President Obama has long said he intends to push the country’s approach to the world into the 21st century and away from the power politics of the past.

But now his effort to make U.S. foreign policy more modest and cooperative and less reliant on military power has run into the nostalgic nationalism of Russian President Vladimir Putin, who was a KGB officer as the Soviet Union began its collapse.

Putin’s annexation of Crimea is complete, and the Obama administration has shifted its focus to preventing a deeper Russian military incursion into eastern and southern Ukraine.

Obama is seeking to discourage any escalation by squeezing Putin’s friends and supporters with financial sanctions and by threatening to take broader action against the Russian economy. He will seek to shore up support for that strategy during meetings with skittish allies in the Netherlands, where he lands on Monday at the start of a weeklong trip abroad.

But Putin is animated by nationalist impulses and historic grievances that have proved immune to the modern tools of diplomacy that Obama is employing. While U.S. officials cite a sliding ruble and dipping Russian stock market, Putin enjoys strong approval at home and celebrates the “truth and justice” of Crimea returning to Russia after generations apart.

Whether the pressures of global capitalism — a system that Putin spent much of his life fighting — will discourage his expansionist brand of nationalism is now the question at the center of Obama’s new containment policy.

“What will be clear for the entire world to see is that Russia is increasingly isolated and that the United States is leading the international community in supporting the government of Ukraine and the people of Ukraine,” Susan Rice, Obama’s national security adviser, told reporters Friday, “and in imposing costs on Russia for its aggression against Ukraine.”

Since taking office, Obama has argued that technology and an increasingly borderless economy, stateless terrorism and aspiring regional powers have changed the world since the Cold War, which ended when he was a student at Harvard Law School.

“The basic principles that govern relations between nations in Europe and around the world must be upheld in the 21st century,” Obama said last week in announcing a new and tougher round of sanctions against Russia. “That includes respect for sovereignty and territorial integrity — the notion that nations do not simply redraw borders, or make decisions at the expense of their neighbors simply because they are larger or more powerful.”

The turn in Obama’s posture has been swift. He once supported Russia’s greater inclusion in the global economy, advocating for its successful bid to join the World Trade Organization in 2012.

That same year, Obama said that “the 1980s are now calling to ask for their foreign policy back” after Mitt Romney, the Republican presidential nominee, called Russia “without question our No. 1 geopolitical foe.”

Explaining the policy now, Rice said it “was predicated on an expectation that Russia would play by the rules of the road, the economic and security rules of the road, international law” — that is, the system Obama believes is replacing the one that existed in the last century.

“What we have seen in Ukraine is obviously a very egregious departure from that,” Rice said.

Obama has never appeared comfortable with the idea of nationalism, including his country’s own version of it. Early in his presidency, Obama was asked at an international summit if he believed in American exceptionalism, an expression of U.S. nationalism that holds that the country’s revolutionary roots and democratic ideals set it apart from all others.

“I believe in American exceptionalism, just as I suspect that the Brits believe in British exceptionalism and the Greeks believe in Greek exceptionalism,” Obama said, dismaying conservatives, who believed his answer diminished the idea.

He added, “I’m enormously proud of my country and its role and history in the world.”

But conservatives continued to criticize Obama through the 2012 campaign for failing to fully embrace the concept, even though he said repeatedly that the United States is exceptional. At times, he appeared as confused — and frustrated — by the debate as conservatives were over his early answer.

On the international front, Obama has sought to emphasize shared interests over strictly national ones, hoping to avoid the unproductive fights that have defined some important relationships in the past.

Although he has demanded better from China on human rights, he has made a shared interest in a functioning global economy central to his agenda with the Asian power. And in attempting to “reset” relations with Russia before the Ukraine intervention, Obama pursued diplomacy with Putin over Iran’s uranium enrichment program, nuclear nonproliferation, and international economic integration, with varying degrees of success.

Leading up to the Ukraine intervention, Putin had been showing some signs of subscribing to Obama’s view of the world.

He spent more than $50 billion to stage the Winter Olympic Games in Sochi, released businessman Mikhail Khodorkovsky and members of the protest band Pussy Riot from prison, and took other steps to make his government more internationally acceptable.

But after the pro-Russian government in Kiev collapsed, Putin said he had been betrayed by the West — whose governments supported the new pro-European interim leaders — and moved swiftly into Crimea.

“This is not the first step in a highly sophisticated strategy to reconstruct the Russian empire,” said Michael McFaul, Obama’s most recent ambassador to Moscow, who returned recently to his teaching post at Stanford University. “And therefore I think it gives space to the kinds of threats and warnings that President Obama is giving in regards to eastern Ukraine. It will play a part in Putin’s thinking.”

But McFaul said he doesn’t “think anybody has any illusions — or at least nobody should have any illusions — that the sanctions applied the way they have been so far are going to compel Putin to reverse course in Crimea.”

The success of Obama’s approach to Putin will depend largely on whether he can persuade European leaders to rally behind more severe sanctions, given the present fears of Russian military ambitions and economic reprisals.

The European Union last week authorized measures that could target Russia’s energy and banking sectors, and Obama announced a similar move by the United States that he warned “could also be disruptive to the global economy.”

Obama will meet Monday night with members of the Group of Seven nations — Russia’s membership in the Group of Eight is currently suspended — on the sidelines of the Nuclear Security Summit in The Hague.

The summit itself is focusing on how to prevent nuclear terrorism, an issue Russia has an interest in addressing as well. Although Putin will not attend, a lower-level Russian delegation will.

Obama will then travel to Brussels for his first visit there with European Union leaders and deliver what advisers call the trip’s “signal speech” on transatlantic relations, with the Ukraine crisis as backdrop.

He will conclude the trip with a visit to Rome — where he will meet with Pope Francis to discuss the widening gap between rich and poor — and to Saudi Arabia, which is aggrieved over Obama’s failure to use military force in Syria, the negotiations with Iran on its nuclear program, and shifting support for autocratic U.S. allies during the Arab Spring.

Jeremy Shapiro, a visiting fellow at the Brookings Institution, said Obama and European leaders are likely to stress unity in public on the steps taken against Russia.

“Privately, Obama, I think, will push the Europeans to consider further sanctions, and particularly to think in advance about reactions to further Russian escalations in Ukraine,” said Shapiro, who worked in the State Department on European issues earlier in the Obama administration. “It’s very clear that U.S. sanctions aren’t effective without the Europeans.”

Any new European sanctions would have to balance the interests of the major European economies, something Obama will probably be asked to mediate during his meetings in Brussels. Shapiro said Britain will demand “burden-sharing,” meaning not paying more for sanctions than the French and Germans.

“This will be a slow process,” Shapiro said. “It will not be as satisfying as the military moves that the Russians might do.”

Obama’s economy-focused approach has shown success in places such as Iran, a smaller country hit by far broader sanctions than Russia is facing so far. The measures, started by the Bush administration and expanded by Obama, effectively severed its oil-rich economy from world markets.

Iran’s leadership is moving to rejoin global markets through negotiations over its nuclear program, although it’s unclear whether those talks will be successful.

Putin’s brand of nationalism, though, is different from the religiously inspired and more regional ambitions of Iran.

His interest — or so Europeans fear — is in restoring Russia’s national power and global authority. Since his move on Crimea, his domestic popularity has never been higher amid international condemnation.

Putin has long argued that Russia’s wealthy, including some of those named in recent U.S. sanctions, should keep their money inside Russia and away from a global economy controlled by Western interests.

Obama’s sanctions may actually give weight to his case by sharpening Russian sentiment against the United States. After the Obama administration announced sanctions against Bank Rossiya, Putin said pointedly that he would begin to have his salary deposited there.

That confidence could change, though, if economic sanctions tighten in the months ahead.

McFaul said Putin “is a highly motivated interlocutor right now given that he has just pivoted against his own strategy” of seeking greater economic integration with Europe and the world.

“Putin is the main player there, but he is not the only player,” he said. “And over time, and sanctions always take time, that’s when they will have their effect.”