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It’s not Brexit, nor an imploding euro zone, nor caravans of desperate migrants. Rather, the coronavirus pandemic may pose the biggest challenge to European unity — and the European model — in decades. On Tuesday, the leaders of the 26 European countries in the Schengen zone, which enables borderless, free movement within much of the European Union, agreed to temporarily close their borders to non-E.U. nationals as the bloc’s governments struggled to handle the outbreak in their midst.

Already within Europe, national governments have set up barriers where there were none, halting travelers and blocking medical supplies from going to other countries. E.U. leaders on Tuesday insisted that they would guarantee free circulation of goods across the zone, even as people become ensnared in lockdowns and travel bans.

The continent is now at the heart of the pandemic, with infections still spiking. In its worst-affected country, Italy, the total number of confirmed cases rose Tuesday to over 31,000, an increase of more than 3,500 from the day before. Authorities also reported 345 new deaths, bringing the death toll to above 2,500.

The severity of the moment is apparent. Parisians fled the French capital to country abodes more conducive to social distancing after President Emmanuel Macron declared Monday that his nation was in wartime mode. “It is of course a sanitary war,” Macron said. “We are not fighting against an army, or another nation. But the enemy is here. It is invisible, elusive and it is progressing. And this requires our general mobilization.”

German Chancellor Angela Merkel sounded a similar note after announcing a domestic and international travel ban and the shuttering of bars, theaters, museums and other nonessential shops. “These are measures that have never been seen before in our country,” Merkel said, adding later that “we haven’t seen a similar situation in the 70 years existence of the Federal Republic of Germany.”

But these proclamations belie a fraying sense of unity and common purpose. Indeed, in the past weeks, far-right populists in Western Europe and illiberal demagogues in the continent’s east have groused about the bloc’s inability to either to stave off the crisis or help its more imperiled member states. With barriers coming up, some analysts already see a lasting legacy.

“The coronavirus could … become a tool in Europe’s wider, and gloomier, political battle over migration,” wrote Pawel Zerka of the European Council on Foreign Relations. “The epidemic has bolstered the cause of those who have long opposed refugees — most of them the same parties and politicians who advocate for strict border controls. But if the public debate plays up the perceived link between the virus, borders, and migrants, this will come dangerously close to arguments about national purity and racial superiority.”

Then there’s the question of how Europe relates to the rest of the world. The recent, highly symbolic Chinese shipments of medical supplies — as well as the arrival of Chinese medical experts — to a desperate Italy seemed to underscore the helplessness of the continent. “We asked for supplies of medical equipment, and the European Commission forwarded the appeal to the member states,” Maurizio Massari, Italy’s permanent representative to the European Union, told Foreign Policy. “But it didn’t work.”

Many politicians are taking note. “Just outside E.U. borders, Serbian President Aleksandar Vucic reacted bitterly to news that the E.U. this weekend imposed a bloc-wide export ban on equipment such as masks and gowns to protect medical workers,” reported my colleague Michael Birnbaum. “The restriction is intended to help jump-start countries inside the E.U. to come to one another’s assistance, but it left neighbors in the lurch.”

“International solidarity does not exist. European solidarity does not exist,” Vucic said. “The only country that can help us is China.”

In Brussels, officials are hoping this week’s meetings and efforts will be the start of a more assertive response. This includes preliminary discussions about joint risk-sharing and issuing of debt to cope with the toll of the crisis.

“As E.U. governments unleash unprecedented amounts of fiscal stimulus to keep their companies alive through the lockdown, leaders are trying to work out how they can finance the sudden burst of spending without reviving the market turbulence that threatened to tear their currency union apart less than a decade ago,” reported Bloomberg News.

But as each country slumps into a national lockdown, that sense of continental support may be fleeting. “In a recent video message, Ursula von der Leyen, the president of the European Commission, tried to show her solidarity with Italy, saying in hesitant Italian, ‘We are all Italians,’” noted the Atlantic’s Rachel Donadio. “She didn’t sound so convincing.”

“For the E.U., this is really an existential threat,” Stefano Stefanini, a former Italian diplomat who now works as a security consultant in Brussels, told The Washington Post. “If the E.U. is seen as not having done enough, or not having cared enough, or not having been up to the challenge, people will double down on the question of what is the E.U. for.”

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