After Moroni had pondered over the insulting letter from Ammoron he developed a completely new approach for the recovery of the Nephite captives which the Lamanites were holding prisoners.
It is clearly evident that Moroni's patience had been completely exhausted by the deadly war which was being prolonged year after year. Moroni had reached the conclusion that the only way to save the further shedding of blood was to wage an all-out war of death to the enemy until they surrender. This demonstrates the fact that Moroni had concluded after Ammoron's letter that there was no hope for peace in any other way.
Moroni knew exactly how he would proceed to liberate a large segment of the Nephite captives without have to exchange any Lamanite prisoners, which would only add to Ammoron's strength. Here is an account of how he proceeded.