WHAT happens at Europe’s borders often telegraphs momentous change. The Soviet blockade of Berlin in 1948 foreshadowed the cold war. The scrapping of a Hungarian fence on the frontier with Austria in May 1989 doomed Soviet rule in eastern Europe months before protests toppled its leaders. Now the reimposition of some border controls by Germany and Austria, to stanch the flow of refugees and migrants, is the harbinger of something dramatic: the erosion and possible demise of the Schengen free-travel area, one of the European Union’s most striking achievements. For the past two decades anyone in the 26 European countries of the Schengen area, including some outside the EU (but excluding Britain and Ireland), could travel within this zone without being troubled by customs or passport controls. Named after the town in Luxembourg where the agreement was signed, Schengen makes trade and travel easier, and is a tangible manifestation of the EU’s “ever closer union”.

But as with that other grand project, the euro, Schengen is only a partial act of integration: external borders, migration policies and policing remain in the hands of national governments. As with the euro, an outside shock has destabilised Schengen and embittered relations between EU states. The influx of migrants has made a joke of the EU’s asylum rules. Refugees are supposed to seek sanctuary in the first EU country they reach—typically Italy or Greece. But Schengen makes it easy for them to push on to the country most likely to welcome them, or where they can find friends, relatives and jobs.

Many head for prosperous, generous Germany. Angela Merkel, the chancellor, at first cast aside the rules to preserve Schengen, amid touching scenes of Germans welcoming refugees. But, unable to cope, she now wants to restore order to the system. So Germany has imposed border controls on the frontier with Austria, which has restricted movement across the frontier with Hungary, which has in turn started imprisoning migrants who cross illegally from Serbia.

Schengen rules allow countries to impose temporary controls to deal with extraordinary events. Yet the impact of Germany’s action is far-reaching. If such a big place at the heart of the EU can break the unspoken taboo against suspending Schengen, then others will have fewer qualms about following suit. In France, for example, politicians from the centre- and far-right may well actively work for Schengen’s abolition.

INTERACTIVE: Explore border fences between countries around the world Suspending Schengen is just a sticking plaster for Europe’s refugee crisis, which could persist for many years; migrants arriving in Europe will search for weak points at frontiers and burst through them. The crisis demands interventions at every stage, from working for a ceasefire in Syria to helping Turkey and Lebanon deal with their vastly larger numbers of refugees. Crucially, at home, Europeans must share the task of taking in asylum-seekers, hard though this will be. (If sent to a less-attractive country, some may head straight back to Germany.) Yet few places seem to share Germany’s Willkommenskultur. At a meeting of interior ministers on September 14th eastern European countries blocked plans for 120,000 refugees to be resettled across the EU under a system of quotas.

The stakes in Europe

This beggar-thy-neighbour mindset is reckless. It will ultimately lead to the breakdown of Schengen, and a European freedom will have been lost. The idea that EU leaders can act in the common interest will have suffered yet another blow. The crisis has already strengthened anti-immigrant, anti-EU populist parties; its chaotic mismanagement will boost them still further. And it will do nothing to help pro-Europeans arguing the merits of staying in the EU in Britain’s looming referendum. If the euro zone is stagnant, Britain leaves and Europeans can no longer travel freely, citizens might then ask: what exactly is the point of the EU?