The Nephites are caught in a pincer, with strong armies attacking from both sides. The Lamanite army on the east does not even have to attack, but only to “harass.” They can stay in their fortified places and sally forth for short attacks that will occupy Teancum’s army. By doing so they may not capture any more ground, but the will occupy and army (and a valuable general) and keep that army from concentrating on the new attack in the west. Ammoron clearly understands that he is dividing the Nephite forces and thereby weakening their possible response.
“In the Ending of the Twenty and Sixth Year”
The events described have taken a year to unfold. Mormon does not give us more indication of the timeframes other than this marker. The death of Amalickiah comes in the last day of the twenty-fifth year of the reign of the judges, and the Lamanite retreat into the fortified cities happens the next day. Somewhere over the year the war bogs down around the now-Lamanite-possessed cities. Somewhere over the year Ammoron leaves to raise another army, and then returns to begin engaging Moroni. As the year ends, there is no conclusion to this war, only “dangerous circumstances.”