Russia’s invasion of Ukraine, which began on Thursday, is the biggest attack on a European country since the Second World War.
At the centre of the massive offensive is Ukraine’s capital Kyiv – home to three million people, with many fleeing the city.
Sky News talks to Professor Michael Clarke, former director general of the Royal United Services Institute (RUSI) and security analyst, who offers his assessment of the current situation.
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How is the battle for Kyiv playing out?
Russian forces operate in a similar way to our own forces.
They precede their attacks with air support and artillery – hitting the targets just before the armour arrives – and do that very precisely. Like any force, if you’re going to take a capital city you don’t go in from one side, you try to encircle it.
Big military formations – with forces of 30,000 troops and armour and all the rest of it – can only do what they’ve done on exercises and manoeuvres, so we know in advance how they’re going to fight.
There’s a predictability about the way big forces operate. There are armoured units moving towards the city, but of course they don’t always arrive in the right order, which is happening quite a lot.
What is the end game in Kyiv?
The Russians want to take the Kyiv intact. They don’t want to cause too much damage for all sorts of publicity and spiritual reasons – in fact they hate the idea of reducing Kyiv to rubble.
They want to take the city with as few civilian casualties as possible to make it look as if they’ve just rushed in and got rid of what they want to portray as a wicked old government, rescuing good, decent Ukrainians from a Nazi criminal government that they believe the West effectively put in power.
Of course, many Ukrainians do not agree with that portrayal. And if the Ukrainians are prepared to fight the city street by street then the Russians won’t be able to have the relatively bloodless takeover they are aiming for.
In fact, the whole thing will become a bit of a nightmare for them.
What are the key areas of the city Russia will be targeting?
The first obvious target is to occupy every airstrip around the city – the airfields and airports – partly for the use of their own aircrafts, but also to make sure the Ukrainians can’t use them.
Bridges will be next. The Russians need to get into the middle of the city, occupy the bridges and stop people moving backwards and forwards
Then the third area, and the most obvious one, is centres of government. They are likely to carry out what the Americans call thunder runs.
It’s a rather dramatic rumble, where fast armoured vehicles tear down the road at 40 miles an hour, packed with troops, just to see if they can get into the centre of the city.
They will head for parliament, to presidential powers and to all the governmental areas, and see who they can round up. Of course, if everybody has already fled, that suits them. They can then turn up with their puppets and install him or her into the presidential palace.
Is it worrying that a leader like Vladimir Putin has his tanks on the lawn of disused nuclear power plant Chernobyl?
I don’t think that’s a concern, and in truth if you blew Chernobyl up, not much would happen.
Even Putin wouldn’t want to create a radioactive leak.
And creating a nuclear accident would be creating a problem for himself because it could go all over the place, according to weather conditions.
What’s can we expect to happen next?
Russia’s next move over the next few days or weeks will be to declare the necessary combat operations are finished – even if they are not – and that a new constitutional arrangement is being made for the renegade state of Ukraine.
Then, depending on what the physical situation is in terms of forces and fighting (which really boils down to whether Russia has succeeded in snuffing out Ukrainian forces or whether Ukrainian resistance is able to battle on for another 48 hours), there will be months of constitutional theatre while Putin goes through a process of reconstituting a different sort of Ukraine altogether.
Of course, it will be just sort of constitutional theatre, because in reality Russia will be physically in control.
Then there will be the ‘Gestapo’ phase, which is where the security services will be picking people up who are on a list and a lot of people will disappear – including most of the present government.
However, it’s not necessarily going to run quite so smoothly. President Putin seems to fundamentally misunderstand Ukrainian society these days, and a lot could happen between now and next week.
If the Ukrainians keep on fighting, and a guerrilla war breaks out, then all of that will become impossible to carry forward.
The worst scenario for Putin is that it becomes another Afghanistan problem for Russian forces, or like Chechnya before 1999, with Russian forces attacked all the time and lots of reprisals, and lots of nasty incidents.
It would become a desperate and toxic problem, and would upset Russian society far more than Afghanistan, because these are fellow Slavs. Lots of Russians have family in Ukraine.
It would be a strategic quagmire, with Putin committing a massive strategic blunder in just about every respect. And the blunder might play itself out on the ground in a counterinsurgency campaign (COIN), which would certainly be brutal and nasty.
And very importantly, compared to the Russians in Afghanistan or Chechnya, the thing that would be different this time would that it would all be taking place in the environment of intensive social media.
So, if the Russians do go through a ‘Gestapo phase’, they wouldn’t be able to do it quietly.
What is Putin thinking?
What is happening in Ukraine?
How does Ukraine’s military compare to Russia’s?