Alma 50:11 - 50:15
Alma 50: 11 And thus he cut off all the strongholds of the Lamanites in the east wilderness, yea, and also on the west, fortifying the line between the Nephites and the Lamanites, between the land of Zarahemla and the land of Nephi, from the west sea, running by the head of the river Sidon—the Nephites possessing all the land northward, yea, even all the land which was northward of the land Bountiful, according to their pleasure.
By removing the Lamanites from the east wilderness and in addition on the west, Moroni created a fortified line between the Nephites in the land of Zarahemla and the Lamanites in the land of Nephi. This line ran from the west sea to the head waters of the Sidon river. The Nephites now controlled all the land northward even the areas north of the land Bountiful.
Alma 50: 12 Thus Moroni, with his armies, which did increase daily because of the assurance of protection which his works did bring forth unto them, did seek to cut off the strength and the power of the Lamanites from off the lands of their possessions, that they should have no power upon the lands of their possession.
As a result of Moroni’s administration, the Nephites were able to create a defensive posture that would give them confidence that they could withstand the coming of the Lamanites, which all knew was on a manner of time.
>Alma 50: 13 And it came to pass that the Nephites began the foundation of a city, and they called the name of the city Moroni; and it was by the east sea; and it was on the south by the line of the possessions of the Lamanites.
Along with fortifying existing cities, new ones were created in places to enhance the defenses of the Nephites. One was named Moroni and was located by the east sea just south of the line that separated the Nephite lands from the Lamanites.
Alma 50: 14 And they also began a foundation for a city between the city of Moroni and the city of Aaron, joining the borders of Aaron and Moroni; and they called the name of the city, or the land, Nephihah.
Another city was created called Nephihah. It lay between the new city of Moroni and the city of Aaron.
Alma 50: 15 And they also began in that same year to build many cities on the north, one in a particular manner which they called Lehi, which was in the north by the borders of the seashore.
Cities were also created on the north of the Nephites lands. One city was called Lehi and near the sea shore.