Just two months ago, Russian President Vladimir Putin and the leaders of four other states holding nuclear weapons released a statement agreeing a "nuclear war cannot be won and must never be fought".
Since then, a lot has changed. Putin has ordered an invasion of Ukraine, activated his nuclear deterrence forces, and signalled he is unwilling to back down from conflict until he achieves his goal of stamping out Ukrainian authority.
The decision to put his nuclear forces on high alert, the first time this has been done since the Russian Federation was established in 1991 and which Putin did suddenly and not in retaliation to any other nation also toying with the nuclear option, received widespread condemnation and raised concern Putin may go to extreme lengths to win his war.
Exactly what this new state of alert means is unclear to Western analysts given Russia's different defence readiness conditions, but it's thought by some that his forces are now at an "elevated" state of readiness.
But is it all bravado from the Russian side? Is Putin just trying to raise the stakes to strike fear in the Ukrainians and the West, hoping they will back down or give concessions, as the Ukrainian Foreign Minister suggested?
David Welch, an expert in international security at the Canadian University of Waterloo, told AM it comes down to a question of what Putin's mental state is.
"It's all sabre-rattling and not serious if Vladimir Putin is rational. If he is stressed out, emotional, losing his capacity to make sound decisions? It's a very worrisome, dangerous situation."
Putin's stability has been the cause of much speculation over the last month. Everything from his near-hour long rant in which he gave a revisionist history of Ukraine and Russia to photos of him sitting many metres away from his officials in meetings (possibly paranoid about COVID-19) has created alarm about the thinking of the man.
Former US Secretary of State Condoleezza Rice, who has met Putin numerous times, says this is no longer the usual cold and calculated Putin, but instead an "erratic man".
Graham Allison, a Havard political scientist who has worked to decommission nuclear weapons, told the New York Times that Putin's decision to put his forces on high alert made "no sense". He said this was "adding to the worry that Putin’s grasp on reality may be loosening".
But another international affairs expert, Stephen Walt, also told the Times that he didn't view it as Putin losing his mind as people should remember that "plenty of leaders that we regarded as fairly smart and fairly sensible did dumb things in the past".
Jim Clapper, the former US Director of National Intelligence, called the Russian leader "unhinged" and expressed "worry about his acuity and balance", something echoed by Kiwi politicians, including National's Christopher Luxon and the Greens' James Shaw.
Prime Minister Jacinda Ardern wouldn't comment directly on Putin's mental state, but referred to him as a "bully".
With Russia facing numerous logistical challenges in Ukraine and a stronger-than-expected Ukrainian resistance that has slowed down its advance and ability to take key objectives, US intelligence officials are also concerned Putin may begin lashing out even more indiscriminately and authorise further serious action.
"I do worry that he’s been backed into a corner. I do worry that there is no obvious exit ramp," US Senator Mark Warner, the chairman of the intelligence committee, said.
If Putin was to launch a nuclear strike, Welch said he wouldn't be aiming it at Ukraine as he doesn't want his troops fighting on a radiated battlefield.
Nuclear forces are usually "configured according to very detailed plans worked out in advance", he said.
"I would be stunned if there were a scenario that the Russian military planners have ever considered whereby Putin himself initiates the use of nuclear weapons when Russia is not actually under attack," he said.
"Russian doctrine is to use them only for self-defence. So they would actually have to jury rig some kind of scenario and make plans accordingly."
The idea of mutually-assured destruction (MAD), the thought that the use of nuclear weapons by two opposing sides would only lead to both being destroyed, has been the most significant deterrent to any country using their nuclear weapons.
Welch said we could instead see Putin stage a nuclear "demonstration" rather than leading with a "massive kind of nuclear assault that would trigger retaliation and result in the destruction not only of his country, but of civilisation".
"So it would be some kind of demonstration shot or a series of demonstration shots. I wouldn't want to be the Russian planner whose job it was to try to pick those," he said.
"I don't think I would want to pick capital cities in decapitation efforts because I would like to have senior leaders in other countries to talk to try, to negotiate a settlement down the road. So I imagine it would be something like targeting a naval base or an airfield, probably in Europe, I imagine, possibly in the United States.
"It would be a reckless act intended really only to signal a seriousness on Putin's part. And what does he follow up with? It's mystifying."
The United States doesn't have a "rule" where it would strike back with nuclear weapons in retaliation, but Welch said the doctrine is that you do retaliate to armed attacks. There are historical exceptions to that though, he said, such as Denmark's quick surrender to Germany during World War II.
"We've seen a lot of prudent restraint on the part of [US President Joe] Biden and other Western countries in the face of Putin's earlier nuclear alert," he said.
"They clearly didn't want to signal that they took it all that seriously or that they wanted to increase tensions in return. But the pressure to retaliate if there's actually a nuclear attack on some Western base would be very, very intense.
"It would be very curious to know what the conversation would be leading up to a decision, whether or not to retaliate and if so, how."
After Putin raised the alert, Biden was directly asked if Americans should be concerned about a nuclear war breaking out. He answered: "no". White House Press Secretary Jen Psaki later said the US had assessed Putin's order and "we see no reason to change our own alert levels".
Ukrainian Foreign Minister Dmytro Kuleba noted that Putin's nuclear forces order came just after Ukraine and Russia decided to meet for negotiations.
"We see this announcement this order, as an attempt to raise stakes and to put additional pressure on the Ukrainian delegation," he said.
It was still a "direct threat to us" and any nuclear attack would be a "catastrophe for the world", Kuleba said.
The UK Defence Secretary made similar comments, not recognising the terms Putin used when he made his order.
"We don’t see or recognise in the sort of phrase or the status [Putin] described as anything that is a change to what they have currently as their nuclear posture," Ben Wallace said.
"This is predominantly about Putin putting it on the table just to remind people, remind the world, that he has a deterrent."
According to Federation of American Scientists data, Russia and the US hold more than 90 percent of the world's nuclear warheads, with Russia having 5977 and the US having 5428.
