In 2014, when waves of refugees began flooding into western Europe, citizens and officials alike responded with generosity and openness. Exhausted refugees spilled out of trains and buses to be met by crowds bearing gifts of clothing and food, and holding up placards that read “Welcome Refugees.”

This was a honeymoon that could not last. Some of the upcoming difficulties had been anticipated: that the newcomers did not speak the local languages, might be traumatized, would probably take a long time to find their footing, and had brought their ethnic, religious and sectarian conflicts with them, causing them to get into battles with each other. All of these things happened but—as Angela Merkel promised—were manageable. “Wir schaffen das.”

But there was one development that had not been expected, and was not tolerable: the large and growing incidence of sexual assaults committed by refugees against local women. These were not of the cultural-misunderstanding-date-rape sort, but were vicious, no-preamble attacks on random girls and women, often committed by gangs or packs of young men. At first, the incidents were downplayed or hushed up—no one wanted to provide the right wing with fodder for nationalist agitation, and the hope was that these were isolated instances caused by a small problem group of outliers. As the incidents increased, and because many of them took place in public or because the public became involved either in stopping the attack or in aiding the victim afterwards, and because the courts began issuing sentences as the cases came to trial, the matter could no longer be swept under the carpet of political correctness. And with the official acknowledgment and public reporting, a weird and puzzling footnote emerged. Most of the assaults were being committed by refugees of one particular nationality: by Afghans.

Actually Afghans should not even have been part of the refugee tide, at least not in significant numbers. It was the Syrians who were expected. Afghanistan, a place of lingering and chronic conflict, is no longer on the official refugee roster—that’s reserved for acute political and military emergencies. Still, European authorities and the public were sympathetic, and could understand why Afghans would want to leave a country rife with suicide bombings and empty of opportunity. Also, Europeans held a baseline positive sentiment towards Afghanistan. Many baby-boomer Europeans had, in their hippie days of yore, traversed that country in the legendary VW buses, and retained fond memories of friendly, hospitable people. Later everyone had mourned the loss of the Bamiyan Buddhas and felt for the poor people suffering under Taliban rule. And after that, NATO had been part of the “coalition of the willing.” Europeans were predisposed to be positive towards Afghan refugees. But it quickly became obvious that something was wrong, very wrong, with these young Afghan men: they were committing sex crimes to a much greater extent than other refugees, even those from countries that were equally or more backward, just as Islamic and conservative, and arguably just as misogynist.

This is not an article that has been fun for me to write. I have worked on issues related to refugees for much of my professional life, from the Pakistani camps during the Soviet occupation of Afghanistan to Yemen, Sudan, Thailand, Ethiopia, Djibouti, Lebanon, Bosnia, Nicaragua and Iraq, and have deep sympathy for their plight. But nowhere had I encountered a phenomenon like this one. I had seen refugees trapped in circumstances that made them vulnerable to rape, by camp guards or soldiers. But for refugees to become perpetrators of this crime in the place that had given them asylum? That was something new. Further, my personal and professional life has endowed me with many Afghan and Afghan American friends, and there is nothing collectively psychopathic about them. They are doctors, shopkeepers, owners of Japanese restaurants, airport sedan drivers, entrepreneurs, IT experts, salesladies at Macy’s—they’re like everyone else. The parent generation tends to be a bit stiff, formal and etiquette conscious. It is impossible to imagine any of them engaging in the sort of outlandish, bizarre and primitive sexual aggression their young compatriots are becoming infamous for. Yet here we are.

A few weeks ago, the Austrian city of Tulln declared a full stop to any further refugee admissions. As the mayor made clear, that decision was aimed at Afghans, but for legal and administrative reasons it could only be promulgated in a global way. That had not been the city’s intention—to the contrary, it had just completed the construction of an expensive, brand-new facility for incoming asylum seekers, which would now, the mayor declared, be given over to another purpose. His exact words: “We’ve had it.” The tipping point, after a series of disturbing incidents all emanating from Afghans, was the brutal gang rape of a fifteen-year-old girl, snatched from the street on her way home, dragged away and serially abused by Afghan refugees.

And that was just one in a string of outrage-inducing occurrences, all of them going to the account of Afghans.

A while before, in Vienna, a young female Turkish exchange student had been pursued into a public restroom by three Afghan refugees. They jammed the door shut and proceeded to savagely attack her. Grabbing her by the neck, they struck her head repeatedly against a porcelain toilet bowl to knock her out. When that failed to break her desperate resistance, they took turns holding her down and raping her. The young woman required a hospital stay, after which—too traumatized to resume her studies—she fled home to Turkey, where she continues to be depressed and miserable, unable to process what happened and unable, in a conservative Muslim society, to talk about her experience to anybody except one best friend and confidante.

It took a while for the pattern to be recognized because, until recently, western European media deliberately refrained from identifying an assailant’s refugee or asylum status, or his country of origin. Only when the correlation became so dramatic that it was itself newsworthy did this policy change. At that point, it became clear that the authorities had known about, and for political reasons had deliberately covered up, large-scale incidences of sexual assault by migrants. For example, a gang of fifty Afghans who terrorized women in the neighborhood of the Linz train station had been brushed off by a government official with the remark that this was an unfortunate consequence of bad weather, and that once summer came the young men would disperse into the public parks and no longer move in such a large, menacing pack. The public was not amused.

I could write the same report about Sweden, Germany, or any other country of asylum in Europe, but I am focusing on examples from Austria because that’s the European country I come from and know best. So let’s take a look at the Austrian press. This from Österreich, the daily newspaper distributed for free on public transit and thus read, basically, by almost everyone. Front page: Afghan (eighteen) attacks young woman at Danube Festival. “Once again there has been an attempted rape by an Afghan. A twenty-one-year-old Slovak tourist was mobbed and groped by a group of men. She managed to get away, but was pursued by one of them, an Afghan asylum seeker who caught her and dragged her into the bushes. Nearby plainclothes policemen noticed the struggle and intervened to prevent the rape at the last moment.” Page ten: “A twenty-five-year-old Afghan attempted to rape a young woman who was sitting in the sun in the park. Four courageous passersby dragged the man off the victim and held him until the police arrived.” Page twelve: “Two Afghans have been sentenced for attempting to rape a woman on a train in Graz. The men, who live in an asylum seekers’ residence, first insulted the young woman with obscene verbal remarks before attacking her. When she screamed for help, passengers from other parts of the train rushed to her aid.”

Let’s leave aside the reprehensibility of this conduct for the moment and focus instead on its logic or lack thereof. Can these men possibly expect that their attempts will be successful? Do they actually think they will be able to rape a woman on the main street of a town in the middle of the day? On a train filled with other passengers? In a frequented public park in the early afternoon? Are they incapable of logical thought—or is that not even their aim? Do they merely want to cause momentary female hysteria and touch some forbidden places of a stranger’s body? Is that so gratifying that it’s worth jeopardizing their future and being hauled off to jail by scornful and disgusted Europeans? What is going on here? And why, why, why the Afghans? According to Austrian police statistics, Syrian refugees cause fewer than 10 percent of sexual assault cases. Afghans, whose numbers are comparable, are responsible for a stunning half of all cases.

Type two words into Google—Afghane and Vergewaltigung—and a cornucopia of appalling incidents unfolds before you. The mentally retarded woman in Linz, kidnapped, dragged to an Afghan refugee’s apartment and raped until she was finally able to escape into his bathroom, lock herself in and, as he battered at the door, crank open the window and scream for help. Incidents like that one point to a cold-blooded predator, with planning and premeditation.

Others are merely baffling. Public swimming pools are confronted with epidemics of young Afghan men who think it a good idea to expose themselves, whipping off their pants and standing there until tackled by the lifeguards and removed from the premises with orders to never return. Let’s be charitable: let’s assume that at some point, one or two of these young men might have heard stories of nudist beaches and thought to join in. But that’s hardly an explanation. Seriously; in a foreign country where your legal standing is tenuous, wouldn’t you cast a quick glance around to ensure that you are not the first and only man thus flaunting his ornamentation, before engaging in conduct that your entire upbringing has taught you to consider unthinkable? Come on!

Plus, within hours or days of their arrival, the Afghan-refugee grapevine educates newcomers as to the ins and outs of navigating the country: what offices to go to and what to say when you get there, where to apply for additional aid, where to find free housing and so on. If they can learn all of that, they can figure out the dress code.

So again: what’s going on? Why is this happening? And why the Afghans? A few competing theories are in circulation.

First: “They get drunk.” One of my interlocutors, a diaspora Afghan who has lived in Vienna for decades and works as a certified court translator and advisor, and thus is intimately familiar with these cases and the persons involved, dismisses this explanation out of hand. Rather, he says, word has gotten out that claiming to have been mentally incapacitated during the commission of a crime—including from alcohol or drugs—counts as an extenuating circumstance. Often, he relates, the defendants will have been inadequately briefed and will put this excuse forward ineptly. For example, they will say that they drank two beers and from these blacked out, remembering nothing of their subsequent actions. This theory also does not explain why Afghans should be more prone to alcohol-induced sexual aggression than other young refugee men from comparable backgrounds.

A second theory hypothesizes confusion caused by a clash in cultural values. These young men, the theory holds, come from a country where women are mere dark silhouettes completely hidden under pleated burqas. Confronted with girls in tank tops and short shorts, they lose their grip on sanity and their hormones run away with them. This theory, in addition to being borderline blame-the-victim offensive, does not hold water. Again, the same reaction should then also be shown by other young men from strict Islamic societies where gender segregation is the norm; why would only the Afghans react this way? And how does it explain cases such as that of the seventy-two-year-old pensioner, out walking her dog when attacked, beaten and raped by a young Afghan? Or the schoolboy, kidnapped and gang-raped in Sweden by a group of Afghans?

Indeed, if we review the pattern of the attacks, we can soon dismiss this theory. Typically, the preferred targets are not what stereotype might imagine, provocatively dressed young women that a confused Muslim from the ultraconservative hinterland misinterprets as promiscuous. No; often, the victims are mothers with small children. I am guessing that to a predator, they appear to be easier targets, because it is assumed they will be handicapped in their ability to fight back, but there may also be some more Freudian dimension that I am missing.

In one recent case that raised a huge public outcry, a woman was out for a walk in a park on an elevation above the Danube. With her she had her two children, a toddler plus her infant in a baby carriage. Out of the blue, an Afghan refugee leapt at her, threw her down, bit her, strangled her and attempted to rape her. In the struggle, the baby carriage went careening towards the embankment and the infant almost plunged into the river below. With her second child looking on aghast, the woman valiantly fought off her assailant, ripping the hood off his jacket, which later made it possible for an Austrian police dog to track him down.

In another incident, two young women were on a midday stroll in the pedestrian zone of a small Austrian town, pushing their babies in prams before them, when they were abruptly attacked by several Afghan refugees, who lunged at them and ripped off their clothing but were apprehended before they could do further damage. It’s clear that such events antagonize the general public. It’s also clear that we can dismiss the “they were drunk and didn’t know what they were doing” theory, as well as “they thought the women were asking for it.”

This brings us to a third, more compelling and quite disturbing theory—the one that my Afghan friend, the court translator, puts forward. On the basis of his hundreds of interactions with these young men in his professional capacity over the past several years, he believes to have discovered that they are motivated by a deep and abiding contempt for Western civilization. To them, Europeans are the enemy, and their women are legitimate spoils, as are all the other things one can take from them: housing, money, passports. Their laws don’t matter, their culture is uninteresting and, ultimately, their civilization is going to fall anyway to the horde of which one is the spearhead. No need to assimilate, or work hard, or try to build a decent life here for yourself—these Europeans are too soft to seriously punish you for a transgression, and their days are numbered.

And it’s not just the sex crimes, my friend notes. Those may agitate public sentiment the most, but the deliberate, insidious abuse of the welfare system is just as consequential. Afghan refugees, he says, have a particular proclivity to play the system: to lie about their age, to lie about their circumstances, to pretend to be younger, to be handicapped, to belong to an ethnic minority when even the tired eye of an Austrian judge can distinguish the delicate features of a Hazara from those of a Pashtun.

I see his point. In the course of my research, I encountered thirty-year-olds with family in Austria who were passing themselves off as “unaccompanied minors.” I met people misrepresenting an old traffic injury as proof that they had been tortured. I learned of an Afghan family that had emigrated to Hungary two decades ago. The children were born there and attended Hungarian schools. When the refugee crisis erupted, enticed by news of all the associated benefits, this family decided to take on a new identity and make their way to Sweden on the pretense of being brand-new refugees. Claiming to have lost their papers during their “flight,” they registered under new assumed names and reduced the ages of their children; the mother declared herself a widow. Now ensconced in comfortable free housing along with their hale, hearty and very much alive father—whom they pass off as an uncle—with a monthly welfare check, they are smug parasites leeching off the gullibility of Sweden’s taxpayers.

Western legal systems are meticulous and procedural, operate on the basis of rules and rights and forms and documents, and consider you innocent until proven guilty. It didn’t take the refugees long to figure out how to leverage this to their advantage. “They’ll stand right there, balding, grey at the temples, and insist that they’re eighteen,” an exasperated Austrian prosecutor told me. Having “lost” their documents, the only way to refute even the most patently absurd such claim is through expensive lab tests. If you have no documents and no shame, you can assert just about anything and then lean back and wait for the system to try and prove otherwise. If you are rejected, no problem: you can launch multiple appeals. Once you have set foot in Europe, it will be almost impossible to get rid of you; indeed, you can literally commit murder. If a court finds you guilty of rape, you need only argue that if you are sent home, your conservative society will kill you for the dishonorable act—then you can’t be shipped out, because EU law forbids extradition if doing so puts the individual’s life at risk. And murderers cannot be sent back to countries that have the death penalty or a judicial system known to be harsh.

But we are still left with a mystery. Welfare fraud is one thing: it makes a certain kind of sense, if you have no regard for rule of law or fairness and you are lazy. But why is this current cohort of Afghans making its mark as sexual predators . . . and inept, stupid ones at that? In search of an answer, perhaps we should take a closer look at the victims. We have eliminated improper attire and an unwittingly seductive manner, but might they have any other traits in common to shed light on why they became the targets of such madness? Reviewing them, one word comes to mind: fulfillment. A Turkish exchange student, happy to be advancing her education in industrial design at a good university in Vienna. A girl in a park, enjoying the sunshine. Two friends, taking their babies for a walk. A mother, enjoying a summer stroll with her two children. A contented old lady, out with her pet. Attractive, accomplished, happy, normal people . . . an unbearable sight, perhaps, to—and here I must agree with President Trump—losers. That is what he proposed we should call terrorists, and he is right. These young men, even minus a suicide vest, are losers, which has inspired them to become social terrorists.

The young Afghan attackers are saying, yes, that they have no impulse control, that their hormones are raging, and that they hate themselves and the world—but most especially, that they will not tolerate women who are happy, confident and feeling safe in public spaces. They are saying that they have no intention of respecting law, custom, public opinion, local values or common decency, all of which they hate so much that they are ready to put their own lives, their constructive futures and their freedom on the line for the satisfaction of inflicting damage.

Established middle-class diaspora Afghans are understandably upset and embarrassed to see their nationality thus disgraced by these uncouth newcomers. And yet they are part of the problem. Many of their actions and reactions, however natural or unintended, amount to complicity. They cover up, make excuses for, advise on best ways to wriggle out of consequences, and even directly abet the deceptions, illegal acts and disgraceful manners of friends, relatives and random unknown fellow Afghans.

The reasons for this are many-layered. There is the perceived obligation to be loyal to friends and relatives and countrymen. I think there is also a certain lack of true identification with Western notions of bureaucratic and biographic fact; many, if not most, Afghans currently living in the West have some lies of necessity in their past. Whichever of them arrived first—a father, an older brother—generally had to make up a supposed family name and a birthdate on the fly, because back home, until one generation ago most people did not have a last name and birth dates were not recorded. I know respectable, law-abiding Afghan families where everyone’s birthdays are implausibly sequential—June 1, June 2, June 3 and so forth, because the family member who filled out the immigration paperwork had to make up birth dates and thought it would be easier to remember them this way.

It is also possible that this diaspora community, given the weakness of state institutions in their country of origin, the arbitrariness of its corruption-riddled administrations for centuries, and a certain lack of rootedness that comes from being dropped into someone else’s culture and way of doing things, is fine with a bit of finagling of welfare benefits. They don’t, of course, endorse rape, but here embarrassment kicks in and inspires them to make excuses. “They’re young.” “They’re confused.” “They grew up in Iran, where one learns bad behavior.” Others just disavow them altogether and want nothing to do with them. That’s regrettable, because Afghans who have already made respected lives for themselves abroad are in the best position to discipline and teach the delinquent newcomers, to know what combination of sanctions, pressures and encouragement will be effective.

Complicated problems, to be sure, but why should they concern us here in the United States, beyond mere anthropological curiosity? Well, first of all, these young men are “ours.” They grew up during the years in which we were the dominant influence and paymaster in Afghan society. Since 2001, we have spent billions on an Afghan school system that we like to cite as one of our greatest accomplishments. These young men either attended these schools, in which case the investment in their education has been worse than useless, or did not have access to a school, in which case the money must have been fraudulently diverted. We have also invested many, many millions of dollars on gender programs and rule-of-law programs to convey notions of female equality and human value, and regard for law and order. We have funded radio programs and entire TV stations devoted to this goal, launched poster campaigns and sponsored at enormous cost a large number of civil-society groups purporting to disseminate these values. And here, now, are our “graduates,” rampaging across Europe like the worst sort of feral beasts.

Secondly, the relevance to U.S. refugee policy is sadly obvious. It will require rigorous vetting indeed to weed out such deeply disturbed, degenerate young males whose willingness to be deceptive is so pronounced and whose motives are so irrational.

Which brings me to a final theory being vented in Austria: that these destructive, crazed young men are being intentionally infiltrated into western Europe to wreak havoc: to take away the freedom and security of women; change patterns of behavior; deepen the rifts between liberals, who continue to defend and find excuses, and a right wing that calls for harsh measures and violent responses; to inflict high costs and aggravation on courts and judicial systems and generally make a mess of things.

For the record, I am not convinced that there is a deliberate plan behind this, but I do agree that angry and unstable young men are susceptible to destructive paths. Those paths can lead to ideological extremism and terrorism, or to the formation of gangs and packs that attack, harm and destroy. As we have seen, presently many of their attacks are inept and easily blocked by random civilian passersby. But they will get more skillful over time, and Europe had best develop a defense against them.

What to do? The necessary measures, I think, are obvious.

Anyone convicted of a felony or any kind of sexual crime should be immediately deported, and that consequence should be made known to new arrivals as part of their initial orientation. This is the only way to stop the accelerating problem. (Doing so will, of course, require changes to European law.)

Every arriving refugee and asylum seeker must be subjected to rigorous fact-checking of their story, including validation of their asserted age by lab testing if there is any doubt. Yes, it’s troublesome and costly, but not nearly as troublesome and costly as letting the wrong people in, or putting hundreds of thousands of foreigners permanently or semipermanently on the dole with benefits they are not entitled to. And European countries must share the resultant data with each other, and identities must be linked to fingerprints, not to documents of dubious authenticity or no documents at all.

Members of the relevant diaspora communities must make very clear to the refugees that they do not approve of and will not assist them with their false claims, cheating, bad behavior or crime. They should instead emphasize by their own example, as well as by direct outreach, that a good and fulfilling life is possible in their new homes with hard work, a sincere effort to fit in and a cooperative attitude.

Finally, the Left has to do a bit of hard thinking. It’s fine to be warm, fuzzy and sentimental about strangers arriving on your shores, but let’s also spare some warm, fuzzy and sentimental thoughts for our own values, freedoms and lifestyle. Girls and women should continue to feel safe in public spaces, be able to attend festivals, wear clothing appropriate to the weather and their own liking, travel on trains, go to the park, walk their dogs and live their lives. This is a wonderful Western achievement, and one that is worth defending.

Dr. Cheryl Benard was program director of the Initiative for Middle Eastern Youth and the Alternative Strategies Initiative within the RAND Corporation’s National Security Research Division. Her publications include Civil Democratic Islam, Building Moderate Muslim Networks, The Muslim World After 9-11, The Battle Behind the Wire - US Prisoner and Detainee Operations, and Eurojihad - Patterns of Islamist Radicalization and Terrorism in Europe. Civil Democratic Islam was one of the books found in Osama Bin Laden’s library during the raid on his compound.

Image: Migrants and refugees beg Macedonian policemen to allow passage to cross the border from Greece into Macedonia during a rainstorm, near the Greek village of Idomeni, September 10, 2015. REUTERS/Yannis Behrakis/File Photo​