Denmark is used to the cold, but this winter has been different.
The capital, Copenhagen, is thawing from its most frigid January in 16 years, but the geopolitical climate is turning frostier.
US President Donald Trump's threats to seize Greenland have left Danes feeling the chill from a once-staunch NATO ally.
"This sense of betrayal is really out in the open now," says former chief analyst of the Danish Defence Intelligence Service, Jacob Kaarsbo.
"There's a sense of a stab in the back."
The US president has since walked back talk of military action to take Greenland, but Jacob warns the issue is "far from over".
"The trouble is Donald Trump is not going to get what he wants" from the current diplomatic process, he tells Foreign Correspondent.
Last month, Trump said he had struck a "framework" deal with NATO Secretary General Mark Rutte, who later clarified the talks were about security, not sovereignty.
Denmark is still in discussions with Trump administration officials, but has repeatedly said US ownership of Greenland is not on the table.
"[Trump] wants control over Greenland and he's not going to get it," Mr Kaarsbo said.
"We'll just have to see what he does then, because he'll have the next move. Will that be to threaten militarily again? We don't know. So we have to be prepared."
Mr Kaarsbo fears the country faces the greatest threat to its sovereignty since the Second World War.
Denmark finds itself exposed on two fronts — from an old foe, Russia, and an old ally in the United States.
"America is a formal ally because NATO still exists, but that's on paper. In reality, it's not an ally. It's not someone we can depend on," Mr Kaarsbo said.
"[Denmark is] in a precarious position and we are under pressure both from the east and the west, and we have to handle it."
Denmark's dangerous neighbourhood
Even before the US started threatening Denmark's most westerly territory in January, Danes were on edge.
Countries across the Baltic Sea region have been on high alert over a growing threat in the east, Russia.
NATO has long suspected Russia's ambitions go beyond Ukraine, with Mr Rutte warning it could attack a NATO country within five years.
"We are Russia's next target, and we are already in harm's way," Mr Rutte said in December.
"We must be prepared for the scale of war our grandparents or great-grandparents endured."
Those fears have been stoked by a Russian campaign to covertly menace its neighbours across the region.
Russia is accused of launching "hybrid" or "grey zone" warfare, where a hostile state carries out indirect attacks designed to intimidate, sow panic and disrupt daily life.
Denmark has been a target, suffering a spate of drone incursions and cyber attacks.
In September, drones were detected in the skies around six airports, including Copenhagen's main airport, forcing three to shut down.
"This is the most serious attack on Danish critical infrastructure to date," Prime Minister Mette Frederiksen said at the time.
While Russian President Vladimir Putin has been coy about claiming responsibility for the hybrid attacks, Ms Frederiksen has little doubt who is behind them.
"It must be clear now to everyone — Russia will not stop until they are forced to do so," she told a gathering of European leaders last October.
There is a view in Denmark that Russia's shadowy campaign is a form of payback for the country's leading role in supporting and financing Ukraine.
There are also fears these attacks could be merely a prelude to more open hostility, even invasion.
The other island worrying Denmark
That scenario would likely play out on Bornholm, an island in the heart of the Baltic Sea on Denmark's most easterly flank.
Bornholm is one of the closest pieces of Danish territory to Russia.
Surrounded by rocky coastlines and beautiful beaches, locals call the popular tourist destination "sunshine island".
But it has a darker history.
At the end of World War II, Bornholm was under Russian occupation for nearly a year before being handed back to Denmark.
Now some of its residents, including the curator of the local museum Jakob Seerup, fear history could be about to repeat itself.
As things stand, Mr Seerup said it would be "all too easy" for Russia to occupy Bornholm again.
"Bornholm could be seized in a night by a contingent of Russian soldiers. That sounds like some wild Tom Clancy novel, but it is actually within the realm of possibilities," he said.
The island also sits just 350 kilometres from Kaliningrad, a Russian exclave between Poland and Lithuania, and one of the most militarised places in Europe.
It is home to Russian warships and long-range missiles.
Mr Seerup believes those missiles could easily reach Bornholm.
"We know they have deployed fighter bombers that can launch Iskander missiles, like nuclear-capable missiles," he said.
Denmark is so worried Russia could attack Bornholm that it is stationing a permanent battalion of troops on the island for the first time in decades.
[IMAGE Bornholm map]It is part of a wider military build-up now taking place across the country.
Prime Minister Mette Frederiksen has declared Denmark must "re-arm massively" as it muscles up to Russia.
There is a sense of urgency in the process.
Denmark has expanded its mandatory conscription program to include women for the first time and nearly tripled the length of its mandatory military service from four to 11 months.
"I think everyone would like to have no war, but that might not be the reality," the head of conscription for the Danish Army, Colonel Kenneth Strøm, told Foreign Correspondent.
"[Conscripting women] is obviously to have enough boots on the ground. We need all the best young men and women in the armed forces."
The recruitment drive aims to grow Denmark's reserve army from about 5,000 annual conscripts to about 7,500 by 2033.
Denmark is ramping up its military spending too.
The national defence budget has grown to almost $23 billion as the country invests in more F-35 jets, long-range missiles, drones and ships.
Denmark's falling out with the US over Greenland has left it all the more exposed to Russia, says intelligence analyst Jacob Kaarsbo, by exposing deep divisions between the US and Europe.
"I'm sure Putin would be delighted with what he's seeing, this whole rupture of NATO and rupture between Europe and the US," Mr Kaarsbo said.
It's "what the Kremlin has been striving for for many years".
A pivotal moment for NATO
For now, Greenland has been a "wake-up call" and "a pivotal turning point" for NATO members like Denmark, Mr Kaarsbo said.
He warns that US threats to invade an ally is "likely the end of NATO as we know it" and that Europe must now forge a military alliance that does not rely on the US.
"The issue of Greenland was really so fundamental," he said.
"I think there's much more of a realisation now that the Europeans have to take care of European security on their own, and then we'll see what the US does."
He said that would involve ramping up Europe's defence industrial base to become less reliant on US weapons and developing a command structure that can function independently.
Greenland has also exposed the failure of a more compliant approach to diplomacy with the US president, Mr Kaarsbo said, with European leaders already taking a harder line.
"They see this whole idea of treating Trump as a 'royal highness' doesn't work because the pressure will continue," he said.
"The question Europeans should ask themselves is how do we stand up to Russia without the US? Because we can't rely on a partner that is unreliable, so we need to figure it out."
With threats to the east and the west, it is a question Denmark is now racing to answer.
Watch NATO Under Attack tonight on Foreign Correspondent at 8pm on ABC TV, ABC iview and YouTube.
