Alma 22: 29

29 And also there were many Lamanites on the east by the seashore, whither the Nephites had driven them. And thus the Nephites were nearly surrounded by the Lamanites; nevertheless the Nephites had taken possession of all the northern parts of the land bordering on the wilderness, at the head of the river Sidon, from the east to the west, round about on the wilderness side; on the north, even until they came to the land which they called Bountiful. Once more lots of detail about geography. Mormon could have simply said the Nephites were nearly surrounded by Lamanites on every side.  See video for details https://youtu.be/rHVh3bDYGRE