Unfortunately for the Limhites, it is also not surprising that the Lamanites should have beaten them back. We were told in the beginning of the story of the destruction of Noah that the army was greatly reduced (Mosiah 19:2). In addition, Alma had taken a number of people away, certainly including some able bodied men. Finally, while the ambush had been successful, there were no doubt Limhite casualties. The ambush worked precisely because it was an ambush, as they were already outnumbered about two to one (Mosiah 20:11). With the Lamanites surrounding the Limhites, and with clear numerical superiority, and with an expectation of violence (and perhaps even the hope of provoking it) the Limhites went forth to a doomed battle.
It is culturally important, however, to note that when the Limhites are defeated and driven back, there is no further attack upon the city. The tribute function was still important, and the effect of the force of arms was to pacify the population and return them to profitable tributaries. The war of retaliatory destruction that one might expect from the history of western warfare did not happen.
Geography: The Lamanites are able to surround the Limhites, and it appears that all Limhite action comes from a single location. We may suppose that this is the city of Lehi-Nephi. Early in the story of Zeniff, we heard that Zeniff was also granted the land of Shilom (Mosiah 9:6) and that Noah had a building project in Shilom (Mosiah 10: 13). Nevertheless, at this point we have no indication of any Limhites in Shilom. Somewhere in the untold history of this people, Shilom was lost. Perhaps it was lost in the time of Noah, and may have been a struggle that resulted in the diminution of the king's army (as noted in Mosiah 19:2).
In any case, Shilom is lost, and Limhi and his people are surrounded in Lehi-Nephi. It is to that one remaining city that Ammon will come.