MOSCOW – Russian President Vladimir Putin is fond of nuclear saber-rattling: On the eve of Russia’s full-scale invasion of Ukraine in February 2022, the Kremlin leader presided over the rehearsal of a nuclear strike, and his not-so-veiled nuclear threats have since kept US officials on edge.

This week, Putin once again rattled the arms-control world by revealing proposed changes to his country’s nuclear doctrine. In a meeting Wednesday of his Security Council, the president said Russia would revise the doctrine to potentially lower the bar for the use of nuclear weapons, adding that Moscow would regard an attack by a non-nuclear state that involved or was supported by a nuclear state as a “joint attack against the Russian Federation.”

Nuclear retaliation, Putin continued, could be considered “once we receive reliable information about a massive launch of air and space attack weapons and their crossing our state border. I mean strategic and tactical aircraft, cruise missiles, UAVs [unmanned aerial vehicles], hypersonic and other aircraft.”

In simple terms, Putin was delivering a warning to Washington and other backers of Ukraine. The revision to the doctrine comes as Ukraine (a non-nuclear weapons state since it gave up claims to nuclear weapons after the collapse of the USSR) presses the United States for long-range weapons that would allow it to strike deeper inside Russia.

The doctrinal revamp is clearly meant to make Western policymakers think twice as Ukrainian President Volodymyr Zelensky presents his “victory plan” to the Biden administration. By brandishing the big stick of Russia’s nuclear arsenal, Putin is implying that the potential costs of providing Ukraine that weaponry may be too high for the West.

So does Putin’s statement move the Doomsday Clock any closer to midnight? Wednesday’s announcement sparked robust discussion online, with arms-control experts trying parse Putin’s language about the thresholds for nuclear retaliation.

Pavel Podvig, an expert on Russian nuclear forces, wrote in a thread on X that there was “deliberate ambiguity” in the announcement, particularly around what doctrine defines as aggression against Russia.

“In the current version of Russia’s nuclear doctrine, there is no distinction between an aggression by nuclear- and non-nuclear-weapon state,” he wrote. “All you need is an aggression that threatens the existence of the state.”

 (CNN) …[+]