Helaman’s attack changes the objectives of the Lamanite troops. They may no longer commit fully to fighting Antipus because they must also deal with Helaman. A standard tactic for a numerically superior force would be to extend the front line so that a greater numbers of fighters could engage at one time, leaving the smaller force at a real disadvantage. Helaman’s attack forced the Lamanites to immediately allocate fighters to the rear battle line as well, compacting the line of engagement, and evening out the forces that would come face to face.
Text: Alma 56–58 reads as a quotation from Helaman’s letter, except for this verse, which reads: “… Helaman came upon their rear.… ” If this is a quotation, it should read “I.” This kind of transcription error happens when the scribe mentally shifts from copying to describing. It could be an original scribal error when the letter was inscribed on the plates of Nephi, or Mormon’s or Joseph’s error. Tvedtnes attributes it to Mormon who “simply slipped into the role of historian and, in retrospection [sic], employed third person this one time.” I agree, since this error requires some familiarity with the text, terrain, and battle, making Mormon (or the plates of Nephi scribe) a more likely source than Joseph Smith.