The new king, Amalickiah’s brother (see verse 3), was able to leave the land of Zarahemla to report Amalickiah’s death. In Mesoamerica, it was not infrequent that rulership would pass to a brother rather than directly to a son, and thus we see Ammoron becoming the new king. That fact is not mentioned here, but is specifically noted in Alma 54:16. Among the Nephites, we see this happening more often among the recordkeepers. Not only does Nephi give the records to his brother, Jacob, but we see it again when Amaron gives the records to his brother Chemish in Omni 1:8.
The attack on the west is an intentional tactic to divide the Nephite military strength. The Book of Mormon consistently indicates that there are more Lamanites than Nephites, so dividing the Nephite armies would have had a greater impact on the Nephites than this division of Lamanite armies had upon the Lamanites.
Mormon sets the tension of the times by noting that it was “in those dangerous circumstances” that the twenty-sixth year ended.