Ukraine war drives shift in Russian nuclear thinking - study

LONDON, Jan 22 (Reuters) - The war in Ukraine has dented Russia's confidence in its conventional forces and increased the importance to Moscow of non-strategic nuclear weapons (NSNWs) as a means of deterring and defeating NATO in a potential future conflict, a leading Western think-tank said on Monday.

NSNWs include all nuclear weapons with a range of up to 5,500 km (3,400 miles), starting with tactical arms designed for use on the battlefield - as opposed to longer-range strategic nuclear weapons that Russia or the U.S. could use to strike each other's homeland.

Monday's report by the International Institute for Strategic Studies (IISS) raised the question of whether Russia might be emboldened to fire a NSNW in the belief that the West lacks the resolve to deliver a nuclear response.

"The Russian perception of the lack of credible Western will to use nuclear weapons or to accept casualties in conflict further reinforces Russia's aggressive NSNW thought and doctrine," it said.

It said the logic of using a NSNW would be to escalate a conflict in a controlled fashion, "either to prevent the US and NATO from engaging, or to coerce them into war termination on Russian terms".

Moscow denies wielding nuclear threats but several of President Vladimir Putin's statements since the onset of the war in Ukraine have been interpreted as such in the West - starting on day one of the Russian invasion when he warned of "consequences that you have never faced in your history" for anyone who tried to hinder or threaten Russia.

His warnings, however, have not prevented the U.S. and its NATO allies from providing massive military aid to Ukraine including advanced weapons systems that were unthinkable at the start of the war.

Putin has resisted hawkish calls to alter Russia's stated doctrine, which allows for nuclear use in the event of "aggression against the Russian Federation with conventional weapons when the very existence of the state is threatened". But he has shifted Russia's stance on key nuclear treaties and said he is deploying tactical nuclear weapons in Belarus.

Western analysts and policymakers have been closely tracking a debate among Russian military experts about whether Moscow should lower its threshold for nuclear use.

Last year, for example, Russian analyst Sergei Karaganov spoke of the need to threaten nuclear strikes in Europe in order to intimidate and "sober up" Moscow's enemies.

William Alberque, author of the IISS report, said Karaganov was part of a wider discussion in Russia on the failure of its military to win the Ukraine war decisively and quickly.

"They're afraid, according to their own debates, that that has further emboldened us, so that's why this nuclear debate is happening now, where they think 'we need to do something else to super-scare the United States'."

He told reporters that Western intelligence would be able to pick up a number of signals if Russia was actually preparing to launch a NSNW.

These would include the movement of weapons from a central storage facility to an air base, and possibly conventional strikes near the planned target area in order to cripple radar and anti-missile defences.

Putin at that point would probably move to a nuclear shelter and put Russia's entire nuclear command and control system on high alert in case of a major nuclear response by the United States, he said.

Alberque said any Russian use of NSNW would require Moscow to calculate the right "dose" to coerce its adversaries to back down rather than triggering a cycle of escalation.

The question of how to respond to such a scenario is what "keeps U.S. planners awake all night", said Alberque, who has previously worked at the Pentagon and NATO.

"Once the other side crosses the nuclear threshold, how do you prevent the logic of escalation, escalation, escalation to annihilation? How do you contain it, how do you keep it down? This is one of the hardest problems, this is a problem that has existed since the dawn of the nuclear age."