That’s according to the updated nuclear deterrence concept.
Russian President Vladimir Putin has changed the terms of use of nuclear weapons.
The updated concept of nuclear deterrence says nukes can be used even if Russian targets are under threat of conventional weapons of the country’s adversaries.
The use of nuclear weapons is still recognized as a “last resort” measure, seen solely as a “deterrent”.
However, among the conditions of possible use, there are cases of aggression where conventional weapons target Russia’s critical objects.
In its nuclear deterrence efforts, Russia will look into the deployment by potential adversaries of hypersonic and laser weapons, missiles, and strike drones.
(c) Unian

“The updated concept of nuclear deterrence says nukes can be used even if Russian targets are under threat of conventional weapons of the country’s adversaries.”
Might as well just sign your death certificate then, one nuke let loose by the psycopath will see Russia disappear forever.
And it’s not even an attack or invasion, it’s just the “threat” of a conventional weapon.
So if Ukraine shoots at a Moskali tug boat off the coast of Odesa, Lilly-Put-In can nuke Kyiv…
Moskali are getting shot every day in Northern Africa and the Donbas but he’s not nuking
That’s because the Nukes are the only things they have that work……..Or did work.