Textual: Compare the end of the previous chapter with the beginning of this chapter:
Hel. 10:18
18 And it came to pass that they would not hearken unto his words; and there began to be contentions, insomuch that they were divided against themselves and began to slay one another with the sword.
Hel. 10:19
19 And thus ended the seventy and first year of the reign of the judges over the people of Nephi.
At the end of the previous chapter, which did end a chapter in Mormon’s plate text, we have the conclusion of a year in which contentions had begun. In the beginning of this chapter we have the beginning of the next year, and the mention of contention. Why were these two verses separated? The year marker is a convenient place for Mormon to break a narrative, and the rapidly approaching time of the Messiah’s gives Mormon increasing reason to make not of the time. The nature of this timeline is important to understand the events leading to the arrival of the Atoning Messiah.
Apart from the convenience, however, the previous chapter was about the specific prophecy of Nephi and its aftermath as it related to Nephi himself. In this chapter, the focus is not on the prophet Nephi, but rather on the events themselves, the events that begin to fulfill the prophecies of destruction that were part of Nephi’s message.