The keys to the meeting between Biden and European leaders 1:06
(CNN) --
President Joe Biden is in Europe to usher in the post-Cold War era.
For the first time in at least 30 years, a US president has arrived with the continent shaken by Russian aggression and shaken by the return of brinkmanship on nuclear policy.
The West is also mourning its shattered illusion that it had entered an era of perpetual peace.
Biden's visit to address NATO and European Union leaders in Brussels and his trip to Poland, a front-line alliance state, will underscore how the world changed, likely irreversibly, as soon as the first tank Russian crossed the Ukraine border four weeks ago.
For three decades since the fall of the Soviet Union, presidents have traveled to Europe and romanticized the West's victories over Nazism and Communism.
Standing among the dead Americans in a World War II D-Day cemetery in Normandy or praying in an idyllic square in Prague or Warsaw, American commanders-in-chief have often said that transatlantic ties are unbreakable and forever.
The United States formally declares that the Russian Army has committed war crimes in Ukraine
However, in recent years, it seemed that the presidents and their audiences followed by inertia.
The passing of the Great Generation severed the emotional bond of memory between Americans and Europeans of World War II.
It's been more than three decades since Europeans had to worry about bomb shelters, and people with strong memories of the Cold War are in their middle ages.
European leaders cashed in their peace dividend on health care systems and neglected their military.
And the United States looked to the rise of Asia and its next rival superpower, China.
A geopolitical wake-up call
Those unbreakable ties, and the reason for them, no longer seemed as relevant or necessary in the age of borderless Instagram, especially since the Russians, rarely seen foes 40 years ago, now pack glitzy venues in London and Nice.
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Zelensky asks the Italian parliament for more sanctions against Russian oligarchs 0:49
But Russian President Vladimir Putin, fueling the grievances sown when he watched the fall of East German communism as a KGB officer and obsessed with reviving Russian greatness, changed all that.
In the process, he reminded the West of what it was for, jolting governments like Germany out of their post-Cold War complacency, and showing that the United States is still serious about the transatlantic alliance.
A new Iron Curtain has descended over Europe, this time a virtual one of economic sanctions that has cut off airline connections, seized oligarchs' money and shut down Starbucks, Apple Stores and Formula One races in Russia.
NATO is sending battle groups to frontline states like Hungary, Romania, Bulgaria and Slovakia.
The alliance is locked in a sudden proxy war with Russia in Ukraine, funneling hundreds of anti-tank and anti-aircraft missiles at President Volodymyr Zelensky's forces.
Meanwhile, Russia's ferocious carnage of civilians and city-shattering bombings in Ukraine and the exodus of millions of refugees to Europe echo the worst passages in the continent's blood-soaked 20th-century history.
Depending on your point of view, the West and Russia are now fighting the last fight of the Cold War or the first of a new era of confrontation, as autocracies like Moscow and Beijing form a broad hostile front against Western-style democracy.
"If Putin succeeds in this aggression with some gains, he is likely to try this again: against Ukraine, against others, he is likely to go ahead. Therefore, he must be absolutely defeated," said Jonatan Vseviov, secretary general of the Ministry. of Estonian Foreign Affairs, to CNN in Washington on Wednesday.
Or as the President of the European Council, Charles Michel, said in an interview with CNN's Christiane Amanpour: "We must make sure that Putin is defeated... This is a security issue, for the future of Europe and the future of the world." .
Biden's visit is a historic turning point
This is why the current visit by an American president, who remains the ultimate guarantor of European security nearly 80 years after World War II, is so critical.
Biden's visit looks like his own turning point in history.
In this new era, the West will once again try to deter and contain Russia as it tries to bolster the fight for democracy and independence of Ukraine, which is not a member of NATO, while avoiding a direct confrontation with Russia that could go nuclear.
This appears to be the biggest strategic challenge facing the West at least as long as Putin is in power, no matter how the war in Ukraine ends.
And there is no guarantee that a post-Putin Russia will be more sympathetic to the West, especially if punitive sanctions further turn the power elite and ordinary Russians against the United States and Europe.
The stakes mean Biden's mission is comparable to presidential trips that coincided with turning points in the Cold War.
These include President Ronald Reagan's first meeting with the last Soviet leader, Mikhail Gorbachev, in Vienna in November 1985, which started a chain of events that eventually ended the Cold War.
There were many critical presidential trips to Europe during the standoff between the Soviets and the West.
But Biden's also deserves a mention at the same time as the 1961 trip when President John Kennedy received a terrifying rebuke in the Austrian capital from Soviet leader Nikita Khrushchev, precipitating the Cuban Missile Crisis the following year. ,
Merge alliance unit
Biden's mission is not just rich in symbolism.
It represents his best chance yet to meld the unexpected unity of purpose in the alliance, against which Putin clearly bet, into a more permanent posture to confront Russia in a war in Ukraine that has no clear exit ramps and could last for more months.
Biden and his European counterparts know that Putin will be alert to even the slightest signs of division over what to do next.
Ukraine asked for military help.
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However, tough negotiations loom over tightening sanctions, especially over the US desire for key EU powers to divest from the Russian energy sources they depend on and keep the money flowing. in Moscow despite the toughest sanctions on record.
Biden left Washington on Wednesday warning that with Russia's infantry advance bogged down, Putin might decide to use chemical weapons in Ukraine.
Western nations will have to decide how they would respond to such an escalation, and whether there will be any change in the West's resolve not to confront Russia directly in Ukraine.
Meanwhile, Zelensky is expected to make the latest of his highly effective calls for more help from the West, as his country's heroic resistance prompts Russian forces to launch ever more aerial bombardment of civilians.
Biden says the threat of chemical weapons “is real” 1:00
Normally, international summits are scripted affairs that exist in high-security bubbles in which the rest of the world seems distant.
But the constant images of the slaughter of civilians in Ukraine and the falsehood of Putin's assault on an independent and sovereign country will make this meeting different.
The fear of how Putin will respond if he is cornered or desperate, especially given the rattling of nuclear sabers early in the crisis, will also occupy leaders' minds.
History offered them a warning as they prepared to head to Brussels.
A 96-year-old Holocaust survivor, Borys
Zelensky mourned the death of Holocaust survivor 1:12
, was killed on Friday in the Ukrainian city of Kharkiv.
Romanchenko survived spells in the Buchenwald, Peenemünde, Dora, and Bergen-Belsen camps during World War II.
But he could not escape Putin's monstrous bombardment.
His death not only exposes the Russian leader's cruel lie that he is waging a war to achieve the "denazification" of Ukraine;
he puts Western leaders on notice that they face a defining moment in Europe's renewed battle between tyranny and freedom.
Conflict Russia - UkraineNATO