In response to Sung Chan Lee's comment of July 6, 2021
I, of course, agree with you Sung Chan Lee.
South Korea (SK) deploying its KSS-3 ballistic missile submarines shows an intention to eventually arm the ballistic missiles with a deterrent warhead - which can only be nuclear.
SK is also signalling the US that it is essential the US maintain the "nuclear umbrella" - a continuing willingness to defend SK with nuclear weapons.
If the SK warheads remained just conventional high explosive this would confuse North Korea (NK) (and everyone else) as to why SK is building ballistic missile submarines of 3,500-4,000 tonnes armed with ballistic missiles with a TOTAL high explosive throw-weight of only 6 to 10 tonnes.
Even if a tonne of a SK conventional warhead equalled 2 tonnes of old fashioned TNT (TNT being the standard for measuring nuclear yield equivalent ) then a one tonne SK warhead would have a yield of only 0.002 kilotonne.
Meanwhile a single NK SLBM warhead (weighing one tonne) may have a yield of 100 kilotonnes (the usual 2 stage "Teller-Ulam" thermonuclear weapon minimum) and maybe up to 500 kilotonnes = half a Megatonne.
So SK is hedging. If the US does not plainly indicate it will defend SK by nuclear means (principally against NK but also against China and Russia) then SK's KSS-3s constitute a very viable nuclear weapon delivery platform.
Regards
Pete