Attacking a fortified position that was defended with a large army meant that Teancum’s army was probably insufficient to take the cities. Therefore, the decision was made to attempt to keep the Lamanites within the places they had won, but not be able to increase their holdings. This would have been less than a siege, and more of a containment.
Teancum’s desire was that he would hold his positions and keep the Lamanites from expansion, but would not attempt to drive the Lamanites out of the land until Mormon could send reinforcements.