The world was on a knife edge today as leaders from Nato countries discussed what to do after a missile of unconfirmed origin landed in a Polish border town, killing two people.
Initial media reports referencing an unnamed senior US intelligence official and the Ukrainian government pointed the finger at Russia. But later US President Joe Biden said the blast may not have been caused by a missile from Russia.
Speaking after a meeting of leaders of NATO states at the G20 Summit in Bali today, Biden said there was "plenty of evidence to contest" the idea the missile was fired from Russia, given the trajectory. He said it was too early to state conclusively.
According to US officials, initial findings suggested that the missile was fired by Ukrainian forces at an incoming Russian missile, the Associated Press said.
Poland, a NATO member, has launched an investigation and is considering whether to invoke elements of Nato's collective defence treaty, which regards an attack on one of its members as an attack on all.
So what could happen next?
University of Waikato international law Professor Al Gillespie told Checkpoint the incident presented as "the nightmare scenario", but that it was reassuring all 30 NATO countries had to agree unanimously on their response.
"Because some NATO countries may be more provocative than others, but trying to get all 30 of them to agree that you need to consider it a collective defence is going to be difficult, especially if there's uncertainty where this missile came from."
The worst-case scenario would result in the Ukraine-Russia conflict spilling over into NATO countries where it would become "uncontrollable".
Listen to the full interview
Lesser options in response to what has happened could include providing Poland with more air defence, stationing more NATO troops closer to the border with Russia and sending more weapons to Ukraine.
Before NATO members tried to reach consensus on any response, Poland would need to make a request to NATO, saying its territorial integrity or security had been threatened.
"They start the ball rolling," he said.
Police secure the entrance to the Polish town of Przewodow where at least two people have been killed by a stray missile. Photo: AFP
A cornerstone of the NATO treaty is Article 5, which stipulates that the parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all, Reuters reported.
There has been much discussion of the article in the wake of the incident.
Gillespie said to trigger Article 5 the action had to be an intentional armed attack - it could not be accidental, reckless or negligent.
"If there's an accident, best case scenario the country that did it ... would admit it, apologise and offer compensation to the Polish people who have suffered."
Adding to the current tension was Russia's response to the accusation it was responsible - it has labelled the claim a provocation, designed to escalate the war.
Gillespie said the world was in "a fog of war situation" and people should be sceptical of all information.
"One thing I would suggest though is that they would know where it came from because you can look at the munition itself, but also the tracking devices right now, you can see where the missile moved through the air space, so someone will know where it came from."
Even with hypersonic missiles it was possible to detect where they had been launched from, where they were going and where they would impact so that air defence systems could intercept them.
Biden's statement mentioning the missile's trajectory should lessen the tension, he added.
BBC correspondent Jonathan Head told Checkpoint leaders were being extremely cautious about the response to the Polish missile incident, lest they bring the prospects of a nuclear war closer, or further a new cold war.
"I think that they're still very unclear about who fired the missile where it came from, so nobody's going to start talking about what response is relevant until they've got a lot more information," he said.
"And I think that will take some time...
"President Biden has been on the phone to the Polish Prime Minister, but they're not giving anything away at this stage. And I think that's understandable, even the Polish authorities are not yet sure exactly what the source of this missile is."