On a continent still haunted by World War II, ghostly – and ghastly – shadows of that convulsive conflict have been impossible to avoid as Europe grapples with its biggest refugee crisis since the war ended 70 years ago.
They were there when Czech authorities wrote numbers, like tattoos, on the hands of Syrian refugees arriving by railway in the city of Breclav.
When desperate people aboard other trains, believing themselves bound for their hoped-for destinations, were instead taken to camps they did not want to go to.
When an authoritarian leader declared that adherents of a particular religion were not wanted in Europe because they threaten its Christian identity.
None of these is exactly parallel or equivalent to the horrors of the Second World War, a conflagration most Europeans alive today did not experience firsthand. But they have been enough to arouse unsettling associations at a moment when the liberal values embraced by much of Europe in the ashes of that war are being severely tested by the thousands of people arriving here daily.
The migrants and refugees mostly hail from the Middle East, Asia and Africa, driven by a desire to escape violence, persecution or poverty back home. They have risked drowning at sea and suffocation in the back of unventilated vans in their quest for the safety and succor they believe they'll find here in Europe.
But they've been met by chaos and confusion in nations ill-equipped to deal with them. That was the case in Breclav, where 200 Syrians fleeing their country's civil war arrived by train Wednesday.
Waiting for them were Czech authorities charged with registering and processing the newcomers. In their attempt to maintain order, the officials assigned numbers to each person – and wrote those numbers with felt-tipped pens on the refugees' outstretched hands.
What seemed a simple bureaucratic shortcut immediately produced uncomfortable evocations of the Holocaust, of death camp inmates whose arms were tattooed with prisoner numbers by the Nazis.
Jewish and human rights organizations were aghast.
"It is an image we cannot bear, which brings to mind the entry procedures at Nazi extermination camps, when millions of men, women and children were marked with a number, like animals, before being sent to their deaths," said Ruth Dureghello, a Jewish community leader here in Rome.
The Czech government quickly halted the practice, saying it had intended nothing malicious or sinister. But the incident showed how long the shadows are that Europe's darkest days continue to cast over the continent.
Those shadows also appeared in nearby Hungary, which has quickly turned into one of the epicenters of the crisis.
Hundreds of migrants were engaged in a standoff this week with authorities at Budapest's main railway terminal. After allowing some to journey west to their preferred destinations – richer countries such as Germany and Sweden – Prime Minister Viktor Orban's government abruptly canceled international train services, stranding the migrants in a nation that most of them want to leave.
There have been protests and scuffles with police. Despairing refugees, waving useless train tickets that devoured hundreds of dollars from their meager supplies of cash, appealed to the United Nations for help. Sensing opportunity, human smugglers are hawking their sometimes fatal services.
On Thursday, the authorities seemed to relent, allowing hundreds of people to board trains they thought were headed to Austria or Germany. Carriages soon overflowed with people.
But Orban's government now appears to have been playing a cruel trick. The trains pulled out of Budapest and headed west, but stopped barely 20 miles outside the city, where stunned passengers were ordered off to be registered at a camp for migrants in the town of Bicske.
"No camp! No camp!" many chanted, in a scene that revived memories of trainloads of people borne to other camps in Central Europe against their will.
"Germany! Germany! We want to go to Germany!" others cried, underscoring what has become perhaps a surprising historical irony of the present crisis.
Where once thousands of people tried frantically to get out of Germany, fearing the rise of Hitler and his diabolical policies, thousands now are trying – in some cases, literally dying – to get in. And the government in Berlin is welcoming them: It has pledged to take in an astonishing 800,000 asylum seekers, which far exceeds the total that the other 27 European Union countries, combined, have committed to accepting.
Human rights groups criticize what they say is the heartlessness of rich nations that have tried to bar the door to refugees, especially on a continent where Jews and other persecuted groups were unable to find safe havens in their hour of need.
Galvanized – or shamed – by the heart-wrenching photos this week of a Syrian toddler whose lifeless body washed up onto a Turkish beach, some European countries are rethinking their stands.
Under political and popular pressure, British Prime Minister David Cameron announced Friday that his country would receive "thousands" more refugees than originally planned. Ireland is also increasing the number of asylum seekers it will accept.
Germany's generosity, however, has sparked an ugly war of words with Hungary. Orban accuses Chancellor Angela Merkel of encouraging migrants to come to Europe when she should be discouraging them and of wreaking havoc on his country.
A right-wing nationalist with a huge majority in the parliament, Orban was widely denounced last week when he singled out a particular religion and its followers as undesirable – an attitude that stained Europe with blood in the not-so-distant past. Orban declared that absorbing hundreds of thousands of mostly Muslim migrants into the EU, home to half a billion people, would threaten Europe's "Christian values system."
"We have a right to decide that we do not want a large number of Muslim people in our country," Orban said. "I do not see any reason for anyone else to force us to create ways of living together in Hungary that we do not want to see."
Other European leaders retorted that Christian values call for treating the poor and dispossessed with compassion.
"For a Christian, it shouldn't matter what race, religion and nationality the person in need represents," said EU President Donald Tusk, a former prime minister of Poland.
This is the continent whose leaders vowed "Never again" after the political and moral calamity of World War II. The European Union was created to help make good on the promise to uphold democracy and human rights.
How well it can continue to lay the ghosts of the war to rest will only be seen in the days ahead.