Thanks to imbecilic comments by President Biden, the threat of nuclear war just got a lot more serious if new reports are to be believed.  The estimable David Goldman (AKA Spengler), writing with Uwe Parpart, warns us:

What does Vladimir Putin have to do to convince Washington that the Ukraine crisis is a preliminary skirmish in what might be a nuclear war? On February 23, Putin warned of nuclear war. On February 19, he conducted a full-dress drill of Russian ballistic missile forces. On February 27, he put Russia on a nuclear alert — which remains in effect.

Joe Biden didn't get the message.

Then on March 29, Moscow sent a red-alarm signal to the West by leaking news that "Putin and his high command have decamped to secret bunkers, following a Kremlin statement that Russia would use nuclear weapons to counter an 'existential threat,'" the Daily Mail reported, citing investigations by journalist Christo Grozev.

That Daily Mail article claims:

New evidence has emerged Vladimir Putin and his highest ranking commanders are running the war in Ukraine from top secret nuclear bunkers. 

Movements of planes used by top Kremlin officials show Putin may be in a hideaway near Surgut, in western Siberia, it has been claimed.

His defence minister Sergei Shoigu - who has been mysteriously absent for several weeks, sparking rumours about his health - is believed to be in a bunker near Ufa in the Urals, 725 miles east of Moscow, according to investigative journalist Christo Grozev. (snip)

The suspected use of the high security nuclear bunkers is concerning as it leads to suggestions Putin may be prepared to deploy nuclear weapons, a move that would lead to inevitable reprisals.

Putin and defense minister Sergei Shoigu at the 2019 Victory Day Parade.
Kremlin.ru via UKDM.

Biden foolishly called for regime change with the now infamous 9 words, "for God's sake, this man [Putin] cannot remain in power."  From the standpoint of Vladimir Putin, that is an existential threat.  Having been branded a war criminal, and watching the seizure of assets of Russian oligarchs, there is no graceful retirement to the French Riviera like some deposed murderous third-world oligarch.  If Russian forces are doing as badly as our media claim, then Putin may well feel cornered.  Gaddafi rode a bayonet at the end, and Ceaușescu was executed by a firing squad.  Vlad has no intention of hiding in a spider hole like Saddam until found and hanged.

Biden's word is worthless in Putin's mind.  He claims he didn't say what he clearly said when questioned about regime change.

A man in this situation, whether sane or not, might well conclude that nuclear war is the preferable option.