For all the heartburn about North Korea, many experts feel the greatest danger of nuclear war remains one between India and Pakistan.
Why? Their nuclear doctrines are downright hot-headed. Pakistan, intimidated by the much larger conventional forces of its neighbour and arch-rival, states that if Indian forces charge over the border, it would launch a nuclear strike on its own soil against the invaders.
Pakistan argues this would be self-defence, not a nuclear attack on India.
India of course sees it differently and vows it would retaliate with nuclear counter-strikes.
India moreover says it might retaliate with nuclear weapons if Pakistani terrorists - regarded as proxies for their country's intelligence agencies - ever carried out another Mumbai-style massacre. That is more than a remote possibility.
"It's scary. The last time there was a conflict, Pakistan devolved launch authority down to the field commander," said John Carlson, an Australian former nuclear negotiator now serving as a counsellor to the Washington-based Nuclear Threat Initiative, a group that works to reduce the risks posed by weapons of mass destruction.
"They say they've got better command and control now but I don't know how much confidence you can have in that."
If that's not enough, India's real nuclear rivalry is not even with Pakistan. It is with fellow rising power China. China in turn has nuclear deterrence strategies against the two established Cold War giants, the US and Russia.
The world, in short, is getting more complicated.
Nuclear weapons have been part of the strategic landscape for more than 70 years. But for most of this time, the standoff was between two superpowers, the US and the Soviet Union. Then for a while there was one, the US.
That's now changing to a world strategic boffins call "multipolar", where power is fragmenting and redistributing. And some experts are wondering why this isn't prompting a more urgent conversation about what it means for nuclear weapons and their proliferation.
David Cooper, a long-serving former Pentagon official who is now a professor of National Security Affairs at the US Naval War College, calls it "trans-regional nuclear arms racing", something he says "we have never seen before in the relatively brief history of the nuclear age".
"And we don't know what deterrence or arms control would look like in this new context of potential nuclear multipolarity, which could involve simultaneous, and interconnecting, nuclear arms races within and across regions, because we have never been in a multipolar world since the dawn of the nuclear age," Cooper said.
"This would be completely new if it comes to pass. That's something we need to start thinking about."
The world's estimated 15,000 fusion and fission bombs remain the only weapons stockpile that poses a truly existential threat to humanity. The most powerful nuclear weapon ever tested, the Soviet "Tsar" bomb detonated in 1961, had nearly 5 million times the yield of the most powerful conventional bomb, the US-made MOAB.
The current crisis of Kim Jong-un's nuclear program, and the postponed problem of Iran, are symptoms more than drivers of the fears of a more nuclear-armed world.
No doubt they are pressing. Foreign Minister Julie Bishop this week expanded on remarks she made in a recent opinion article for Fairfax Media, expressing concern that an unchecked Kim regime would encourage proliferation elsewhere.
"If North Korea is allowed to achieve its aims and ambitions and increase its leverage as a de facto nuclear power, it could give strong temptation to others to follow the path. They would see that North Korea's success as confirmation that covert development program can be achieved," she said.
"There are numerous countries around the world - I don't want to specify any particularly but there are a whole raft of countries - that don't have the same view of nuclear non-proliferation as we do. And those who may well be harbouring nuclear weapons capability will be observing a North Korean example very closely."
Bishop also pointed to the sensitive question of whether a fully nuclear North Korea might push South Korea and Japan to seek their own nuclear capabilities.
"While they are obviously heavily reliant on the US umbrella of deterrence, it would compel them to reconsider their own defence," she said, though she added she was confident the current collective strategy would strengthen rather than weaken the umbrella of deterrence the US provides its allies.
The Iran nuclear deal, meanwhile, has kicked the can down the road on Tehran's ambitions, according to many experts. Bishop said this week the deal was far from perfect, though she strongly warned against US moves to withdraw from it.
Experts fear that if Iran eventually goes nuclear, then Saudi Arabia, Turkey and possibly Egypt may feel compelled to join the club.
These are just the immediate knock-on effects of the current challenges. But some long-serving nuclear theorists are worried about deeper and more fundamental changes.
Nuclear theory is complex, indeed arcane. But it's important to understand why countries get nuclear weapons.
The Americans and Soviets amassed giant stockpiles during the Cold War to deter one another from what could have been a prolonged nuclear fight. NATO meanwhile positioned nuclear weapons in Europe to overcome the Soviets' conventional military advantage on the continent and deter a land invasion.
Cooper's point is that in a multipolar world, those relationships are becoming interlocked across regions. The countries that are rising in the world pecking order, such as China and India, and those that are trying to revise it, such as Russia, are prominent nuclear powers.
"They are not necessarily satisfied with a nuclear status quo in which the United States is first among a static and stable group of established nuclear powers," said Cooper, who was speaking in a personal capacity. "This is evident because these countries are not seeking opportunities to reduce their nuclear arsenals but quite the opposite, although this may be as much about them warily eyeing each other as the United States."
Carlson similarly said not enough attention was being paid to the triangle between China, India and Pakistan.
"There is the possibility that things could start to get out of hand if you've got arms races involving India, Pakistan, China. It could be very difficult to control," he said.
Meanwhile Russia is cheating on and may even pull out of the Intermediate Range Nuclear Forces Treaty because it only applies to the US and Russia - a relic of the old bipolar world of arms control. Russia needs intermediate-range missiles to counter China, which isn't constrained by the ban and is going "pedal to the metal" on such missiles, Cooper said.
The old nuclear mechanisms such as the Non-Proliferation Treaty have served the world well, Cooper said. But they "may be on the brink of not being operative any more".
He described the latest UN attempt at a total nuclear ban - widely regarded as hopelessly quixotic - as an example of the woefulness of modern multilateral efforts.
"I consider it actually quite worrying that international efforts in these areas have become conspicuously unserious," he said. "That makes me nervous."
Carlson was similarly scathing. Instead of going for something achievable, perhaps a treaty agreeing to no first use of nuclear weapons, the countries leading the effort, which included Brazil, Mexico, Ireland and Austria, "just wanted to make a political statement".
"It couldn't have been worse ??? It was just totally irresponsible," he said.
Disarmament needs to be stepwise to be realistic, most experts say. But it also needs to be led by the major powers, which isn't happening in this era of rivalry. Hans Blix, the veteran weapons inspector who famously clashed with the Bush administration over its claims of Iraqi weapons of mass destruction, told Fairfax Media that existing disarmament agreements were in danger.
"My own view is that the great powers must strive to get back to detente," he said. "We should not any longer sit puffing a big cigar telling the unruly children of the world to stay away from cigarettes."
Cooper said much responsibility rests with China, given its centrality to the new strategic geography. Though officially it has fewer than 300 warheads - a fraction of the roughly 7000 held each by the US and Russia - China has never been transparent and that is a serious problem, he said.
"The first step of any serious arms control process is baselining. What have you got, how many and what types? And then let's start talking about if you cap or reduce those, then I will cap or reduce these.
"We don't even know what the Chinese have because they won't talk about it."
Yet without at least China, the US and Russia on board, any kind of new disarmament efforts would be doomed, he said.
Not everyone thinks that multipolarity will be worse than the Cold War.
"People have been saying that we're going to have widespread proliferation for decades now," said Jim Walsh of MIT's Security Studies Program. "And in every decade they've got it wrong. If you look at the rate of proliferation, the number of new nuclear weapon states per decade peaks in the 1960s and it's gone down every decade since."
There is another take, which is that, managed right, nuclear weapons provide stability and deter conflict. Many point out that the US nuclear umbrella has probably done more than anything else to stop proliferation by dissuading US allies to seek their own weapons - even Australia.
Stephan Fruehling, a defence scholar from the Australian National University with deep expertise in nuclear theory, said that as conventional military power shifts to Asia, the US will probably have to return to relying on its nuclear arsenal as a stabiliser.
"As China in particular but also Russia in Europe starts to gain at least regional conventional superiority, I think the West and the US will look more to nuclear weapons to counterbalance that," he said.
That will mean a more versatile stockpile including smaller "tactical" weapons - "essentially what we did in the Cold War", Fruehling said.
This is not a bad thing, he adds. Without credible US nuclear power in Asia "then you could well see proliferation cascades", such as South Korea and Japan going nuclear.
There are signs of this already. US-South Korean talks on Friday were expected to canvass the return of tactical US nuclear weapons to the Korean Peninsula.
Similarly in Europe, NATO's language has returned to an emphasis on nuclear weapons since Russia's invasion of Ukraine, Fruehling said.
"Ultimately the role of nuclear weapons is to deter great power war," he said. "And it's great power war which has historically been the horrible thing. So if nuclear deterrence helps us prevent it ... that's a good thing."
The trade-off to making smaller nuclear weapons that are more credible is that they are more useable. That is dangerous, Carlson said.
"We're all better off if we conclude that these things aren't actually useable," he said.
A further complication is missile defence. China hates the US THAAD system in South Korea because though it is aimed at North Korea, Beijing perceives it as undermining its own nuclear deterrent. Carlson said this more than anything risked spurring an existing power to dramatically increase its stockpile.
"China sees it as potentially neutralising its deterrent and therefore is starting to think in terms that they may have to substantially expand their arsenal to overwhelm the defence. That's the biggest destabilising factor," Carlson said.
He thinks weapons states should work together on common missile defence as a joint project - though he acknowledges there won't be much enthusiasm.
Perhaps amid all these uncertainties the major powers will settle into their natural balancing act around a new nuclear status quo, Cooper said. But it could be a rough ride.
"That transition period to a new multipolar nuclear status quo - if indeed it ever comes to that, and given the horrific stakes - could be very dangerous if it is not carefully managed," he said.
"You've got to have nuclear stability work all the time with no miscalculations by anyone, ever, or you face the risk that the first wake-up call will be something really, really bad.
"I am not saying that this scenario is inevitable or even probable, but at the same time is by no means as implausible as many would like to believe."