[Travis McGee]

The ROK needs to send a nasty “accident” to the north.

Deniable, of course.

[ErnstStavroBlofeld]

I agree

[usurper]

I would view any NK sub in SK or international waters as a hostile and sink it. I would not claim credit and would deny any involvement if NK complained about missing subs.

This would put NK in the embarrassing position of having lost subs and crews and no evidence to point the finger at SK. Our subs did a lot of work during the cold war we still don’t know about.

[TigerLikesRooster]

Unannounced nasty accident SK don't claim as its own as NK did. That would be what you need to in this kind of situation.

I was thinking something like blowing up the bridge over Yalu if possible. It would send message not only to Pyongyang but also to Beijing.

However, if that cannot be done, alternative is to make some strategic change. It does not have to be loudly public. Start SK’s own project for medium-to-long range missiles. Begin with the one which has the range of 2000 km. That would put Beijing and Tokyo within the range. It would spur Japan to match SK’s move, then Chicom would suddenly face the prospect that numerous missiles of SK and Japan are pointing at them. This would make China rethink its habit of scuttling any attempt of putting serious pressure on N. Korea, by providing back channel lifeline to N. Korea.