This brief section appears to have been inserted by Mormon to show how the wicked will not support each other, will turn against each other to everyone’s harm, and how the Lord’s prophecies will be fulfilled.
Some of those who had been violently opposed to the Anti-Nephi-Lehies were pure literal Lamanites, “actual descendants of Laman and Lemuel” (24:29), and they became very upset that their supposed allies had used them to kill so many of their own Lamanite brethren (24:28). Most of the leaders who had led the attacks on the Anti-Nephi-Lehies were, in fact, “after the order of Nehors” (24:28), who were Nephites, or were “the seed of Amulon,” who were priests of Noah, also a Nephite (25:4). The Lamanites, now becoming angry because those people had “slain their [Lamanite] brethren” (25:1), turned their vengeance “upon the Nephites” (25:1). In particular, they chose as their target “the land of Ammonihah,” not only because it was close (being near the head of the River Sidon, including the cities of Melek, Sidom and Ammonihah), but also because Ammonihah was the headquarters of the Order of Nehors. These Lamanites “fell upon the people in the land of Ammonihah and destroyed them” (25:1), leaving it as the “Desolation of Nehors” reported back in Alma 16:9–11. This explains the not so obvious reasons why the Lamanites attacked the borders of the land of Zarahemla and destroyed the city of Ammonihah (25:1–2).
While few details are given, among those who attacked this Nephite territory were both Lamanites, many of whom were driven and slain (25:3), and also “almost all the seed of Amulon,” and they were slain by the Nephties (25:4). The remainder of this Lamanite force, including “the remnant of the children of Amulon,” then fled into the east wilderness (not wanting to return to the land of Nephi). Those Amulonites then usurped “power and authority over the Lamanites” (25:5) and put to death any Lamanites who began to disbelieve the traditions of the Lamanites and wanted defect over to the side of the Nephites. But those additional martyrdoms caused “contention in the wilderness” (25:8), and those last remaining Amulonites were then hunted and killed, thus fulfilling the prophecies of Abinadi (25:7–12).