[wiggen]

But they can’t fire while digging out so they would be out of commission.

[Brad from Tennessee]

That's true. And some of the gun and rocket crews would be killed in the first airstrike. But with the chemical and other ordnance described in this article even a few salvos would do a lot of damage. The strategy would be to provoke an invasion by South Korean and U.S. forces, the rationale being NK has a better chance defending against an invasion than mounting one. They might hope this would rally the population and even draw China into the fracas like 1950.