Mormon takes evident pleasure in describing the consternation of the Lamanites. While the import of these passages is to show that the Lamanite incursion did not succeed because of Moroni’s fortifications, there are other tidbits of information that we can learn from these verses.
The first is that the Lamanites are clearly not stupid. They had been beaten back in the attack on Jershon because of the Nephite innovation of armor. They took note of that innovation, and clearly replicated that innovation. In verse 6 we now see the Lamanites with a different set of military dress. Just as the Nephites, they are now “prepared… with shields, and with breastplates; and they had also prepared themselves with garments of skins, yea, very thick garments to cover their nakedness.” The Lamanites who had surrendered to Moroni might have kept their promise not to fight, but there was no promise that they wouldn’t divulge the Nephite “secret” of body armor. This rapid diffusion of a military technological advance was very typical in the limited technology available in Mesoamerica (Ross Hassig. Aztec Warfare. University of Oklahoma Press, 1988, p. 92).
The second thing we learn is that fortifications were also an innovation. It is perhaps another reason that Mormon so admired Moroni, because Moroni was not simply a leader of men, he appears to have been a brilliant innovator, one whose innovations appear to have altered the course of military history in Mesoamerican thereafter, as the items which appear as innovations with Moroni become normal for later armies and cities.