Modern warfare isn't just about the battle field and weapons. Its never been - propaganda has always matters, but its mattered more and more since Vietnam and war reporting being constant do to the rise of mass media. In this sense, wars don't happen in far away places like they used to and governments have to manage their home front and their war front well.
Since Putin started the invasion things haven't gone well for Putin on the Propaganda War.
His pretext to war was that Russia needed to go to war because there was a threat to Russians in the disputed regions of Ukraine. He started a panic, and told people to evacuate because they were at risk. These pictures were broadcast back to Russia. The Russian parliament were asked to vote to recognise these regions - the suggestion being that this would maybe bring peace. Of course, since Putin was intending to invade this was a pile of rot. But none the less many Russians (including at least two Duma MPs who have since publicly said they feel misled) believed this to be true.
What Putin really underestimated was quite how good the Ukranian propaganda and communication would be. The Ukranian President didn't buckle and run away from the intimidation of the invasion. He stayed and has unifyed his people and managed to rally support around him. The resistance on the ground produced a lot of images which don't look good for Putin.
Instead of there being a resounding swift victory, there were images of broken down tanks and rather inept Russian soliders. This makes Putin as a military leader look weak.
His next response has been to shut down twitter, facebook and youtube in Russia. This isn't what many expected. There was a fear that instead Western social media would be filled with gloating Russians saying how strong they were and how the West were to blame etc etc. And this would scare the West and deter them from getting involved because their voters didn't want to get involved in a war far away from home.
Instead, the images have horrified the world and the Ukranian President has inspired strength and support.
Remember the war was about regaining Putin in particular an image of being in control and being strong - covid has been a blow to Russia and there have been increasing rumblings about Putin himself with small, but growing protests at his rule. He had felt as if Russia had been slighted and wasn't respected and he had an agenda about rebuilding the glory of the Soviet Sphere of influence under the Russian Flag.
So he's been a bit pissed at how things have gone before and he's facing growing questions about his leadership. The decision over SWIFT and sanctions have gone further than pretty much in the west thought possible, so it's very likely to have caught Putin off guard too. He hadn't planned for the eventuality.
Tomorrow its likely there will be a big run on the Russian banks as it kicks in and Russians suddenly realise this isn't a 'special operation' (the word war has been banned) and its not far away and is going to effect them badly. The war has been brought to their door so now Putin has to justify it.
So the address about nukes:
There are two audiences here - the Russian domestic audience and the International one.
Putin has two key things he needs to get across - a position of strength to counter the damage to his strongman reputation thats occurred and to try and fracture the western alliance and support for Ukraine via threats and intimidation.
He wants to frighten and concern western public - in order to try and get them to undermine support from their governments for supporting Ukraine. Talking about nukes is frightening. Its supposed to be. Its supposed to be fucking with your head. Its supposed to make you doubt that your country is doing the right thing. It does not mean he is definitely planning to use them. Its from a position of weakness in his military plans and his propaganda war so far. He's trying to control of the narrative back.
He also has to double down on the 'moral cause' of the pretext to the war. He has to play the victim, at risk from the West's aggression to justify the war, which is going to bring home a lot more body bags than he had imagined. Like Afghanistan, Iraq and Vietnam for the Americans, body bags going home upset normal Russians. He needs them to feel that they have no choice but to fight or support the war. So what better way to suggest you are being threatened than to ready the defensive nuclear units? Why would you do this if there's no threat? He's trying to rally his people in part to stave off the anger that the banking crisis will bring. Again this is coming from a position of weakness.
My point here is this isn't necessarily anything to do with an actual military threat of nukes.
This is probably more about the propaganda war and Putin's need for crisis management following the last few days of things not going as well as hoped and the danger of him being percieved as weak. Its the classic go on the offensive approach.
If you remember from the Iraq War and 'Comical Ali' as he became dubbed, this isn't necessarily dissimilar. Comical Ali went on TV saying there were no tanks near Baghdad to try and retain control of a rapidly degenerating situation, even as US forces were already within the city limits.
Dictators always must maintain the facade of control and being strong otherwise, they personally, are at risk of losing power.
This moment is a real moment of threat to Putin.
It is potentially a moment of great risk to Europe so we shouldn't automatically dismiss it, but we should certainly put it into clear context: this is a boss who has had a bad week and so is taking it out on his staff and blaming others inside and outside the company for his own fuckups. Whether he decides he ultimately want to liquidate the company just out of frustration and spite is a much bigger step to take and really not as likely.
He's trying to fuck with your head. Understand he's trying to manipulate and scare you.