The Lamanite king had been lost and was presumed dead. That situation would require that a new king be selected. The battle was lost when the king was lost, but that does not mean that the entire war was doomed. With a new king and no other ill effect from their defeat in battle, they might be expected to return to their original purpose. The oath had been breached, and the women were still missing. Thus, it is not surprising that the Lamanites were preparing for another assault on Lehi-Nephi.
In this situation, Gideon sees the fulfillment of prophecy. They will all be killed unless, as Gideon proposes, the reason for the war can be eliminated. The conflict is justified only because of the breach of an oath. If Limhi’s people did not break their oath, then there is no reason for war. The Lamanite king’s pleading for the Limhites will satisfy the claims of honor by declaring the Limhites innocent of oath-breaking.