This sparked major fears that Russia had – deliberately or not – struck NATO territory, which could have brought all member states into the ongoing war.
Nato, the North Atlantic Treaty Organisation, is made up of 30 member states, who have all promised to support each other if they are attacked. Ukraine is not part of the alliance, but Poland is.
However, Nato has since said there is no sign this was “deliberate attack”, and that they believe it was an accident from Ukraine’s air defence system. An investigation into what happened is still underway.
So – what does this incident mean for the war overall and will there be any long-term impacts?
A recap of Tuesday’s events
On Tuesday, Russia ordered more than 90 missiles to fire at Ukraine, according to Kyiv, mostly aimed at the country’s energy supplies.
Ukraine claims 77 were shot down (along with 11 drones), but some hit Lviv which is close to the Polish border.
It happened while most of Ukraine’s allies were meeting in Bali at the G20 Summit – a conference Russian president Vladimir Putin had chosen not to go to, sending his foreign minister Sergei Lavrov in his place.
Then, a stray missile came down at Prezewodow, which is 4 miles from the border between Poland and Ukraine and two people were killed.
Poland initially claimed the missile was Russian made.
Russian spokesman Dmitry Peskov subsequently accused the West of acting hysterically, and alleged Poland should have made it clear the debris actually came from Ukraine’s S-300 air defences.
In the meantime, world leaders discussed how to respond if it appeared Russia had struck a member state of Nato.
Poland’s military was also placed on high alert in case further attacks came, while Western leaders at the G20 summit in Bali spoke out against Russia’s “barbaric missile attacks” on Ukraine, and reiterated their support for Poland.
Ukraine’s foreign minister Dmytro Kuleba also said any suggestion that Ukraine was responsible for the attack was a Russian “conspiracy theory”.
Leaders soon tried to dispel tensions
US president Joe Biden said soon after the explosion that it didn’t look like the missile came from Russia, due to its “trajectory” and that nothing could be confirmed until the investigation.
Leaders from Nato were also quick on Wednesday morning to de-escalate the situation, by claiming that there was no evidence the missile (likely Russian-made) had been fired from the Russian side.
Once Polish president Andrzej Duda clarified there are no signs that the attack was intentional, Jens Stoltenberg, the secretary-general of Nato, repeated the message in a press conference.
He added that there was no sign Russia was preparing offensive actions against Nato either.
He said an investigation is still ongoing, by preliminary analysis suggested the explosion came from “Ukrainian air defence missiles figures to defend Ukrainian territory against Russia cruise missile attacks”.
Stoltenberg also cleared Ukraine of any blame. He said: “Let me be clear, this is not Ukraine’s fault. Russia bears ultimate responsibility as it continues its illegal war against Ukraine.”
Ukraine does stock both Soviet and Russian-made weaponry, and has also seized additional Russian weapons during its counteroffensive.
How was Russia responded?
The Kremlin repeatedly it has nothing to do with the deaths.
A spokesman for the country’s defence ministry told Russia’s state owned news that its strikes were 22 miles from the Polish border, and claimed photos of the site showed a Ukrainian S-300 missile.
They did also tell the BBC: “It’s worth noting the restrained and much more professional reaction of the American side and the American president.”
The former Russian president Dmitry Medvedev also said on Wednesday that the moment was a sign the West was moving closer to another World War.
He tweeted: “The incident with the Ukrainian-alleged ‘missile strike’ on a Polish farm proves just one thing: waging a hybrid war against Russia, the West moves closer to world war.”
It remains unclear what Russia will do next in the war, having just withdrawn from the only regional city it had captured since the invasion began, Kherson, although the missile strikes suggest it will continue with its air strike offences.
But now the West is keeping a watchful eye
Nato is keen not to be directly involved in the conflict, so it’s unlikely any direct escalation will happen off the back of the stray missile.
Speaking on Wednesday, Stoltenberg said he had spoken to Polish president Duda and the military alliance would continue “monitoring” what happened.
But, he was keen to emphasise that the West was still watching.
“I think this demonstrates the dangers connected to the ongoing war in Ukraine, but it has not since changed our fundamental assessment of the threat against the NATO allies.
“It shows the importance of monitoring or being vigilant of the presence,” he said – but he added that Nato has increased the capacity of its air defence systems.
What about ‘Article 5’?
This a pledge of mutual defence among all member states, meaning if one is attacked, they all respond to assist their ally.
This would not only increase global military tensions, but raise the risk of a nuclear standoff between the US and Russia.
But, Poland has also suggested it may not trigger the alliance’s Article 5 now it is clear the missile did not come from Russia, another sign that tensions are de-escalating.
Defences are up
However, Lithuania wants Nato’s air space to be defended, and said it would be prepared to deploy air defences on the Polish border with Ukraine.
A German spokesperson said it would support that too, but pointed out that all Nato allies had agreed to avoid further escalation.
Meanwhile, Italy’s PM Giorgia Meloni echoed Stoltenberg’s claims about Russia’s culpability. She said: “The possibility that the missile falling on Poland was not a Russian missile but a Ukrainian one changes very little.”
UN secretary-general Antonio Guterres said he was “very concerned” about the explosion, and called for an investigation, too.
What will Ukraine do?
Kyiv is yet to weigh in since it has emerged the missile did not come from Russia, although it sent its condolences to Poland last night and was quick to blame Russia.
The country has since said it wants “immediate access” to the explosion site, and is calling to see the information which led the West to conclude it was likely a Ukrainian missile.