MOSCOW — Russian President Vladimir Putin, posing one of the biggest security threats to Europe since World War II, is staking his legacy on an irredentist invasion of Ukraine that poses significant risks to his own country and raises worrisome questions about his ambitions to bring Kyiv to heel.

Putin’s defiant decision to use full-fledged military force represents an unprecedented level of risk-taking for the Russian leader and threatens to isolate his country even further from the West and its allies. Punishments being leveled by Western nations could land Washington in an escalatory cycle with Moscow, if Russia responds to the measures in kind.

The attack also carries a direct challenge to the post-Cold War global order. Putin’s sweeping ambition involves hammering out a new international balance, setting the scene for a club of powerful nuclear powers to dominate smaller states and carve out spheres of influence — by force if they see fit.

On the eve of his attack, Putin invoked Russian battles against invaders going back to the 1612 Battle of Moscow to depict a Ukrainian nation taken hostage by the United States and its European allies and in need of liberation. A day earlier, he remarked that using military might to resolve problems was a good thing. The main thing, he added, was to avoid weakness.

“Well, why do you think that the good must always be frail and helpless? I do not think that is true,” Putin said at a news conference Tuesday, after gaining lawmakers’ approval for military action abroad. “I think good means being able to defend oneself.”

He has multiple goals in his sights: not just toppling Ukrainian leader Volodymyr Zelensky, but also securing Ukraine’s capitulation to become a modern version of a Soviet-style satellite state, such as neighboring Belarus.

More broadly, he remains determined to reshape European security to suit Moscow and put NATO forces on the back foot through his display of military force against Ukraine. Russia’s military assault has communicated to Ukrainians that their choice isn’t between Russia and NATO — but between Russia and destruction.

On a global level, Putin seeks to communicate to U.S. partners that Washington will go only so far in backing them against existential threats.

Putin’s ‘risk tolerance’

“Our prior assumptions about his risk tolerance need to go out the window,” said Samuel Charap, a senior political scientist at the Rand Corp. think tank. He noted that Putin had taken on a “qualitatively different level of risk” with his full-scale invasion of Ukraine that would force Western capitals to recalibrate.

For years, the Russian leader has sensed the decline in the relative power of the United States and come to believe he has spotted a widening geopolitical vacuum that he can fill — in the Middle East, Africa and the Arctic, as well as closer to home.

His actions reflect a man steeped in Soviet geopolitics and traditional Russian Orthodox conservatism, fired with an almost spiritual view of his historical mission to transform his vast nation. At home, that has come with increasing repression — with his government removing opponents, quashing dissent, and hobbling Internet and press freedom with ever more vigor as his government ages.

Putin may be betting that his forces can take control of the bulk of Ukraine without significant urban fighting that could leave thousands of civilians dead. Already, his military has struck dozens of Ukrainian military targets across the country and crossed the Ukrainian border with ease. Neither Ukraine nor Russia has given official casualty counts from the battle so far, but a statement by Britain’s Defense Ministry said “heavy casualties” had been suffered by both sides.

But the initial “shock and awe” stage of a military conflict is often less difficult for an attacker than the stage that follows — as the American military learned in its invasions of Afghanistan and Iraq. Upon completing his military offensive, Putin will then need to carry out his political objective to end Western influence in Ukraine and return the former Soviet republic firmly to Moscow’s domain.

Ukraine’s Western path

One critical obstacle to that is a Kyiv political elite that has grown deeply pro-Western.

How Putin intends to replace the leadership with a group of pro-Russian Ukrainians is unclear. But U.S. intelligence has suggested as much and he signaled his possible intention to do so in his speech Thursday, when he vowed to “denazify” Ukraine and hold accountable those responsible for Ukraine’s “crimes.” He talked of a new Ukraine that can turn the page on its relationship with Russia.

While Putin said Russia does not intend to occupy Ukrainian territory, he strongly suggested that his aim was to elevate authorities allied with Moscow and possibly carve up the country using referenda similar to the one the Kremlin organized in Crimea in 2014.

Russian forces are concentrated in the east, north and south, suggesting they may seek to cut off the western part of Ukraine, a region that didn’t fall within the country’s borders before World War II. That portion of the country — which includes the cities of Lviv, Uzhgorod and Ivano-Frankivsk — has long been an epicenter of anti-Moscow sentiment in Ukraine. Without that territory, Russia may see the country as controllable by a Moscow-friendly government installed by Russia.

Keith Darden, a professor at American University who studies Ukraine, said that kind of territorial change would completely reorder the politics of the nation as a whole in a way Moscow would see as favorable.

Putin could go further. Russian state television on Wednesday aired a map of Ukraine with the territorial “presents” gifted to Kyiv by czars, Bolsheviks and Soviets. His military campaign may entail slicing away Ukraine’s coast and eastern industrialized regions, in addition to the west, leaving a small, unviable rump state, while annexing parts of the country to Russia.

Darden said Putin is risking a full-fledged break with the West. For example, he said, Russia could respond to harsh Western sanctions with a cyberattack against the United States, which would then force Washington to respond again, bringing the United States closer to a direct conflict with Moscow.

“We don’t want to go to war over Ukraine, and we have made that very explicit, but we also don’t want the war against Ukraine to go unpunished, but those two things might not be compatible,” Darden said. “It is hard to contain an escalatory cycle like this.”

Launching a war on Ukraine will isolate Russia’s economy, damage its trade and hinder technological development. It could also potentially trigger an exodus of young urban Russians and tech engineers uncomfortable with Putin’s revanchist vision who aspire to live in a modern, open world.

Isolated by choice

One of the pretexts Putin cited — the need to “denazify” Ukraine’s leadership and save the people from the Western governments that had taken them hostage — horrified many Russian liberals. It risks leaving Putin a global pariah isolated from all but the handful of autocrats he has cultivated. On Wednesday, several antiwar protests broke out across Russia, but security forces in many cases detained demonstrators.

If there was any doubt about whether anyone in Putin’s circle would challenge him over the wisdom of an open war with Ukraine, it was dashed during the extraordinary spectacle of his Security Council meeting on Tuesday. Putin barked “Speak directly!” at his trembling foreign spy chief, Sergei Naryshkin, who fumbled his words like a boy in front of a schoolmaster, eyes bulging with fear.

Putin used the carefully staged televised episode to co-opt Russia’s entire political leadership group in a war for which there was no legal basis. In his speech, Putin cited Article 51 of the U.N. charter, which enshrines a nation’s right to self-defense if attacked.

Over the past two years, under the veil of the coronavirus pandemic that kept him isolated and brooding, Putin has made a profound shift.

Russians had been contemplating a possible political transition in 2024, when Putin conceivably could step down or bring on a clear heir to replace him in Russian politics. Few thought he would try to cling to power until 2036, when he would turn 84. But he engineered a vote changing the constitution in 2020, allowing him to stay that long.

He also grasped for a more forceful set of tools — to subdue opposition at home and also in Russia’s neighborhood.

In Belarus, he bailed out another autocrat, President Alexander Lukashenko, when he faced anti-government street protests. Putin leveraged that political debt to co-opt Belarus as a staging ground for his military operation against Ukraine.

Ukraine is a far greater challenge, with its jostling, often chaotic political and business rivalries and its class of pro-Western activists.

Putin tried multiple approaches to undermine Ukraine’s growing Western bonds over the years. When one failed, he escalated. He had political allies ensconced in Kyiv for years. But Ukrainians launched two uprisings in 2004 and 2013 to oust them and build ties with the West.

After the Maidan uprising eight years ago, Russia annexed Crimea and fomented a separatist rebellion in eastern Ukraine. It foisted a 2015 peace deal on Kyiv, forcing it to give two regions autonomy, meaning they could veto Ukraine’s pro-Western shift.

That didn’t work either, because the deal was never implemented. From 2019, Russia issued 800,000 Russian passports to Ukrainians in the separatist regions, forming a pretext for military action to defend them.

In a final escalation, Putin declared that Ukraine was committing “genocide” against the separatists, called the rebel regions independent countries and launched a battle to topple Zelensky, a former comedian who played the Ukrainian president in a popular TV series.

Jailed opposition leader Alexei Navalny posted on Twitter in an English-language thread that Putin resembled a drunken grandfather who spoiled family celebrations.

Navalny, who is facing another Russian trial that could add 15 years to his more than two-year prison sentence, wrote: “It would be funny if the drunk grandfather was not a man of 69 who holds power in a country with nuclear weapons.”

Sonne reported from Washington.