President Barack Obama arrived here early Friday to attend a NATO summit meeting that is unfolding against a tumultuous backdrop of renewed Russian aggression in Eastern Europe, a migrant crisis and terrorism fears on the Continent’s southern rim and internal disarray in the wake of Britain’s vote to leave the European Union.
Obama will confront all those forces in a hectic two days of meetings during his last appearance at a NATO meeting. But it is the last challenge that may prove the most vexing: Britain’s “Brexit” vote utterly changes the landscape, experts said, not just for the EU but also for the trans-Atlantic alliance that lies at the heart of NATO.
NATO will announce a raft of military initiatives to deal with the threats from Russia and the tide of refugees fleeing the civil war in Syria. What Obama and the other leaders may find more elusive are the arguments to convey why alliances like this remain vital, at a time when the citizens of Europe’s most important military power just voted to go it alone.
“There hasn’t been another inflection point like this for the alliance since the fall of the Berlin Wall and the dissolution of the Soviet Union in ’89 to ’91,” Douglas E. Lute, the U.S. ambassador to NATO, told reporters Wednesday. “So this is a bit of a historic point.”
The White House has been circumspect in speaking publicly about the fallout from the British vote. Administration officials tend to confine their comments to hopes that the process will be handled in an orderly manner, so as not to harm the economy or disrupt financial markets. Such reticence suggests the White House, like many in Britain itself, is still in denial, in the view of some analysts.
“The White House has yet to fully acknowledge the shift in Europe today and the challenges that it faces,” said Heather A. Conley, director of the Europe program at the Center for Strategic and International Studies.
Administration officials said they expected Obama to meet one on one in Warsaw with Prime Minister David Cameron of Britain to discuss what comes next after the referendum. Afterward, they acknowledged, the president would need to make an “affirmative case” for the value of the European Union, and more broadly, for an integrated world.
Benjamin J. Rhodes, the deputy national security adviser, said, “All leaders in Europe and the United States, including himself, have a responsibility in the face of all of these challenges to the trans-Atlantic order we built, to make the case.”
If they did not, Russia would seek to exploit the divisions in Europe. “That cannot simply be swept under the rug,” Rhodes said.
To some extent, Russia is the familiar threat at this meeting. Its aggression toward Ukraine dominated the last NATO summit meeting in Wales, and two years later, the alliance has put in place military measures to deter it. NATO is strengthening its eastern flank by deploying four rotational battalions, one led by the United States, in Estonia, Latvia, Lithuania and Poland.
The alliance is expected to declare that the initial phase of its missile-defense system is finally operational. And the leaders are scheduled to discuss ways to deter members from cyberattacks, having elevated cyberwarfare to the same status as air, land and naval warfare.
Over dinner Friday night, the leaders will discuss how best to deal with President Vladimir Putin of Russia. Obama will be able to deliver a briefing, having spoken with Putin the day before he left Washington.
Officials suggested the conversation was starchy, with the president scolding Putin for a “significant uptick in fighting in eastern Ukraine” and urging him to press the Syrian government to abide by a partial cease-fire.
Rhodes disputed a report from the Kremlin that the two countries were moving toward military cooperation in Syria.
“If the trends of the last several weeks continue,” he said, referring to recent Russian behavior regarding Syria, “they’ve been moving in the wrong direction.”
Administration officials said Obama would emphasize ways NATO could cooperate militarily with the EU — modest but symbolically significant gestures to counter the rifts exposed by the British vote. Those include joint military exercises, coordinating cyberdefense strategy and joint patrols of the central Mediterranean Sea.
After the Warsaw meeting, Obama will get a brief respite from Europe’s turmoil by visiting Spain — though even there, officials have been unable to form a new government since recent elections.
In Seville, he is scheduled to do some sightseeing and speak to the troops at the U.S. naval station in Rota. The next day, in Madrid, he will have lunch with King Felipe VI and meet with Spain’s caretaker prime minister, Mariano Rajoy.
White House officials said Obama was traveling to Spain because it was the last big European Union country he had not visited as president.