Russian President Vladimir Putin's order to heighten the alert status of his nuclear forces has raised fears in the U.S. that the war in Ukraine could lead to a devastating miscalculation, as well as spurred debate over the United States' own nuclear policies.
As of Monday morning, U.S. officials said they had seen no sign that Putin's order has been followed by significant changes in the Russian nuclear posture.
But officials and nuclear nonproliferation advocates alike are still warning that Putin's announcement is a dangerous escalation in the war he started last week in Ukraine.
"It's my judgment that Putin's publicly announced statement that he was raising the alert levels yesterday was designed more to reinforce his earlier threats against those who might seek to intervene in his invasion against Ukraine from doing so, rather than to actually raise the alert levels to the point where they might actually be used," Daryl Kimball, executive director of the Arms Control Association, told Military.com in a phone interview.
"Nonetheless, it's an extremely irresponsible and risky move that I think increases the risk of miscalculation and an escalation," Kimball added.
In a televised statement Sunday, Putin ordered his military leadership to put nuclear deterrent forces on a "special regime of combat duty" in response to "aggressive statements" from the West and escalating sanctions that are increasingly choking off Russia's economy.
"I order the minister of defense and the chief of the general staff to transfer the deterrence forces of the Russian army to a special mode of combat duty," Putin said in a meeting with Defense Minister Sergey Shoigu and Chief of the General Staff Valery Gerasimov.
But Putin's phrasing has confounded analysts, with a senior U.S. defense official telling reporters Monday the Pentagon is still working to decipher exactly what he meant.
"It's not a term of art in what we understand to be Russian doctrine," the official said. "So that's why we're still analyzing it and reviewing it to try to understand what exactly it means."
The announcement, which came amid what western officials have described as Russian frustration at stronger-than-expected Ukrainian resistance and Moscow's own military logistics failures, was widely interpreted as putting Russian nuclear forces on high alert.
Following Putin's order, the Russian Defence Ministry reported that more troops have been added to the command posts of all of Russia's nuclear forces, according to The Associated Press.
In the meantime, the United States has seen no major movements following Putin's statement.
"I don't believe we've seen anything specific as a result of the direction that he gave, at least not yet, in terms of appreciable or noticeable muscle movements," the senior defense official told reporters.
Asked Monday whether Americans should be worried about nuclear war, President Joe Biden responded simply, "No."
Russian strategic forces are always on alert, making it unclear what has fundamentally changed, said Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists.
"The core of the announcement is saber-rattling to scare the West and get some concessions," Kristensen told Military.com in a phone interview.
Should Russia move its mobile long-range nuclear missiles out of their bases and hide them around the country, send out significantly more ballistic missile submarines than normal or increase the activities of its bomber fleet, that would signal that Putin's announcement was more than rhetorical, Kristensen added.
While it is unclear what concrete actions Russia will take now, Putin's announcement appears unprecedented in the post-Cold War era, with experts pointing to the U.S. military raising its alert level in 1973 during the Yom Kippur War as the most recent historical comparison.
Amid the current crisis, the Biden administration has not raised the U.S. military's alert status, with the senior defense official saying that "we remained comfortable and confident in our own strategic deterrence posture."
That stance has earned praise from arms control advocates who say it is the right move to avoid further raising temperatures unnecessarily.
"To their credit, the United States has not responded in kind," Kristensen said. "On the contrary, DoD [Department of Defense] has been very, very cool-headed and clear. ... They don't have to take the bait."
The Cold War-style nuclear escalation over Ukraine comes as the United States is reviewing its own nuclear policies.
The Biden administration has been working on a Nuclear Posture Review, a formal document outlining American nuclear policy drafted by each new administration, that has been expected to impose at least some limits on the U.S. nuclear arsenal, including possibly canceling Trump administration plans for a sea-launched cruise missile or changing U.S. policy to declare the "sole purpose" of nuclear weapons is deterrence.
Republicans who were already critical of any plans to curtail U.S. nuclear might have seized on Putin's announcement Sunday to bolster their arguments.
"Reports that Putin has placed Russia's nuclear forces on higher alert is a stark reminder of why we need a strong, effective deterrent to meet the growing threats facing the U.S. and our allies," Senate Armed Services Committee ranking member Jim Inhofe, R-Okla., tweeted Sunday. "The upcoming Nuclear Posture Review cannot ignore this reality."
But arms control advocates say the dangers of the current situation show more restraint is needed in nuclear policy.
"We do not want to commit the same egregious fouls that Vladimir Putin is committing here, including threatening the first use of nuclear weapons in the conflict," Kimball said.
Russian military doctrine calls for using nuclear weapons only when the existence of the state is at risk.
Still, with Moscow's invasion of Ukraine going worse than it expected, Russia hawks in Congress are warning that a desperate Putin could pull the trigger.
"Now the economy is in shambles & the military is being humiliated & his only tools to reestablish power balance with the West is cyber & nukes," Sen. Marco Rubio, R-Fla., the ranking member of the Senate Intelligence Committee, tweeted Monday.
Experts also warn that Russian nuclear doctrine is vague enough that Putin could respond to a nonnuclear threat to his rule -- such as sanctions cratering the Russian economy -- with a nuclear answer.
"There are some scenarios in which you can imagine, not just this invasion of Ukraine, but some scenarios in which he might seriously consider so-called limited use in a conflict that threatens the existence of the Russian state," Kimball said, "which he, of course, probably interprets as him."
-- Rebecca Kheel can be reached at firstname.lastname@example.org. Follow her on Twitter @reporterkheel.