Alma 50

As I have recently watched several documentaries on U.S. expansion, it became clear that it was necessary to protect a young America against its adversaries including Great Britain, France, Mexico, Native Americans and so forth.  This morning I read that Moroni -

"...it came to pass that Moroni caused that his armies should go forth into the east wilderness; yea, and they went forth and drove all the Lamanites who were in the east wilderness into their own lands, which were south of the land of Zarahemla.
8 And the land of Nephi did run in a straight course from the east sea to the west.
9 And it came to pass that when Moroni had driven all the Lamanites out of the east wilderness, which was north of the lands of their own possessions, he caused that the inhabitants who were in the land of Zarahemla and in the land round about should go forth into the east wilderness, even to the borders by the seashore, and possess the land."  (Alma 50:7–9)

Since the beginning of time, land claim and war determined ownership.  In this case it was necessary for safety and protection.