According to Cleon Skousen, in the city of Bountiful first they built a very high breastwork of timbers along what was going to be the inner bank of the ditch. Then, as they dug the ditch the dirt was piled up against this breastwork so that they achieved a moat and high wall of earth at one stroke. The city of Bountiful was completely encircled by this means. This made Bountiful one of the major strongholds of the Nephites from then on. The unique feature of its fortifications was that it not only provided a virtually unassailable moat and wall against any outside attack, but the high breastworks made it equally difficult for a person to escape from the inside. This breastwork was not on the top of the earthen bank as Moroni had done earlier (Alma 50:2-3), but commenced from the ground upward and was "exceeding" high (Alma 53:4). Bountiful was therefore converted into a prison-city and the Lamanite captives were held there behind a wall which they had built with their own hands. [W. Cleon Skousen, Treasures from the Book of Mormon, Vol. 3, p. 3149]