The north korean strategy is built upon the threat of a single massive missile barage that would do incredible damage to South Koreas major northern cities.
Basically a ton of missiles aimed at south korea, but once that salvo is done, they got nothing left but to pray that China comes to their rescue before the south koreans unleash the dogs of war.
Don’t get me wrong. There would still be a incredible number of South Korean civilians killed and destruction to its major cities from that single missile barage. But after the Norths one and done, from a protracted ground and air war perspective, it would be over faster than gulf war 2. A large hole would be punched in the DMZ and the north would be overtaken quickly. The only problem is if China decides to annex north korea once south korea begins to retaliate. Like Putin has done with Northern Georgia. I wouldn’t put it past the Chicoms to do this.
Missiles are only the half of it. Seoul is in range of something like 250 NK artillery tubes, most of which can fire chemical shells, and the density of NK artillery along the rest of the DMZ is not that much thinner.