Bountiful was a stronghold deep in the northern section of the land of Zarahemla. Moroni is treating it as a safe location for prisoners. Once the Lamanites are distant from the land of Nephi and well guarded, he hopes they will become resigned to their status and not attempt to escape or to attack their guards, though it is likely that he has also extracted an oath from them as he had done before. (See commentary accompanying Alma 44:5–20.)