Berlin ? Shortly before the Brexit vote, Germany’s Der Spiegel magazine ran a cover story that urged the Brits: “Please don’t go.” For Germans, long the most loyal supporters of the European Union, it was unthinkable that the British would leave them.

After the Brexit shock, Der Spiegel has a new plea: “If we don’t become more passionate about the European Union, we will lose it,” writes columnist Stefan Kuzmany.

There is widespread agreement that the future of a united Europe will be decided more by emotions than facts.

In Britain, the Brexiteers made a passionate case that Brits had to wrest back their sovereignty from a faceless Brussels bureaucracy. This, they said, was the only way to stop immigration — an issue that arouses passionate emotions.

The pro-Europe campaigners put forward dry, if valid, facts: Brexit would have a heavy economic cost and couldn’t stop immigration. But, having watched the last big debate, I can confirm that the “Remain” case was boring.

The “Leave” campaign, on the other hand, played brilliantly on emotions, hailing British sovereignty and decrying Arab refugees, even though Britain admitted almost none. “If you have decisive campaigners vs. a hesitant force, the hesitant side will lose,” notes Olaf Wientzek, head of European policy for the Konrad Adenauer Foundation. “Having facts on your side is not enough.”

Of course, designing a passionate case for Brussels is tricky since there appears to be no one single reason for the steady rise in Euro-skepticism across the continent. Clearly the euro crisis and economic malaise play a role.

The Germans have long been the strongest supporters of the post-war European project. It’s easy to understand why when you travel around Berlin, with its dramatic Holocaust memorial, restored Reichstag, and remnants of the Berlin Wall.

By embedding Germany safely within Europe, the EU minimized the fears of other European states that a strong Germany would be a threat. Yet even in Germany, only 50 percent hold a favorable view of the EU, according to a recent Pew Research Center poll.

Meantime, French National Front leader Marine Le Pen rails about the need for France to reclaim its “freedom” from EU regulations, as she calls for a Frexit referendum. Only 38 percent of the French hold a favorable view of the EU, according to the Pew poll.

However, I agree with Wientzek, who says the main driver behind Euroskepticism is neither economic arguments nor the Brussels bureaucracy. “In most countries,” he says, “the buzzword is immigration or terrorism and less the EU as a monster.”

Certainly, if you read Le Pen’s words carefully, the subtext is all about immigration. She knows her most potent appeal is to those who fear — with reason — that the flow from North Africa will continue. She also knows that if France ever voted for a Frexit, the EU would die.

Immigration is the issue that arouses the most heated emotions, the one that those who want to save the European project must respond to.

Having flubbed the 2015 immigration crisis, the EU now must make a firm case that it can and will secure Europe’s borders. In other words, that it will respond to the public’s legitimate fears.

That will involve cementing a deal with Turkey that has already sharply decreased the flow of migrants and refugees reaching Greece. It will involve strengthening coast guard patrols that are now returning migrants who have set out from North Africa to cross the Mediterranean. And it must involve increased cooperation to fight jihadi terrorism.

“We need to show we can act as the European Union to deal with threats in our neighborhood,” Wientzek said. That would also involve pushing back against Russian efforts to meddle further in Europe.

None of this is easy, and it comes late in the day. But EU backers must argue decisively that Europe’s security requires unified action — and prove they are up to the task.

In making a strong case for Europe, however, Germany has a special role to play — one that goes beyond Chancellor Angela Merkel’s lead in Brussels.

Europeans either have forgotten or never knew the reason the EU was created — to cement a peaceful Europe after horrible wars.

Columnist Kuzmany mourns that Germans have become so accustomed to postwar stability that they can’t imagine any other outcome. “By forgetting the war, we have in no way exorcised the possibility of it happening again,” he said. History may not repeat exactly but that is no guarantee that Europe will remain stable.

I don’t know how this message can be communicated passionately to generations for whom World War II has no meaning, and who can’t imagine the dangers posed by a return to ubernationalism. If there were ever an argument that deserved to be made passionately, this is it.

— Trudy Rubin is a columnist and editorial board member for the Philadelphia Inquirer.