Mormon indicates that the Lamanites have moved into the land northward to preach, and then indicates that Nephi and Lehi go with them. This is a continuation of his emphasis on the land northward that we saw in chapter 3. It is part of Mormon’s editorial purpose to make sure that we understand that the gospel has been preached in the land northward because he will use that information when he ties the destruction of his people to those who come from the land northward.