US exerts more pressure on N Korea over some slight or other and halts energy aid, upsetting China, blowing detante out of the water, cranking up pressure on the penninsula
NK starts to publicly develop more Nukes, as this tactic worked in the past & the dear leader is now presiding over a starving nation - news leaks out of street disorder in NK due to apalling conditions.China demands Taiwan be reclaimed as part of the PRC and begins Naval "manouevers" within sight of taiwan shores.USA responsd with talk of econmic sanctions against China.Japan begins to rearm in earnest.
near collapse, the dear leader launches a single tactical nuke strike on Seoul + a 500,000 NK troops overrun the border.US intervenes with massive non nuclear response & with their "puppet

D ) South Korea Government forces, holding back the DPRK forces blitzkrieg.
China sends 1M troops and most of its Navy to back up the now struggling NK forces, and annxes taiwan with massive amphibious assault.US warns china not to advance into pennunsula and decides to destroy Pyongyang with small tactial nuke to halt momentum.
things get worse.