BY BRENDAN COLE ON 4/21/22 AT 1:01 PM EDT
Russia has carried out its first successful test of a nuclear-capable intercontinental ballistic missile (ICBM), which Vladimir Putin said would make adversaries “think twice.” What world leaders might be thinking about even more is whether the Russian president could resort to such weapons during his invasion of Ukraine.
The launch of the Sarmat missile on Wednesday from the northwestern Arkhangelsk region comes in a week of mixed messaging from Russia in which its foreign minister Sergei Lavrov told an interviewer with India Today it would use, in Ukraine, “conventional weapons only.”
The U.S. said it was notified beforehand about the ICBM test, a requirement under the New START weapons treaty between Moscow and Washington. While Pentagon spokesman John Kirby said the test did not pose a threat, its timing is a signal from Putin, who put his strategic nuclear weapons forces on high alert at the start of his invasion.
“The nature of a conflict which involves both Russia and NATO, even indirectly, is that there is bound to be a nuclear shadow over it,” said Malcolm Chalmers, deputy director‑general of the Royal United Services Institute (RUSI) think tank in London. “That does not mean that the use of nuclear weapons is imminent or even likely. “
Chalmers said that there was similar nuclear signaling from Russia after it seized Crimea in 2014 with the aim of deterring direct NATO and U.S. involvement.
“The primary nuclear problem we could see in the coming period would be in a situation where Russia feels increasingly frustrated by its ability to achieve its objectives by the use of conventional force,” he told Newsweek.
Russia’s invasion has stalled and its troops have retreated from the Kyiv region, hit by a high loss of troops and equipment. The Kremlin has been focusing its latest offensive on eastern Ukraine with the aim of seizing the Donbas region.
Chalmers said that using nuclear weapons would be a “tremendous gamble” for Russia, but other factors might combine to push Putin towards the drastic move if he felt Russia’s red lines had been crossed, and that his own conventional options had been exhausted.
These could include the perception that NATO forces are getting more directly involved in the conflict—for instance if drones used in Ukraine were being operated by alliance forces in NATO territory.
Another nuclear risk factor could be “if Russia felt its own territory was under threat,” including Crimea.
“If the battle for Donbas ends in a stalemate, or Russia has in some sense lost that battle and President Putin’s conventional options narrow, will there be circumstances in which he wants to wave a nuclear card, or make a credible nuclear threat to force Ukraine or indeed NATO to back off?” Chalmers said.
In 2020, researchers at Princeton’s Program on Science and Global Security published an analysis of what might happen if Russian or NATO leaders used nuclear weapons first in a conflict in Europe.
Initial “tactical” nuclear detonations could escalate into a an exchange of thermonuclear weapons involving Russia’s arsenal of 1,450 strategic warheads and the U.S. arsenal of 1,350 strategic warheads on its missiles and bombers.
In such a scenario, more than 91 million people were projected to die in just the first few hours. Millions more would die from exposure to radiation in the following years during which health, financial, and economic systems would collapse.
“The danger of nuclear weapons arises if the war were to widen outside of Ukraine,” retired Lt. Col. Bill Astore, ex-professor of history at the U.S. Air Force Academy (USAF) told Newsweek.
“For example, if NATO enforced a no-fly zone and started shooting down Russian planes, I could see Putin responding with a tactical nuclear strike against a NATO airbase.
“That would risk a wider nuclear war, truly a horrifying scenario, which is why those who are calling for NATO escalation and direct involvement in the war are being irresponsible.”
Lavrov’s comments this week echo those made by Kremlin spokesman Dmitry Peskov who told PBS in March “no one is thinking about” using a nuclear weapon. However, Peskov was responding to a question about ex-President Dmitry Medvedev who had listed scenarios in which Russia reserves the right to use nuclear weapons.
“We should never believe what the Kremlin or Sergei Lavrov says at face value, but it is positive that they are ruling out the use of nuclear weapons in the assault on Ukraine,” said Daryl Kimball, executive director of the Arms Control Association who said such a prospect is “theoretically there but I think it is unlikely.”
However, the longer the conflict continues means that the heightened risk of a direct NATO-Russia encounter “will persist for many weeks, if not months.”
“It is not like the  Cuban missile crisis,” Kimball told Newsweek, referring to the brinkmanship between the USSR and the U.S. “Back then the risk of nuclear use was high—but the crisis lasted 13 days.
“This crisis has lasted well over 13 days. Unlike then when there was no direct shooting we now have a hot conflict that can easily escalate.
“The risk of nuclear use is higher than it has been since the end of the Cold War and it is going to last for some time to come,” he said.
“As Putin might become more desperate, as the war drags on and as his political position becomes more tenuous, he could once again resort to nuclear threat making and we could have the potential for miscalculation.”
Alan Cafruny, professor of international affairs at Hamilton College in Clinton, New York said the use of nuclear weapons “is unlikely but not impossible,” and of concern is the escalatory pressure from U.S. politicians calling for further NATO involvement.
“Especially in the context of domestic volatility in the United States and continuing setbacks for Russian forces, mistakes and misperceptions are certainly possible,” he told Newsweek.
Kremlin officials told Bloomberg this week they are becoming “increasingly” worried Putin could use limited nuclear weapons. Meanwhile, CIA director William Burns said Putin could use a tactical or low-yield nuclear weapon out of “potential desperation,” although there was no evidence such an attack was imminent,according to The New York Times.
Abby Schrader, history professor at Franklin & Marshall College in Pennsylvania said that the latest ICBM test was not necessarily an indicator of Putin’s intentions in Ukraine and was “macho saber rattling more than a real threat.”
“Much more concerning to me is that Putin could well resort to the use of tactical nuclear weapons,” she told Newsweek. “Old-school, low-yield nukes, with short-range delivery systems, similar to those dropped by the U.S. on Hiroshima and Nagasaki.”
“He would deploy these to dramatically take out limited targets while stopping short of provoking, as the old Cold War doctrine put it, ‘mutually assured destruction.'”
Newsweek has contacted the Ukrainian Defense Ministry.