In the worst-case scenario, experts even wonder whether this is the start of a once unthinkable chain of events that could end with a return to inter-Korean conflict, perhaps even with the North invading the South -- though most see this as highly unlikely.

As professor Andrei Lankov of Kookmin University puts it, the lesson North Korea has learned from Russia's war in Ukraine, is simple:

"Never, ever surrender your nuclear weapons."

A nuclear lesson, from Ukraine to Saddam and Gaddafi

Moscow's invasion of its neighbor has reinforced a message that has been playing on Pyongyang's mind for decades, Lankov said.

When Ukraine was part of the USSR, it hosted thousands of nuclear warheads. It voluntarily handed these over to Russia after the Soviet Union collapsed in 1991, as part of a 1994 deal with the United States, United Kingdom and Russia which would guarantee Ukraine's security, a deal known as the Budapest Memorandum.

Ukraine now finds itself under brutal attack from the very same country that signed the deal to protect its sovereignty -- one that now repeatedly refers to its nuclear arsenal to warn the West off intervention.

Would Moscow have invaded if Ukraine had kept its warheads?

Most experts -- and most likely Pyongyang too -- think not.

"Now (the North Koreans) have got yet another confirmation (of this lesson) after Iraq, after Libya," Lankov said.

Pyongyang regularly uses the experiences of Saddam Hussein and Moammar Gaddafi, the former leaders of Iraq and Libya, to justify its nuclear program, both to its own people and the world. Both strongmen leaders lost their grips on power -- and ultimately their own lives -- after their own nuclear ambitions came grinding to a halt.

The Russian invasion will bolster that narrative, but in doing so it could also have a "very negative impact" on the mind of North Korea's own strongman leader, according to Lee Sang-hyun, president and senior research fellow of the Sejong Institute.

He says Kim is likely to respond in only one way: by becoming "even more obsessed with his nuclear weapons and missile capabilities."

Pyongyang's carte blanche

Even before the invasion, North Korea had shown signs of ramping up its nuclear ambitions.

And commercial satellite images suggest Pyongyang is trying to restore access to its Punggye-ri underground testing site, according to South Korean officials and think-tanks.

Against this background the Russian invasion -- and the international sanctions that followed -- have created a "perfect storm" of conditions for Pyongyang to operate in, analysts say.

"There are some interesting, perhaps unintended consequences for the Western response against Russia in particular, which is that a Russia that has been completely isolated from the global economy and put under tremendous sanctions pressure. I think it has very few incentives to enforce sanctions against North Korea," said Ankit Panda, a senior fellow in the Nuclear Policy Program at the Carnegie Endowment for International Peace.

A clear split among United Nations Security Council permanent members -- Russia and China on one side, the UK, US and France on the other -- means any unified decision to punish North Korea is impossible.

"It's quite clear that China and Russia will block additional sanctions and frankly it's not quite clear, what else can you possibly sanction," Lankov said.

Even a seventh nuclear test may not provoke the usual negative response from Beijing, "China is not going to be happy enough about nuclear tests, but they will swallow it," Lankov said.

Cashing in with an old friend

If anything, North Korea may even benefit financially as other countries boycott Russian oil and gas. The cash-strapped country would be more than happy to take up some of the slack, potentially at a discount, and deal with a Russia no longer constrained by US-led sanctions against the North.

"I think that Russia is going to provide more economic support and energy support to North Korea," said Ramon Pacheco Pardo, the KF-VUB Korea chair at the Institute for European Studies of Vrije Universiteit Brussel.

"Oil and gas, certainly but it could also include food... fertilizers, it could be all sorts of economic aid North Korea wants."

That Pyongyang would side with Moscow in a new world order is not a surprise.

Relations between the two countries were forged by the Korean War of 1950-1953, and they shared a communist ideology for decades.

The former Soviet Union was a major benefactor to North Korea, financially propping the Kim regime up. While that task has now transferred to China, the return of Russia to strongman rule under President Vladimir Putin has put a new shine on the relationship.

"(Pyongyang) were sort of disgusted about the democratic and liberal or semi-democratic, semi-liberal Russia which used to exist, and they basically greeted Vladimir Putin as a leader who was driving the country into the right direction," Lankov said.

Kim's fleeting dance with the US -- holding three meetings with former President Donald Trump that ultimately yielded little -- only reminded him his more natural and lucrative allegiances remain with China and Russia.

Pyongyang for its part has made clear where it places the blame for the war in Ukraine. "The root cause of the Ukraine crisis lies totally in the hegemonic policy of the US and the West which indulge themselves in high-handedness and arbitrariness towards other countries," its Foreign Ministry said.

Would North Korea invade the South?

Since Russia's invasion, North Korea's rhetoric towards South Korea has changed.

Last month Kim's sister, Kim Yo Jong, warned that if South Korea was to confront the North militarily its army would "face a miserable fate little short of total destruction and ruin."

Threatening language from Pyongyang is nothing new -- a US official once described being insulted publicly by North Korea as like a "badge of honor."

What is new is that since the invasion, experts like Lankov have been asking whether North Korea would consider an invasion of the South again -- more than seven decades after its invasion in 1950 sparked the Korean War.

That question has for years been dismissed out of hand. Most experts still see the changes as negligible, but the fact it is even being discussed is noteworthy.

"North Koreans are probably dreaming again about something that (they) used to take seriously, but in recent decades nearly forgot. That is conquest of the South," Lankov said.

For now, the idea seems fanciful. But the future is another matter.

"Maybe, just maybe, the American President of the year 2045 or 2055 will not risk San Francisco in order to save Seoul," Lankov said. "(By then) North Koreans could use ICBMs, maybe nuclear armed submarines to (terrify) Americans, to blackmail Americans out of the conflict."