Why does S Korea boost SSBN idea now and then

 South Korea’s latest float of a SSBN balloon has prompted comments from 2 Anonymouses over the last 2 days. My comments are in [...] square brackets  What do you think? Why does South Korea boost the SSBN idea, now and then?

 Anonymous A Commented:

 Just some meanderings relevant to current threads, with one small/simple point I think is being missed, I have been following this Korean debate re SSBN/SSN's and nuclear in general with great interest. 

As others have said, the need for a nuclear powered submarine platform is debateable in the comparatively small Korean theatre. The real standout feature of nuke boats is their ability to transit rapidly anywhere, which isn’t needed much in this context. There are other operational benefits of course, but also limitations, the applicability of both will vary greatly with to specific operational contexts.  

I think a crucial piece not been considered holistically by [South Korea] is the time-lining of systems.

Whilst I'm sure the South Koreans have the skills to design/build a compact reactor and associated drive-train for a nuke sub, that will undoubtedly be a big really LONG job. We could argue it endlessly. But unless South Korea has been progressing a nuke sub program in super secrecy for years to an already advanced prototyping stage (unlikely) then in my view they simply won’t be able to assemble a complete nuke sub powertrain in less than a decade, probably much more.

Again we could quibble, but the timescales for this would be long, even if they procured off-the-shelf (which I really doubt will happen - the political optics of that will be truly horrendous for all involved, with possible exception of Russia). The time required for South Korea to then understand/design/integrate/build/test/train etc, would still run to many years, still 10+ in my view.

On the other hand, as you and others have convincingly argued, a deliverable nuclear weapon may very well be able to be put together in a short time, 2 years feels feasible if they really go for broke on it.

Which means an SSB platform [like the KSS-3 already being produced] but with nuclear armed ballistic or cruise missiles, could/would be far more practical/useful in the short/medium term (2-15y) as it would be credible and relevant. Crucially, it would be a fully operational threat to adversaries, whereas any nuclear powered platform is a long, long way away.....

So in summary:

I think the SSN/SSBN system-skillset is probably a lower/longer priority effort. Also South Korea is focussing on getting the supporting systems and platforms for nuclear weapons delivery in place and ready, should South Korea decide at short notice to present a credible nuclear deterrent. It is backwards from how other nuclear nations did it, but is a clever hedging strategy combining elements of Israel’s Ambiguity with still being a Good NPT Citizen on the face of it - basically keeping all your options open! This gels with the ongoing KSS-3 plans and systems, including tangential systems, like cruise missile development etc.

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Anonymous B Commented:

 If an AIP SSK with cruise missiles is sufficient deterrent for Israel, how do you explain a South Korean SSN/SSBN program?  Who is it against?  Do they know something about the distance to North Korea that I don't know?  (Cruise missiles launched from dispersed South Korean trucks [or TELs] should be sufficient, especially for a second strike.)  SSN's would be even more strange.  Am I missing something about who the enemy is and where is the conflict expected to occur?

[Pete Comment: From what I’ve read South Korea has basically been talking about SSBNs. internationally recognized as the most secure second strike nuclear deterrent. Although misinformed journalists misconstrue that South Korea also wants SSNs.]

Speaking of who the enemy is, would it not be more logical for Australia to go to SSN's? You only have to refuel every few years, even if in France.  Not a problem if you have enough in rotation.

[Submarine Matters has published numerous articles for more than 10 years for and against SSNs for Australia:
1.  Australia’s vast distances would suggest SSNs but then again there is extreme cost. UK, India and France can only afford 6 to 7 SSNs Australia can afford only 3.
2. there is no forward base on Australia's east coast that would accept nuclear subs. 
   Australia's main East Coast Base is Sydney Harbour. Sydneysiders won't accept
   nuclear subs. 
3. Australia’s electorate are extremely anti-nuclear, (see point 2.) and half the job of SSNs is to defend SSBNs, which the Australian electorate and Navy don’t want. Just type in Australia SSN in the top left search box.]

Anonymous B Continues: The only thing I can imagine is South Korea signalling (to China) that they can also have a short notice nuclear breakout, but given US guarantees against North Korean nuclear attack, that would only be useful with respect to China.  That is the only opponent I see warranting an SSBN/SSN fleet.  This would indicate that South Korea is expecting long term pressure from China, along with a long term decline active US support [very true] or indeed support from any other quarter, such as Japan.  

In a case like that, the best policy would be "Smile broadly and build a big whopping stick".  Machiavelli (or me for that matter) would probably advocate such a policy, but such long term strategic policies are rare in democracies.