S. Korea should show what a “crafty trick” it would be to destroy the thousands of artillery pieces the NORKs have pointed at Seoul. Threaten war? Reject “talks?” No problem! [Boom!] No guns.
That would put China in an awkward position. The Middle Kingdom hates to lose face, and would have to intervene in earnest. Better to have the Norks prove they’re not bluffing and give Seoul a bona fide casus beli, cross the border or something like that. Then China will be mad at the Norks over the face thing, and give only grudging help as required by their stupid pact, and a quiet green light to Seoul and Washington to smash all their guns.