My blog post on Come Follow Me: Alma 53-62
Excerpt: The sons of Helaman
The Ammonites, those Lamanite converts that swore to never take up weapons of war again, were ready to break their covenant of peace, in order to help rescue the Nephites. The prophet Helaman, however, would not have them break their covenant. Instead, a different solution was brought forth. The children had not made the oath to bury their weapons of war.
Note here that the Ammonites could not really be called pacifists, as they are willing to recognize the necessity of arms to defend oneself and home, nor had they taught their children to refuse to fight. But their covenant was instituted for a higher and different purpose.