We find in Mormon 1:10 that "the war began to be among them in the borders of Zarahemla, by the waters of Sidon." If the term Zarahemla means the general land of Zarahemla, then these borders might somewhat match the borders described in Alma 22:27. In that verse a description is given of a narrow strip of wilderness which divided the land on the north (Zarahemla) from the land on the south (Nephi). This narrow strip of wilderness went "through the borders of Manti, by the head of the river Sidon, running from the east towards the west". This border location seems logical because of the Nephite history in which that area was fortified -- the city of Manti being established there. This area is mentioned heavily in regards to travel and battles between the people of Nephi and Zarahemla. Any other location, although possible, would need some explanation. It is an interesting cultural note that although the Lamanites and Nephites at one time "were one" (4 Nephi 1:17) and were spread out "upon all the face of the land" (4 Nephi 1:2), the war between the Lamanites and Nephites began here, of all places, in these historically and militarily significant "borders of Zarahemla by the waters of Sidon." [Alan C. Miner, Personal Notes] [See Geographical Theory Maps]
“The Waters of Sidon”
John Sorenson notes that the conflict that was to result in extermination of the Nephite lineages began in the same place as the earlier wars--where expanding Lamanite power on the south rubbed against the Nephite political presence. "The war began to be among them in the borders of Zarahemla, by the waters of Sidon" (Mormon 1:10).
As has been noted before (see Alma 31:3; Alma 50:8), southeast Chiapas formed a boundary between speakers of Maya languages and other groups, particularly the Zoqueans, who had been among the bearers of the Olmec/Jaredite tradition. Our glimpses of ethnic history before the time of Columbus indicate that the Maya speakers occupied nearly all the lands we have identified as included in the greater land of Nephi. The mass of folk governed by the Lamanite lineage of rulers probably spoke one or another Mayan tongue. The tendency of the speakers of those languages, as shown by linguistic reconstruction, has been to expand in a northern and western direction into Chiapas. It seems almost historically inevitable that the Mayan/Lamanite movement would crowd the southern edge of the Nephite domain. The renewed conflict in the fourth century at that particular geographical point adjacent to the Sidon and to Zarahemla fits in as a logical continuation of the process begun centuries before. [John L. Sorenson An Ancient American Setting for the Book of Mormon, pp. 335-336]
Geographical [Theory Map]: Mormon 1:10 War Starts in the Borders of Zarahemla (322 A.S.--326 A.S.)