Europe is experiencing a series of cascading border closures, rippling outward like circuit breakers tripping during a power surge. A week ago, Denmark suspended its rail link to Germany. On Monday, Germany closed its border with Austria. Austria, Slovakia, and the Netherlands all clamped “temporary” border restrictions into place.On Tuesday, Hungary sealed its border with Serbia; yesterday, Hungarian border guards used water cannons, tear gas, and truncheons to beat back a sea of migrants. This in turn forced more than 5,000 people to seek an alternate path through Croatia north to Slovenia and Germany. Croatian authorities indicated that while they want to help, Croatia’s capacity for handling migrant flows was limited to the thousands, not to the tens of thousands. And then Slovenian authorities today announced that they would reinforce their border with Croatia, potentially creating another dead end for the thousands of migrants massing in the Balkans.This was inevitable when Brussels and Berlin signaled a determination to treat the immigration problem—which is a hybrid refugee crisis and migrant moment—in purely humanitarian terms. Those languishing in the south of Europe or even in refugee camps in Turkey heard the official declarations as an open-ended invitation to the generous, prosperous, new Germany; they rushed northward and overloaded the system.European leaders had no practical plans to deal with the wave of migrants they were encouraging. While some of the border shutdowns—such as Hungary’s—were triggered by ideology, many are a matter of logistics. Germany, it turns out, has absolutely no legal immigration mechanism. It hasn’t enforced a land border since 1995. Is it any wonder it wasn’t able to process the inflow into Bavaria, despite the government’s best intentions? Now, border controls are now rippling from the desirable destinations in Europe (Germany and Scandinavia) outward to its more remote borders.In Brussels, leaders failed to agree to a refugee-sharing quota scheme earlier this week, and may now have abandoned mandatory redistribution plans entirely. As the numbers continue to mount, absent a unified border-enforcement-cum-resettlement plan, a return to national borders may be the only way some governments can see to deal with the crisis.And while all of these measures are technically “temporary”, it doesn’t take Nostradamus to see a world in which they might be extended indefinitely. The end of Schengen is now being openly discussed.European leaders acted on ideology and sentiment, counting real-world planning as a sign of backward-looking hard-heartedness. The result is that well-meaning centrists have egg on their face, and, as Adam Garfinkle put it in a must-read essay on Sunday, “One fears that if reasonable people do not somehow apply a brake to this wild excess of selfless saintliness, unreasonable people eventually will.” As the European far right grows stronger, the Continent badly needs some adults who can balance do-gooder instincts with some practical sense. Will they step to the fore in time?