Verses 12-18 are a large set to keep together and understand, but they reduce to smaller units. In verse 12 Zeniff introduces the Lamanites as “a wild, and ferocious, and a blood-thirsty people, believing in the tradition of their fathers…” In the latter part of verse 12 through the end of 17 Zeniff is explaining what those traditions were. Finally in verse 18, Zeniff comes to the point, which is that all of this long-held hatred has fueled not only this war, but all of the dealings with the Lamanites from the beginning.
The description of the “tradition of their fathers” is a recounting of the history of Nephi and his brothers, Laman and Lemuel. We are familiar with that history, and it is quite likely that there was a tradition among the Lamanites that preserved an animosity towards the Nephites. In spite of this, there are some problems with Zeniff’s analysis of the situation. First, we must understand his discussion of Lamanite hatred in the context of an apparent war of destruction. Zeniff is certainly not favorably disposed toward the Lamanites at this point in time. However, we must remember that this is the same man who found “much that was good” among the Lamanites and did not want to destroy them when Zeniff first came to the land (see Mosiah 9:1). Clearly circumstances have changed his mind, but what does this have to do with the “tradition of their fathers?”
We must also remember that the people of Shemlon likely include those who were of the City of Nephi who remained with Mosiah and his people fled. Thus among the “Lamanites” we would have descendents of “Nephites.” At this point in the Book of Mormon, Lamanite and Nephite are more political designations than they are genetic/kinship designations. While descendents of Laman and Lemuel might have a hatred towards Nephites because of this “tradition,” it is less certain that a mixed population with adopted Nephites-become-Lamanites would have the same feelings towards the Zeniffites, who are arguably a new tradition.
The last clues as to what is going on is the opening statement and the conclusion Zeniff gives. Zeniff begins by calling the Lamanites bloodthirsty and wild. In recent history, the “bloodthirsty” Lamanites did kill some Zeniffites, but they paid heavily for that – and then did not retaliate for 9 years. Indeed, it might be argued that the Zeniffites were also “bloodthirsty” if the supposition is correct that they attacked hamlets rather than a standing army.
Zeniff is doing what all humans do. He is justifying his current position and indicating how he got himself into this fix. He sees all fault with the Lamanites, and blames both their tradition, and a long-standing “cunning” that was designed from the beginning to destroy the Zeniffites. Remember that this destruction is current, but contradicts the parallel statements of Lamanite-desired economic benefits from tribute upon the Zeniffites.
Finally, how is it that Zeniff knows so much about the reasons behind a Lamanite attack? Does he confer with king Laman? No. What we have are Zeniff’s suppositions, not facts. Those suppositions are filtered through the antipathy and distrusting separation between Lamanite and Nephite.