Certainly Mormon understood the geography of his land. However, it is also tempting to note that Captain Moroni also paid particular attention to this narrow pass in his defense of the land of the Nephites. We see him using Teancum’s army to head off the people of Morianton in Alma 50:34, and Moroni again guards that pass in Alma 52:9. Since Mormon clearly admires Captain Moroni (naming his son after the great general) it would not be surprising if some of Mormon’s decisions were at least informed by his study of his hero’s defense of the land of Zarahemla.