The campaign of the previous year was inconclusive. The Nephites attempt another campaign in the very next year. That one also fails, though they do inflict damage on the Gadiantons. In just a short time these Gadiantons have tremendous numbers. This is an important piece of information, because large numbers of people must require certain kinds of an infrastructure. To feed large numbers of people one must have an agricultural base. It cannot be done with a hunting base alone, and could not be done on the basis of theft either. The only way that large numbers of people in a concentrated location can be fed is through agriculture.
The presence of agriculture requires permanence of residence. One cannot move planted fields from one place to another. The effect of Mormon’s information that there were large numbers of Gadiantons is to confirm to us that they must have a city. They must have an organization that can not only feed, but also defend, a large number of people. Such things require a high degree of social organization, and argues for an incipient city-state rather than a band of guerilla robbers.