Russian President Vladimir Putin has set a "red line" for the U.S. and its allies, indicating that Moscow may consider a nuclear response if they permit Ukraine to launch strikes deep into Russian territory using long-range Western missiles.
This prompts a crucial question for the West: is he serious about this threat?
This inquiry is crucial for the future of the conflict. If Putin is merely bluffing, as Ukraine and some of its backers suspect, the West might feel emboldened to enhance its military support for Kyiv despite Moscow's warnings.
Conversely, if he is serious, there is a significant risk—repeatedly emphasized by Moscow and acknowledged by Washington—that the conflict could escalate into World War Three.
In his latest warning, Putin on Wednesday broadened the scenarios under which Russia might resort to nuclear weapons.
He mentioned that such a response could occur in reaction to a significant cross-border conventional assault involving aircraft, missiles, or drones. He stated that a rival nuclear power backing a nation attacking Russia would also be deemed complicit in that attack.
Both conditions directly apply to the situation that would emerge if the West allows Ukraine to strike deep into Russian territory using Western long-range missiles like the U.S. ATACMS and British Storm Shadows, which Putin claims would require support from Western satellites and targeting systems.
"It was a very clear message: 'Don't make a mistake — all these kind of things may mean nuclear war,'" said Nikolai Sokov, a former Soviet and Russian diplomat.
Bahram Ghiassee, a London-based nuclear analyst at the Henry Jackson Society think-tank, linked the timing of Putin's remarks to Ukraine's lobbying of the West for long-range missiles and the fact that President Volodymyr Zelenskiy is making his case to US President Joe Biden this week.
"Putin is saying: just stop it right there," Ghiassee said.
Reaction from Kyiv was swift, with Zelenskiy's chief of staff accusing Putin of "nuclear blackmail".
"In my opinion, this is yet another bluff and demonstration of Putin's weakness. He will not dare to use nuclear weapons because that will make him a complete outcast," Anton Gerashchenko, a former adviser to Ukraine's internal affairs minister, said on X.
