In these two verses, the 1874 RLDS edition omitted the word again both times. Each instance of the word was restored in the 1908 RLDS edition. The again is fully appropriate since the earlier war between the Lamanites and the Nephites was initiated by Amalickiah, a Nephite dissenter who had stirred up the Lamanites (as described in Alma 48:1–3). In the end of that war, the Nephites prevailed and the Lamanites were forced to return to their own lands (as described in Alma 62:38).
Summary: Maintain the two instances of again in Alma 63:14–15 since the author wants the reader to connect the failed attacks described in this passage with the earlier ones instigated by Amalickiah, a Nephite dissenter.