Alma 48:8

yea, he had been strengthening the armies of the Nephites, and erecting small forts, or places of resort; throwing up banks of earth round about, to enclose his armies, and also building walls of stone to encircle them about, round about their cities, and the borders of their lands; yea, all round about the land;

He had been making the Nephite armies stronger. He built small forts where they could go for safety. He threw up piles of dirt around the armies. He also built stone walls around them. He did this around their cities and along the borders of their lands. He did this all around the land.

He’d been building up the Nephite armies and constructing small forts and defensive positions. He threw up earthen walls around his forces and built stone barriers to circle their cities and protect their borders—all around the land.