FEW people have summed it up better than former British intelligence chief Sir Alex Younger. “A failure of the imagination,” he called it, speaking of the West’s mistaken belief that “history had changed back in 1991” with the collapse of the Soviet Union.

It was on Christmas day of that same year when then Soviet President Mikhail Gorbachev made his now famous speech announcing the dissolution of the Soviet Union, with the words: “We’re now living in a new world.”

The Cold War it appeared was over, but not it would seem in the mind of a certain lieutenant colonel in Russia’s KGB foreign intelligence service who immediately ­resigned that year to begin a political career.

Today that same former spy, Vladimir Putin, is president of Russia. This past week in a rerun of those dark years of the Cold War when Soviet tanks crushed those audacious enough to defy the Kremlin’s will in places like Budapest in 1956 and Prague in 1968, it was Putin who issued the order for a new Russian military juggernaut to bring others to heel.

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As I write Kyiv, the capital city of Ukraine a European city of over three million people is ­under siege and the whole of this democratic nation subjected to a Russian invasion ­devastating in its impact. Vladimir Putin has brought war back to Europe.

Such is the pace of events on the ground in Ukraine that the challenge in writing about it is keeping up with what is happening. But if one thing is clear it’s that Putin is determined to remove as quickly as possible the existing government of Ukrainian president Volodymyr ­Zelensky and replace it with a puppet regime in Kyiv. Along the way Putin will also want to ensure the renunciation of any ­ambition Ukraine might harbour of joining the West via the EU or Nato.

Zelensky himself in an earlier video message made clear that he believes ­Russia had marked him down “as the number one target,” and his family “the number two target”. He added that ­Russia “want to destroy Ukraine ­politically by destroying the head if state”.

“I am pretty sure that Putin does not want Zelensky alive,” the Financial Times quoted one western military ­official as saying.

“We’re dealing here with a ­gangland boss who does not operate like a ­conventional statesman,” the official added. “Putin would like to suggest that there’s an equivalence between Zelensky and, say, Saddam Hussein in Iraq. But that’s clearly absurd.”

The National: Ukrainian soldiers take positions outside a military facility as two cars burn, in a street in Kyiv, Ukraine, Saturday, Feb. 26, 2022. Russian troops stormed toward Ukraine's capital Saturday, and street fighting broke out as city officials urged

A former comedian and actor Zelensky has been widely praised on social media for his response to the Russian invasion.

In an earlier moving speech, he vowed that Ukraine would keep fighting, saying: “When you attack us, you will see our faces. Not our backs.”

He had also posted a self-shot video ­earlier on Friday showing him and his key aides in the capital, rebuffing reports that he had fled Kyiv.

“We’re all here,” he said. “And it will stay this way.”

According to some US media ­outlets Zelensky turned down an offer by Washington to help evacuate him from Ukraine.

“The fight is here. I need ­ammunition, not a ride,” the Associated Press ­reported Zelensky as saying, citing a senior ­intelligence official with direct ­knowledge of the conversation.

The National: Police officers detain a woman in Moscow, Russia, Friday, Feb. 25, 2022. Shocked Russians turned out by the thousands Thursday to decry their country's invasion of Ukraine as emotional calls for protests grew on social media. Some 1,745 people in 54

While Zelensky continues to display great fortitude, his Russian ­counterpart President Putin continues to show ­further troubling signs of being detached from reality.

On Friday, the Russian leader urged Ukrainian soldiers to “take power into your own hands” and not to let “drug ­addicts and neo nationalists use your families as human shields”.

Putin’s remarks made in a television address were just the latest that have had Kremlin watchers expressing disquiet over the Russian leader’s disposition and frame of mind.

Just a few days ago US Senator Marco Rubio a member of the Senate ­intelligence committee and, as such, privy to ­briefings from American spies, intriguingly ­suggested in a tweet that “Something is off” with Putin. The Florida Republican added that Putin’s decision-making skills are not what they were five years ago and that “his problem now is different and ­significant”.

But with Ukrainians choosing to fight rather than listen to Putin’s rants the ­reality of what this means on the streets of Kyiv, is a city girding itself against an all-out Russian assault.

The National: FILE - Ukrainian servicemen walk by fragments of a downed aircraft, in in Kyiv, Ukraine, Friday, Feb. 25, 2022. The International Criminal Court's prosecutor has put combatants and their commanders on notice that he is monitoring Russia's

“The city has gone into a defensive phase. Shots and explosions are ringing out in some neighbourhoods. Saboteurs have already entered Kyiv,” said mayor, former world heavyweight boxing champion Vitali Klitchko as the first battles in the city erupted on Friday. “The enemy wants to put the capital on its knees and destroy us.”

With every hour that passes the fighting intensifies as Russian troops and armoured vehicles advance into Kyiv’s northern suburbs. Ukraine’s defence ministry called on residents of northern Kyiv to “make Molotov cocktails, neutralise the occupier”, while defence minister Oleksii Reznikov said 18,000 submachine guns were being distributed to citizens in the capital. As well as mobilising reservists the government also ordered all adult males between the ages of 18 and 60 to remain inside the country with many being conscripted.

After a frenetic night filled with air raid sirens and gunfire, Kyiv’s residents many having spent the night-time hours sheltering underground in carparks and metro stations, woke to what some described as an eerie silence Saturday morning.

But the respite was brief with reports posted by the Ukrainian Armed Forces on Facebook, saying that an army unit in Kyiv had repelled Russian forces on a major city avenue and that there were “heavy battles ongoing” in the Vasylkiv area of the city and “active combat” was taking place in some streets.

Russia on Friday also claimed it had captured Kyiv’s Hostomel airport, which is near the Obolon district. Control of the runway could allow Russia to transport rapidly large numbers of troops directly to the capital. But Ukrainian officials said they had repelled the attack.

The National: In this photo provided by the Ukrainian Presidential Press Office, Ukrainian President Volodymyr Zelenskyy delivers his speech addressing the nation in Kyiv, Ukraine, Friday, Feb. 25, 2022. Russian troops bore down on Ukraine's capital Friday, with

Ukrainian President Volodymyr Zelenskyy delivers his speech addressing the nation in Kyiv, Ukraine

Elsewhere across Ukraine battles ­continued in the cities of Kherson, Mykolaiv and Odesa, an adviser to ­Zelensky’s administration, Mykhailo Podolyak, said in a televised address. He claimed the situation in Kyiv was “100% controlled”.

While both Ukrainian and Russian military claims cannot be ­independently verified, both gave tallies of those killed, wounded and damage inflicted on ­military materiel.

As of yesterday morning, Podolyak said that Ukraine had killed more than 3500 Russians and captured just under 200 more.

Oleksiy Arestovych, an adviser to ­Zelensky, said Russian forces had lost about 14 aircraft including 1-2 Ilyushin-76 transport planes carrying ­paratroopers, eight helicopters, 102 tanks and 536 ­armoured personnel carriers.

The Ukrainian government’s ­emergency services meanwhile issued an update

early yesterday that at least six people were injured and dozens more evacuated from a high-rise residential building in southwestern Kyiv that was struck by Russian rocket fire earlier in the day.

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For its part Russia claimed is operations have crippled more than 800 Ukrainian military infrastructure sites so far, the ­defence ministry in Moscow said.

Ministry spokesperson Igor Kona­shenkov said 14 military airfields, 19 ­command posts, 24 S-300 anti-aircraft missile systems and 48 radar stations were destroyed. In addition, eight ­Ukrainian naval boats were hit, he said.

Russia also claimed to have captured the southern Ukraine city of Melitopol although British military intelligence ­assessments said they remained ­sceptical of this, adding that Russian forces are far from having it all their own way ­despite an aggressive and swift start to their ­invasion operations.

“Ukrainian armed forces continue to offer strong resistance,” said Lt Gen. Jim Hockenhull, the British chief of ­defence intelligence. But military analysts also warn that Russia have so far only ­deployed about one-third of the 150,000 to 190,000 troops it had massed at Ukraine’s borders and its capacity to intensify the pressure at any time remains a major cause for concern.

For the moment, all eyes are focused on the capital Kyiv which Russian troops are attempting to surround with the aim of isolating and laying siege to the capital.

But should the ­Russian advance become bogged down and fail to meet timescales and objectives the worry is that Putin might grow impatient over ­inflicting a rapid victory, and ­resort to even more destructive tactics and ­weaponry.

Among these are powerful artillery ­systems and thermobaric weapons which Russia is known to have in its armoury and used in previous conflicts in places like Chechnya and Syria. Many fear that the deployment of such weapons could leave Kyiv with similar levels of destruction inflicted previously on large cities like Grosny or Aleppo.

Thermobaric missiles contain a highly explosive fuel and chemical mix and use oxygen from the surrounding air to generate a high-temperature explosion with supersonic blast waves, making it more deadly than a conventional weapon. They can reduce cities to rubble and would cause huge loss of life.

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One Western official cited by several news outlets said that the biggest ­problem is that Putin had chosen this conflict with Ukraine and would stop at almost ­nothing to achieve his aims.

“The problem now is having ­committed himself in the way that he has, this is now not a war of choice for him, but a war of necessity. So, he will see this as a must-win conflict, and my fear is that in order to win that conflict he will resort to any means necessary with the force he has ­assembled,” the official said.

Speaking to the Financial Times, Jack Watling, research fellow at the Royal United Services Institute (RUSI), predicted that “the next week is likely to be horrendous, as Russian forces push into cities and killing increases”.

Should Russia succeed in what is ­clearly now an attempt at regime change many fear a subsequent “brutal and ­lethal ­suppression campaign,” would likely follow with the arrest and possible execution of among others Ukraine’s ­political leadership, journalists, as well as dissidents from neighbouring Belarus or Russia that are exiled in the country

As the fighting intensifies so too does the exodus out of the country by ­Ukrainian civilians. It’s estimated that about 100,000 people have crossed into Poland from Ukraine since Thursday, including 9000 who have entered from early yesterday morning Polish Deputy Interior Minister Pawel Szefernaker told a news conference.

At Medyka in southern Poland, ­refugees described a 19-mile line at the border. Ukrainians were also crossing the borders into Hungary, Romania, and ­Slovakia.

As the crisis grows Western nations are again looking for ways to respond with sanctions the first line of attack. So far, a raft of sanctions on Russia, including blacklisting its banks and banning technology exports have been implemented.

However, they have stopped short of forcing Russia out of the SWIFT system for international bank payments, but the governor of a central bank in the euro zone told Reuters news agency yesterday such a decision was “just a matter of time, very short time, days”.

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For those Ukrainians though sheltering right now from shells and missiles and those facing off against Russian tanks in Kyiv’s streets and elsewhere time could well be in short supply.

Whatever lies in store for Ukraine and its people in the immediate or long-term future, Russia’s invasion last week was a watershed moment. One that many ­commentators including ­journalist ­Lionel Barber writing in The New ­European newspaper have said will “live in infamy along with the Nazi invasion of ­Czechoslovakia in 1938; the Japanese assault on Pearl Harbour in 1941; ­Soviet tanks crushing the anti-communist ­uprising in Hungary in 1956; and ­Serbia’s invasion of Kosovo led by President ­Slobodan Milosevic in 1999”.

That “failure of imagination” as ­British intelligence chief Sir Alex Younger spoke of – the West’s mistaken belief that ­history had changed back in 1991 with the ­collapse of the Soviet Union – will doubtless prey on the minds of many Western political leaders as they watch events unfold in Ukraine. Could it be that what we are now witnessing is a decisive shift in the balance of power and the end of the post-Cold War liberal order?

That itself is quite a question. But for now, there is a more immediate one in the shape of what will or can the West and its allies do to hold Vladimir Putin to account for an act of war that is far from over but has already shocked the world.