You do know where the bohai sea is? It's surrounded by China. If you approach the gap, you'll be shot at from both the NK and China directions, by land based missiles, not even counting the northern fleet and air assets which beat ROKN in both quality and quantity.
Bohai sea is not a place even 5 US carrier groups at once would survive if they sail straight in.
Yeah I know where it is. Northwest of Incheon, where a major ROKN naval base is. I have never said that the ROKN will go into the Bohai Sea. The US should be commanding them to block any PLAN naval vessels in the Bohai Sea from exiting the Bohai Sea, and then going south to link up with the rest of the PLAN in the other seas. Plus, with the long-ranged missiles in their arsenal, the US will be more than tempted to command the ROKN to fire at Chinese coastal targets. Remember that I emphasize US command. I'll get back to it below.
And how stupid is it for SK to commit an attack against well defended Chinese core territory with a couple of ballistic missiles when China has tens of thousand guns aimed at their population centers? SK attack on civilians in Liaoning sounds like a way to create a tragedy for SK on the scale that anything imperial Japan did to them would be forgotten in comparison.
This is not what SK would do on its own. It is not even in their interest to fight a dumb losing battle with China. But, it is highly likely that the ROKN will be placed under the command of the USN 7th Fleet Naval Command in Yokosuka, Japan. Why? Isn't it already obvious that SK is not a sovereign country? It is a vassal state of the US along with Japan. Even someone as progressive as Moon couldn't steer SK out of this situation. The SK population is already knee-deep in submitting to the US. Then came Yoon, who is already accelerating SK's submission to the US, undoing years of Moon's work. Yet the general SK populace appears to be more than happy with this development. SK have submitted their armed forces under US command before in the Korean War. Why would they not do the same again in a future US war with China?
Do you think the US would give a damn if thousands of South Korean sailors go under the sea? Do you think the US cares if China retaliates and burns Seoul and Incheon? SK is also rabidly anti-China, and the US is giving them a 'divine war' to bring China down. Can we trust SK to grow a spine and defy US orders?
SK could indeed participate in an attack on China, but they would still have to do it in a way that has a brain. That means exfiltrating navy from the 1st island chain where China has total control immediately. Such as going to Guam or even further out, linking up with US forces there.
I don't see this as likely. If the ROKN is pulled to Guam, that leaves Seoul and the rest of South Korea badly underdefended from the seas. The ROKN will be badly needed to defend Seoul, Incheon, and the South Korean homeland from Chinese retaliatory strikes and possible North Korean coastal raids. The USN would also want to use the ROKN as a vanguard force to hit PLAN forces in the northern ECS.
Launching SLBM at China is really dangerous because the launches could be conflated for Ohio class launches, but ROKN would be able to add their cruise missiles to America's.
Unless the Hyunmoo-4 was launched from the ECS. It'll be too near to be interpreted as a Trident missile. Besides, the ROKN have Hyunmoo-3 cruise missiles which I think will form the bulk of their land attack option. Hyunmoo-3 strikes should be expected to compliment the larger-scale cruise missile attacks by the US on the Chinese coast.
Even then, there's the real question of how SK homeland will survive once the inevitable counteroffensive comes. The ROKN could run away and survive, but giving up the peninsula for the ROKN doesn't seem a good deal either for US or for the SK regime.
I don't know how long SK will survive in a war with China. But we should expect them to at least give a decent fight. Even after their airforce and navy has been decimated. Any war with China for them is gonna be treated as existential, because of their identity crisis.
The ground war with SK, I suspect will be grueling, because they have in place a long-running conscription and military-readiness system. They also happen to have one of the most racist, hate-filled populace in Asia. We should remember that SK troops have done some ugly things in the Korean War and the Vietnam War. They ultimately cannot prevail against China + North Korea, but we should not underestimate their ability to fight.