SINGAPORE - Russia's invasion of Ukraine is "sadly… perhaps the final nail in the coffin" for the nuclear non-proliferation regime, former top diplomat Bilahari Kausikan says in The Straits Times' latest Conversations on the Future.
"The lesson… many countries have taken away from the Ukraine crisis is that you have to be able to defend yourself.
"And if your likely threat is a nuclear power… I don't think you can deter nuclear power by conventional means; that's a stark fact," said the former permanent secretary of the Ministry of Foreign Affairs - currently chairman of the Middle East Institute at the National University of Singapore.
In North-east Asia, China is modernising its nuclear forces, and North Korea is developing ICBM (intercontinental ballistic missile) capability, he noted.
It is a matter of time before questions will be asked regarding the efficacy of the United States' extended deterrence - the so-called nuclear umbrella, he said.
French statesman Charles de Gaulle was famously posed the rhetorical question whether, in the event of a nuclear war, New York or London would risk being destroyed to protect Paris, he recalled.
"The answer is obviously, no," said Mr Kausikan. "Similarly, I think quietly, much more quietly, people in Tokyo and so on will be asking similar questions. And I think the answers will be similar, and their actions will be eventually similar to what London and Paris did - acquire nuclear deterrents."
This does not mean Japan and South Korea are eager to become nuclear weapon states, he emphasised.
"I think they know it'll be very politically difficult, politically divisive," he said. "But (the threat from nuclear armed states) is not something that they can avert their eyes from, and hope it will go away. Because China is there. North Korea is there."
He added: "And while they will do everything they can to preserve (the US) nuclear umbrella, they know this is a delaying battle rather than something that can be decisively fixed. I don't know when, but I think the trajectory is set."
Nuclear weapons do not prevent conventional clashes or wars, but keep a lid on them, he noted.
In this respect, while the world will always be a dangerous place, a multipolar nuclear balance in the Indo-Pacific is "in a way a more stable world, because it will put an end, once and for all, once the weapons are developed and deployed, to any dream of hierarchy, whether by China or anybody else", Mr Kausikan said.
"It freezes the existing configurations," he said. "If I look at the countries involved, once you have this kind of complex nuclear balance, I think the tendency will be to reduce the temptation to adventurism."
And small countries would find that kind of multi polarity provides manoeuvring space, he added.
"In principle, this is a better world for small countries, provided… the process of getting from where we are now to where I think we will land can be managed."
The Conversations on the Future series focuses not on current news but on broader, and larger, long-term issues and trends.
Among the interviewees are Harvard professor Graham Allison, historian Wang Gungwu, science fiction writer Chen Qiufan, Yale Law professor Amy Chua and diplomat Tommy Koh.