Alma 53:16 - 53:23
Alma 53: 16 But behold, it came to pass they had many sons, who had not entered into a covenant that they would not take their weapons of war to defend themselves against their enemies; therefore they did assemble themselves together at this time, as many as were able to take up arms, and they called themselves Nephites.
Now even though the people of Ammon had made this covenant not to ever take up arms again against anyone for any reason, their sons had not. And the sons seeing the grave danger of the Nephites and of their own parents, said they would take up arms to defend the Nephites and their own parents. And as many were of sufficient age gather themselves together and now called themselves Nephites to unite themselves with them.
Alma 53: 17 And they entered into a covenant to fight for the liberty of the Nephites, yea, to protect the land unto the laying down of their lives; yea, even they covenanted that they never would give up their liberty, but they would fight in all cases to protect the Nephites and themselves from bondage.
They now entered the same covenant that Moroni was demanding of all Nephites, that they be willing to give up their lives to protect their freedoms, their country and to fight the Lamanites who wanted to enslave them.
Alma 53: 18 Now behold, there were two thousand of those young men, who entered into this covenant and took their weapons of war to defend their country.
There were 2000 young Ammonites who had entered into this covenant and were ready to fight.
Alma 53: 19 And now behold, as they never had hitherto been a disadvantage to the Nephites, they became now at this period of time also a great support; for they took their weapons of war, and they would that Helaman should be their leader.
This increase in the Nephite army with these 2000 young fighters came at an opportune time for the Nephites as they were low in numbers of available fighting men. As to their leader and commander they asked for Helaman.
Alma 53: 20 And they were all young men, and they were exceedingly valiant for courage, and also for strength and activity; but behold, this was not all—they were men who were true at all times in whatsoever thing they were entrusted.
These young Lamanite men were wonderful examples to the rest of us. They were valiant in doing just what they were asked to do. They were in great physical condition and were motivated to fight because they were wise enough to see the danger if they did not.
Alma 53: 21 Yea, they were men of truth and soberness, for they had been taught to keep the commandments of God and to walk uprightly before him.
These were men that were living the gospel to its fullest extent even though they were very young likely were just like any teenager. However, when it came to living as they should, they had little equal and they certainly did not want disappoint their parents and the Nephites as a whole. These were men that could be counted on when the need might be the greatest.
Alma 53: 22 And now it came to pass that Helaman did march at the head of his two thousand stripling soldiers, to the support of the people in the borders of the land on the south by the west sea.
So with Helaman at their head these young boys now called men and will be referred to as “Stripling Warriors” set off for the border of the land in the south by the west sea.
Alma 53: 23 And thus ended the twenty and eighth year of the reign of the judges over the people of Nephi.
And that's the way it was at the end of the 28th year.