With the power to force the dissenters to either join with the rest of the Nephites, or be killed, Mormon fought what was essentially a civil war, but one in which appears to have had significantly fewer numbers. His civil war ended much more quickly than the Civil War that the United States had to endure.
Mormon writes these passages as though the defeat of the armies was the total defeat of the kingmen, but that will not be the case. This is a temporary victory as we will see later in Alma 60.