The river again comes into play in the military situation. Rather than being able to flee as a unit, the Lamanites have had to form some smaller line to cross the river. Hence there are some on the west bank, some on the river, and when those who emerged from the east side of the river found land, they also found Lehi and his army. They are in an indefensible position.
Moroni does not pursue a war of destruction, but, upon seeing the inevitable defeat of his enemy, he stops the battle. There is no chapter break at this point in the 1830 edition, and indeed, the story continues with the immediate aftermath of halting the fighting.