I used to think that North Korea could easily flatten Seoul, but it turns out that this really isn't the case.

The majority of NK's artillery is not long range and can't threaten the densest parts of Seoul; while those that are long range will be immediately targeted and destroyed once they begin firing. Then there are serious questions regarding the quality of NK's equipment and their troops, plus the fact that artillery on its own is not particularly lethal.

Finally, South Korean civilians in the part of Seoul most under threat are prepared for this attack and most every subway station can double as a bomb shelter.

Any NK artillery attack would definitely kill a substantial amount of civilians, but it wouldn't be 100,000s and it wouldn't destroy Seoul. The real wildcard is if NK uses chemical or nuclear weapons which changes everything.

There's a good summary of any potential NK attack on Seoul here: www.dailykos.com/story/2017/4/25/1656090/-North-Korean-artillery-and-the-concept-of-flattening-Seoul-a-breakdown