Two European countries. Two nuclear arsenals operated differently and one big question.
Would the United States use its nuclear weapons to defend Europe in the unpredictable era of Donald Trump?
No ally wants to confront the possibility of nuclear war, or the US turning its back on them.
But as fears grow that Trump is increasingly sympathetic to Russia, and moving away from old friends, European nations are now discussing how it would tackle the threat of a nuclear attack without America's assistance.
Countries are turning to France and the United Kingdom, the only two European nations with nuclear arsenals of their own, for a possible way forward.
France has around 300 nuclear warheads, developed entirely by the French.
Its military has the power to launch the warheads from submarines or use fighter jets and bombers to drop them from the sky.
The UK has about 250 nuclear warheads, but unlike France, it does not necessarily hold the key to its own nuclear arsenal.
Britain developed its nuclear weapons in collaboration with the US.
The UK can decide when and if to use them, but Britain needs technical and logistical support from the US to be able to operate them.
Lukasz Kulesa, director of proliferation and nuclear policy at the Royal United Services Institute, said challenges would arise for the UK if its nuclear cooperation with the US was to end.
"That would cause serious problems in a mid-to-long term perspective, especially when it comes to the access of ballistic missiles, which is where the big dependency is," Mr Kulesa told the ABC.
"But switching to a completely sovereign program, or any kind of other international cooperation, would be costly and very time consuming."
Former UK foreign secretary Sir David Manning has been leading calls for the UK to end its nuclear cooperation with the US.
"It really is necessary for Britain and France to work more closely together because if American reliability ever came into question, then Europe could be defenceless in the face of Russian aggression," Sir David said.
"The contribution by America must now be to some degree in doubt, not today or tomorrow, but over the next few years and certainly as Trump and people like him are in control in Washington."
France wants to extend its nuclear umbrella
The recent shift in the trans-Atlantic partnership has forced French President Emmanuel Macron to reignite discussions about sharing its nuclear arsenal with its European allies.
"Europe's future does not need to be decided in Washington or Moscow," Mr Macron said.
But while previous French leaders have hinted its allies may already fall under its nuclear umbrella, for the first time other European countries are asking for nuclear support.
Poland has announced it will look at gaining access to nuclear weapons as a deterrent against potential future Russian aggression.
Poland's Prime Minister Donald Tusk said his country "is talking seriously" with France about being protected by the French nuclear umbrella.
Germany's likely next chancellor, Friedrich Merz, said his country is ready to have discussions about nuclear safeguards but said Europe would need to look beyond France and Britain, because Mr Trump's America cannot be relied upon.
"In view of the threats to our freedom and peace on our continent, the rule for our defence now has to be, whatever it takes," he said.
"It is crucial that Europeans make the greatest possible efforts to ensure that we are at least capable of defending the European continent on our own."
Is Europe safe without American assistance?
The balance of power isn't exactly in France's favour.
Russia has more than 5,000 warheads, nearly 10 times the amount of Europe as a whole.
The US also has more than 5,000 warheads.
[graph]"If you just compare the numbers then of course the conclusion may be that it is not enough, especially when you compare it to the current position where you have to rely on the US and their capabilities," Mr Kulesa said.
"If the idea is to be able to credibly threaten unacceptable damage to the other side, then the French and UK potential may be enough."
If nuclear capabilities are shared, Mr Kulesa said France would still be the only one that can pull the trigger.
"The French leadership is very clear that they maintain independence and sovereignty when it comes to the decision to use nuclear weapons," he said.
"This decision would be made by the French President alone," Mr Kulesa said.
Germany has long resisted French plans for closer European military cooperation, particularly when it comes to nuclear weapons.
France offered to start discussions on sharing its nuclear arsenal with Germany back in 2007, but that request was denied by then-chancellor Angela Merkel.
Mr Kulesa said the shift in policy highlights how Mr Trump's return to the White House is impacting the relationship with America, which has ensured European security for decades.
"This is confirmation of the level of concern and the level of uncertainty that, unfortunately, the Trump administration has inserted into the transatlantic relationship," he said.
It was the 1960s when France's then-president Charles de Gaulle decided to make his nation's nuclear deterrent strategically independent from the United States, foreseeing a future when America's support might not be guaranteed.
In the era of Mr Trump, that decision might matter now more than ever.
