At the end of the previous chapter in our modern edition, we learned that many prisoners were taken. There was no chapter break in the 1830 edition, so these verses discussing what was done with those prisoners were part of the original story.
Rather than lock the prisoners away, they were organized into forced labor. The first requirement was to bury the dead. In previous engagements, the Nephites had thrown the Lamanite bodies in the river. Since the Lamanites were the ones doing the burying, they were allowed to provide the same burial for both their dead and those of the Nephites.
There was no indication that any kind of oath was taken of these prisoners, and it was therefore prudent to have Nephites standing guard over them. Verse 3 picks up on the labors of the prisoners, which will continue in the next verses. That makes verse 2 feel like an interruption in the story. Rather than an interruption, however, it is a conclusion. Verse 2 finishes the story of what Chief Captain Moroni did, which was to install Lehi in Mulek. As a seasoned leader, Lehi significantly improved the defensibility of Mulek.