It is only when you notice the railway lines that all the historical echoes converge. On a train line between Greece and Macedonia, where a gate protected by barbed wire has been set up to keep migrants on the Greek side of the border, men are pulling down the defences. They’ve already weakened the gate with battering rams. As they make the final assault with bare hands, a crowd pushes and yells behind them, desperate to run along those railway lines, deeper into Europe.

The sky is white and remorseless. They are all wrapped up warm against a lingering winter. Photographers jostle among the crowd, for this is news. Another day. Another assault on a European border. Good pictures, like the one above , have been splashed across the press. It is full of furious humanity and a deep enigma. Who are these people and what do they want?

Once, refugees went the other way. They needed to get out of continental Europe. Railways carried the Kindertransport west. But the biggest migration was forced and murderous, as trains took millions of people east, to the Nazis’ killing camps. Europe, as the title of a recent book by the historian Ian Kershaw puts it, has been “to hell and back” in its modern history. The most eloquent work of art about that infernal history is Tramstop, an installation by the German artist – and severely wounded Luftwaffe pilot – Joseph Beuys. Just laying out rusted rails on the ground is enough for Beuys to summon up a century of ghosts.

Now these men struggle to walk history’s rails the other way, into a Europe that for them is not haunted at all but open space, a promised land. Their faces are full of desperation, anxiety, and anger – the frustration of being kept in Greece as one country after another takes a hard line against refugees.

This picture is a tribute to the success of the European Union in transforming our continent. A Europe that in 1945 was hollowed out, charred, bloodstained, wretched, is today so peaceful, affluent and stable – yes, even with all that has happened since the financial crash – that it attracts migrants in the same way as the United States always has. Trump wants the US to build a wall to keep out Latin Americans. Macedonia already has this barbed wire fence to keep Syrians and others from entering via Greece – itself the tragic exception to Europe’s desirability, yet also the geographic point of entry across the Aegean.

They are wrong about Europe, these faces full of fury and hope. It is a continent full of fear. That railway into the Balkans really is haunted. In 1943 the northern Greek city of Thessaloniki sent 49,000 people by train to Auschwitz, of whom fewer than 2,000 survived. Europe has a history of being terrified of the other, the stranger, the enemy within or without.

Today such fears focus on pictures like this. So I can say what I like. I can insist this is an image of heroic, defiant, brave people trying to make us live up to our human responsibilities and true values. I can offer the most liberal of all liberalisms as a true key to this photograph’s meaning. It won’t make any difference.

Let’s look at the picture in another way. It shows some very angry looking men pulling down a gate. Who are they? That’s the million-dollar question, in the politics of fear. They may all be doctors, piano teachers and poets. I am looking into their eyes. It is impossible to tell. There’s a guy with glasses; he may be a student. Or is his expression a bit ... militant?

One of the men pulling the gate down wears a red hoodie – probably sensible in what looks like bleak Balkan weather – and is looking downward. It very much appears that he is avoiding the camera lens. He probably has good reasons for not wanting his portrait in the world press. Then again, does he have something to hide?

I am looking now at this photograph with the eyes of our fearful age. The fears are not as easy to dismiss as liberals would like. They seem sensible to many. How can I be sure, weighing up these men, that none have any terrorist leanings?

Just to say that is to dismiss the nightmare. No, these are fellow human beings whose action in bringing down a barbed wire border seems totally understandable. But fear does not question itself. The fear of terrorism is hard to dismiss because it seems logical. Pictures like this will ensure that migration continues to be an issue in Britain’s EU referendum. The fear they evoke will not be dismissed by calling it Islamophobia or racism. It feels like reason, rather than ignorance or prejudice. Fear always does.

Those railway lines run right back into the medieval past, when people accused of being witches and heretics were killed throughout Europe, and the blood libel against Jews began. This was particularly popular in East Anglia, where the antisemitic saints Hugh of Lincoln and William of Norwich give the lie to any delusion that we don’t share the continent’s darker inheritance. The men pulling down the gate want to enter Europe’s house. They have no idea what lurks here.