That doesn’t make any sense whatsoever. They can hit any part of SK with a missile launched from NK. Why would they need to use a sub launched missile to attack SK?
Sub launched missiles w nuke warheads are solely for the purpose of hitting the US mainland. But all their subs are diesel powered and need to surface regularly to charge batteries, so I think they’d have a hard time of a sub sneak attack on the US.
Read the article.