According to Hugh Nibley, in an old Saints Herald, Emma Smith was being interviewed after the death of the Prophet. She said when they got to this passage (Joseph Smith was translating with the seer stones), he looked up with surprise and said, "Emma, did Jerusalem have walls?" He didn't even know the city had walls. He didn't know anything about what he was writing here. Yes, Jerusalem had walls. [Hugh W. Nibley, Teachings of the Book of Mormon, Semester 1, p. 159]