Mormon is able to rally his army to victories, and finally place the Lamanite/Gadiantons on the defensive. Mormon does not tell us how this happened, but does indicate that he does not thing that it was because of the Lord, for he says “nevertheless the strength of the Lord was not with us.” This suggests that there were less than miraculous reasons for the reversal of fortune. If we attempt to reconstruct what those conditions might have been, we begin with the defeat of the Lamanite/Gadianton army at Shem. At attacking army is usually at a disadvantage because it is relatively unprotected while it is assaulting a protected location.
Therefore, their defeat tells us that not only were they unsuccessful, but they had suffered heavy casualties. This diminished force is the one that is retreating and is being pursued by Mormon. It is also possible that in spite of the previous harvest, their supply lines had become over-extended. In any case, it is now the Lamanite/Gadianton army that retreats. Mormon says that the Nephites took “possession of the lands of our inheritance,” which might indicate that they had retaken Zarahemla. However, this is not stated, and the nature of the treaty suggests that they were not able to move that far south.