“And behold, if ye do not this, I will come against you with my armies; yea, even I will arm my women and my children, and I will come against you, and I will follow you even into your own land, which is the land of our first inheritance; yea, and it shall be blood for blood, yea, life for life; and I will give you battle even until you are destroyed from off the face of the earth.”

I’m thinking maybe this is kind of like “If you are going to treat our women and children as if they are a threat, as if they are warriors, then maybe we will show you what a threat they are.” Maybe it is an insult, (i.e. even our children can take you out). Whatever it is, this comment is clearly meant to be shocking and provocative, which would indicate that arming women and children is something not usually done. So I’d be surprised if the women were really formally trained as warriors, but who knows? Its not entirely out of the question.

Also, maybe the reason the Lamanites would hold the women and children prisoner is because they were trying to bring the Nephites into subjection/slavery. Maybe these prisoners were the beginnings of such enslavement. Women probably had many desirable work skills which the men did not have. And if you have families they will breed future generations of slaves for you. There are two separate situations described in the Book of Mosiah where Nephites are enslaved by Lamanites, so there is a precedent for slavery as well. The Lamanite tradition was always that they were the rightful rulers of the people.