The whole thing only costs $2.99, but I'll give you the answer from my Korean Peninsula Sourcebook for free.
"As Soviet and Allied units clashed in North Korea, the Stavka, responding to the perceived existential threat posed by NATO forces crossing the Soviet frontier in the west, roused the dozing genie of nuclear warfare, unleashing it once again on mankind, first, haltingly in Europe, then, on a massive scale in East Asia. Of all belligerents, China was hit hardest; much of the PLA was vaporized in the first week of the atomic barrage. Under heavy nuclear and conventional attacks, the Northern Chinese Front disintegrated. The headquarters of the Chinese 28th Army was obliterated by a tactical nuclear strike, and the remains of U.S. 2nd ID found themselves on their own, cut off from the rest of 8th Army.
"On 10/21, 'Tropic Lightning' was hit by no less than six tactical nuclear weapons; it was subsequently overrun and annihilated by Soviet mechanized forces- only 1,000 survivors from the 25th ID made it back to Allied lines."
[The above two paragraphs are based on specific v1.0 canonical references. The next two were approved by Marc Miller.]
"Through September and October, U.S. 8th Army countered Soviet tactical nuclear strikes with several of its own, buying some breathing room and inflicting heavy casualties- the Soviet 12th MRD, caught in a bottleneck at a river crossing, was annihilated by a well-placed Lance battlefield nuclear missile.
"In an attempt to end the campaign in one fell swoop, or at least prevent a timely Allied counteroffensive, Stavka authorized the destruction of several strategic targets in the Republic of Korea: Seoul, the capital city, Incheon, a major port close to the Allied main line of resistance, and Kunsan, another west coast port and home to a major USAF airbase (and the only nuclear weapons storage site in the ROK), were all slated for destruction. On November 4th, a single SS-17 Spanker ICBM launched from southern Siberia released four MIRVs high over the Korean Peninsula. 500 kiloton warheads detonated over Seoul, Incheon and Kunsan, wreaking havoc and killing, in total, hundreds of thousands of civilians. Fortunately, the fourth warhead (also targeting Seoul) failed to detonate.
"To impede the arrival of additional reinforcements from the U.S.A. by way of Japan, the east coast ROK port cities of Busan and Ulsan were also targeted for destruction. In the early dawn hours of November 8th, the Echo II class SSGN, K34, surfaced in the Sea of Japan and launched two nuclear-tipped P-1000 Vulkan cruise missiles, one each at Busan and Ulsan. Several minutes later, the 350 kiloton warhead aboard the first P-1000 detonated over Busan, wrecking the port and badly damaging the eastern half of the city. The missile targeting Ulsan suffered a critical engine failure soon after launch and crashed into the sea well short of the Korean coast (the warhead did not explode). A JDF P-3 Orion, on routine ASW patrol over the Sea of Japan, spotted the smoky missile launch signatures on the western horizon and closed at speed to investigate. K34 had difficulty retracting one of its missile launch tubes, delaying its escape. It was attempting to submerge just as the JDF P-3 arrived overhead. The P-3 dropped two Mk. 46 homing torpedoes, both of which tracked and hit the crash-diving K34, sinking it along with all hands.
"The United States responded to the strategic nuclear attacks on South Korea by obliterating the Soviet Union's Pacific port of Vladivostok with a Trident SLBM. As the year wore on, use of nuclear weapons by both superpowers expanded. U.S. military bases in Japan and the Philippines were destroyed; U.S.8th Army was becoming increasingly isolated."
Bergesen, Alf R.
The Korean Peninsula: A Twilight 2000 Series Sourcebook
2nd Edition
Far Future Enterprises, 2018
Watermarked PDF
https://www.drivethrurpg.com/product...book?src=fp_u5