The commentaries explain that Ammon's core sin was glorying in its own strength. Whether in their fertile valleys, their wealth, or their fortified cities, they arrogantly believed they were untouchable. Their boast, "Who shall come unto me?", reveals a prideful self-reliance that ignores God's ultimate power. This serves as a timeless warning against placing our ultimate trust in worldly security, wealth, or position instead of in God.