Moroni is repeating his father’s perception that “none save it be the Lamanites and robbers” thrive (Morm. 2:8). He also apparently adopted wholesale the role in the Nephite destruction that Mormon assigned to the Gadianton robbers. As I have argued, these particular “Gadiantons” were actually military forces from Teotihuacan. (See Helaman, Part 1: Context, Chapter 3, “The Gadianton Robbers in Mormon’s Theological History: Their Structural Role and Plausible identification.”) Even though Mormon does not emphasize the Gadiantons specifically during the final round of battles their symbolic presence looms over the battlefield. They are certainly physically present in Teotihuacan’s influence on military tactics and goals. Now that the destruction has happened, the dominant force is these new-style Lamanites among whom are the “robbers” or Teotihuacanos.
The “Teotihuacanification” of Tikal [in the Maya lowlands of the Petén, Guatemala] had been going on since A.D. 250–350, but intensified just as the Book of Mormon is ending. Archaeologist Simon Martin and anthropologist Nikolai Grube describe this process:
Tikal enjoyed enduring contacts with Mexico and the great metropolis of Teotihuacan, 630 miles (1,013 km) to the west. Trade items such as green-hued obsidian were being imported from there as early as the 3rd century A.D., and local versions of the stepped masonry façade known as talud-tablero, a distinctly Mexican design, emerged at Tikal at about the same time. But towards the end of the 4th century there was an unprecedented surge in these foreign styles and artifacts, with distinctive ceramics—lidded tripods coated in stucco and painted with a range of Teotihuacan motifs—together with overt Mexican costume and symbolism on a group of monuments dated to this period. Tatiana Proskouriakoff dubbed the episode an “arrival of strangers” and even countenanced the invasion of a “foreign army.” These developments were certainly part of a much wider phenomenon across Mesoamerica at this time—equally evident at the Zapotec capital of Monte Albán [in the Valley of Oaxaca] and the highland Maya city of Kaminaljuyú [site of modern Guatemala City]—part of what Clemency Coggins has called the “Age of Teotihuacan” and a “New Order.”
Using a dated monument, Martin and Grube identify this “arrival” as occurring January 31, 378.