose their old ways, the people of Zarahemla might also be protected by the same forces providing the protective buffer for the Anti-Nephi-Lehies.
The proclamation somehow communicated the essentials of the Anti-Nephi-Lehite conversion, for the declaration includes the information that the Anti-Nephi-Lehies choose not to arm themselves. This clearly leads to the offer of protection, but may have also played some part in the willingness to accept converted Lamanites among the Nephites. Given the history of tensions between these two peoples, it must have been comforting that these Lamanites that were coming into their land were unarmed. That they were now believers was good, that they were unarmed may have been even better.
Geographic: In Sorenson’s geography, the land of Jershon lies deep in Nephite territory close to the coast on the far side of the narrow neck. As he traces the path of these immigrants, he notes: “The Anti-Nephi-Lehis, or people of Ammon, as they now came to be called, were given a land of their own, Jershon. Informed of that, they moved through Gideon (Comitan Valley), along the upland route, and down to their new home near the east sea without ever seeing Zarahemla itself. (John L. Sorenson, An Ancient American Setting for the Book of Mormon [Salt Lake City and Provo: Deseret Book Co., Foundation for Ancient Research and Mormon Studies, 1985], 231.)
When the converted Lamanites—the Anti-Nephi-Lehis—arrived in the land of Zarahemla, they were sent to the land of Jershon as part of a plan by the government to guard against a possible Lamanite invasion. Jershon was in a region of crucial weakness in the Nephite defenses; the east lowlands needed garrisoning, and the Anti-Nephi-Lehis would serve the purpose. While these former Lamanites had become pacifists, they could at least provide logistical support for the Nephite armies in the zone. (John L. Sorenson, An Ancient American Setting for the Book of Mormon [Salt Lake City and Provo: Deseret Book Co., Foundation for Ancient Research and Mormon Studies, 1985], 239.)