The Gadiantons regroup and prepare for another attack. Now that they have suffered a defeat at the hands of the Nephites it is probably even more desireable to conquer them. Such a powerful enemy so close by could mean continual trouble. The Gadiantons do not attaché for over two years. While Mormon does not know anything of the Gadianton activities in those two years, we can be reasonably certain of some of those activities based on the nature of the attack in the twenty first year.
When the Gadiantons return, they return to lay siege to the Nephites. Since one of the problems of Giddianhi’s invasion was the unexpected failure of local supplies, that mistake would not be made again. If a siege was planned, then provisions to supply the Gadianton army during the siege would have been accumulated, and the two year hiatus was, in all probability, used to gather as many provisions as possible for the coming siege.