"Some 14,000 tubes of North Korean artillery are laid on their priority targets..." I have witnessed a "Time on Target" exercise involving sixteen battalions of Artillery. I was impressed, and I don't impress easily.
I cannot even IMAGINE what a million artillery rounds fired in the space of few hours would do. But I do know that I wouldn't want to be under them.
The most I've seen was about 10 battalions. And they used VT, which was most impressive. We later saw one regiment shooting DPICM (they don't do that too often in peacetime training) - and it was devastating. I cannot imagine what it would be like trying to defend a position under that kind of firepower.