Alma 50:10

And he also placed armies on the south, in the borders of their possessions, and caused them to erect fortifications, that they might secure their armies and their people from the hands of their enemies.

He also put armies in the south on the borders. He told them to build forts so they could keep their armies and people safe from their enemies.

He also stationed armies on the southern border and had them build fortifications to protect his armies and people from enemy attack.