The Kremlin has resorted to nuclear exercises and threats to intimidate the West, relying on a widespread notion that fear of nuclear warfare could pave the way for a victory against Ukraine. It's too dangerous for the US to take the bluff right now, especially as America has failed to ramp up its nuclear deterrence and Putin has shown his willingness to accept great casualties as he pursues expansionist goals.
It's a matter of fact that Moscow has never intended to deploy nuclear weapons — the Kremlin has been left with few available options, as the US openly threatens Russia with a real war by stationing its nuclear arsenal in Europe and training NATO allies in using such weapons. Amid these exercises, Russia is merely seeking to enhance its readiness in the event of a nuclear attack from the West.