海角大神

To Georgina Rios and her family, it was always la l铆nea, the line. Her mother and grandmother were born on one side, and she was born on the other, in Nogales, Ariz. It was the 1950s, and the family鈥檚 rustic bungalow had sweeping views of Nogales, Mexico, which unfurled south of the simple chain-link fence that marked the international border.听

Ms. Rios, not yet 10 years old, would come home from school to find her parents, grandparents, and neighbors drinking coffee and chatting with friends from the other side of la l铆nea. A Mexican vendor carrying a basket full of freshly baked bread on his head would pass loaves to customers through gaps in the border fence. Nobody in the neighborhood worried about locking doors.

Today Nogales鈥檚 chain-link fence is only seen on vintage postcards. In the mid-1990s, a metal wall rose in its place; in 2011 came an $11.6 million bollard-style barrier supplemented by surveillance cameras, stadium-bright lights, and the ever-present green-and-white patrol cars of US immigration officials. 鈥淚t鈥檚 a different era now,鈥� says Rios.听

Half a world away in Hungary, another border wall is rising: a 13-foot-high steel frame covered with chain-link fencing. At the top and bottom are coils of razor wire. The imposing wall cuts through picturesque farmland, running alongside fields of grapevines, sunflowers, and corn.听

On the other side are Hungary鈥檚 neighbors, Serbia and Croatia. Like Hungary, they have become transit routes for hundreds of thousands of people fleeing wars in Syria, Iraq, and Afghanistan and seeking refuge in Europe. Hungary鈥檚 340 miles of fencing is there to keep them out.听

鈥淲e passed all these obstacles, we overcame death and fear, and arrived here to find a steel wall,鈥� says Mohamed Shaker, a young man from Syria who is standing near a barrier at the official crossing from Serbia. 鈥淲hat will we do now? I don鈥檛 know.鈥�

Building fortified barriers to repel and deter outsiders is an ancient practice rooted in military strategy, from China鈥檚 Great Wall to the Maginot Line that France created to defend itself from German aggression. Walls are also a way for rulers to define their states and to assert the hard edge of their authority. In AD 122, the Roman emperor Hadrian ordered the construction of a 73-mile stone wall across the breadth of northern Britain. Hadrian鈥檚 Wall would be the empire鈥檚 northwest frontier for nearly 300 years, a symbol of its political might.听

Today鈥檚 wall builders aren鈥檛 fortifying borders to stop armored columns or armies on horseback. Their targets are primarily migrants: people seeking to move from one country to another, driven by fear or drawn by opportunity. Their construction speaks to an era of insecurity, a walled-in world in which the fault lines are political and economic.听

The ideological contests of the cold war are over. But globalization hasn鈥檛 delivered on its promise of seamless mobility and shared prosperity. Not long ago, theorists argued that the nation-state and its borders were vanishing: From now on, global consumers, and the companies that served them, would set the rules.

Instead, this unhindered flow of capital, ideas, goods, and people 鈥� melded with fears of global terrorism 鈥� has in many ways ushered in a hardening of national boundaries, a razor-wired riposte to the footloose. The world is experiencing a sober awakening of state sovereignty in the form of a new era of barricaded borders.

鈥淎fter 20 years of talking about globalization and a borderless world ... ever since 9/11 and particularly in the last year or two, borders have come back in a very big way,鈥� says David Newman, professor of geopolitics at the University of Ben-Gurion of the Negev in Israel. 鈥淭he idea of a world without borders is a fickle one.鈥澨�

A new study by two political scientists at the University of California, Berkeley found that half of all international border fortifications built since the end of World War II 鈥� 25 out of 51 鈥� were started in the past 15 years. And those numbers were compiled before Europe鈥檚 refugee crisis erupted last summer. Wall-building is flourishing, says Ron Hassner, an associate professor at UC Berkeley, and countries are 鈥渘ot interested in open borders and merging鈥� into their neighbors.

His study and a similar research paper by scholars at Princeton University found that the most likely reason that a state erects a border wall against its neighbor isn鈥檛 armed conflict or territorial disputes. It is economic disparities. Rich nations are sealing off boundaries with poorer nations 鈥� and specifically with nations where poor people are on the move.

As wars in Syria, Afghanistan, and elsewhere displace record numbers of people, the movement of migrants is unlikely to abate. The United Nations鈥� refugee agency said in June that 59.5 million people 鈥� 1 person out of every 122 on the planet 鈥� had now fled their home and sought refuge either within their own country or abroad. 鈥淭his is a trend, not a blip,鈥� says David Miliband, executive director of the International Rescue Committee in New York.听

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in 221 BC, Qin Shihuang defeated a series of rival rulers to become China鈥檚 first emperor. He ordered that all weights and measures be standardized, and created a national currency. He decreed a unified system for Chinese characters. He burned piles of books, from poetry to philosophy, and executed those who didn鈥檛 accede to his demands. 听

Then he began to build a wall.听

The Qin wall would stretch some 3,000 miles across China, a barrier against nomadic invaders from the northern plains. In time, it would become a fount of myth and mythmaking, an enduring metaphor of ambition and secrecy.

To this day, foreigners continue to marvel at China鈥檚 Great Wall (which actually is a series of walls, built in different eras, that were never a unified structure). During a visit in 2013, Israeli Prime Minister Benjamin Netanyahu said, 鈥淛ust like the Chinese defended themselves by locking themselves behind a great wall, we, too, will continue to do so in a similar manner on ... all the fronts we face.鈥澨�

But the question is, Do walls actually work 鈥� do they prevent the wrong people from crossing into a country? And, if so, what are the consequences of that reduced flow, intended or not?听

Measuring the effectiveness of border barriers is tricky. Even the Great Wall of China still inspires debate. Some military historians argue that the elaborate Ming fortifications failed to repel raiders and were mostly the work of weak rulers who overspent on defense and fumbled on diplomacy.听

But David Spindler, a scholar who has walked much of the wall鈥檚 length, disagrees. True, some Mongol raids during the 15th and 16th centuries succeeded in breaching the barrier, with bloody consequences. But others failed, and, in the end, the Ming Dynasty endured until 1644. 鈥淸The wall] worked well at times. It depended how well it was defended,鈥� Mr. Spindler says.听

Judging the usefulness of walls today is even more difficult, given that the gauge of success isn鈥檛 an invasion repelled but more ephemeral benchmarks: the flow of migrants curtailed and the amount of contraband stopped. And many governments are reluctant to share data on illegal migration. Some also inflate external threats in order to justify their walls and fences.

鈥淭he security argument buys in a lot more people than an economic argument,鈥� says Mr. Newman, who studies border policies and ethnic-territorial disputes.听

It鈥檚 also hard to assess more intangible measures, such as how many illicit crossings would have occurred had a barrier not been erected. Absent such studies, policy debates quickly assume partisan forms: Security hawks trumpet the impact of walls on stopping or detecting infiltrators; critics see them as morally wrong and ineffective, just diverting people to alternative routes.听

In the United States, the debate over borders has been turbocharged by Donald Trump. The GOP presidential aspirant has vowed to build a giant wall along the entire 1,954-mile US-Mexican border. In September, he said that the existing system of barricades 鈥� much of it built since 2006 at a reported cost of more than $7 billion 鈥� is too small and doesn鈥檛 work. He called it a 鈥渏oke.鈥�

Still, fortified barriers can make a difference. They raise the cost of crossing a border 鈥� and make it easier for guards to detect people trying to enter illegally. Israel鈥檚 security barrier around the West Bank, designed to stop Palestinian militants, is a prime example: Suicide bombings dropped after its construction began in 2002. 鈥淭he impact was immediate and visible. It advertised itself,鈥� says Mr. Hassner.听

Israel is not alone. Roiled by war and upheaval, other countries in the Middle East are scrambling to add border fortifications. Hassner notes that Muslim-majority states are responsible for roughly half of all border walls built since 1945, mostly against other Muslim states.听

Across the US-Mexican border, illegal immigration is actually declining. While some credit the fortified barrier with Mexico and more spending on surveillance and border patrols, other analysts say migration tends to track the US economy. Since the 2008-09 recession, far fewer are trying to cross the border. Of those who do, an increasing number aren鈥檛 Mexican job seekers but minors fleeing violence-plagued Central America.听

Border agents detained 487,000 people crossing illegally in fiscal year 2014. That鈥檚 down from a peak of 1.6 million in 2000 after a surge in the 1990s following the signing of the North American Free Trade Agreement by the US, Canada, and Mexico.听

It鈥檚 a period that Rios and her family remember well. Strangers would knock on the door asking permission to drink water from their outdoor faucet. When individuals turned into groups, the family stopped opening the door. Shirts and socks started disappearing from the clothesline, and one day the family鈥檚 Labrador vanished. She was discovered in the basement, alive, along with three bundles of drugs wrapped in plastic, which the family turned over to police. 听

Drug traffickers thwarted by the fortified fence began digging tunnels to transport marijuana and cocaine into rental or abandoned homes. The family eventually moved half a block up the hill, where Rios鈥檚 mother still lives. 鈥淭he value of the homes had dropped significantly,鈥� she says.听

Border crossers don鈥檛 come around much these days. But the drug cartels are still active: A smuggler鈥檚 ultralight aircraft recently dropped a bundle of marijuana onto a carport by accident. The coyotes who smuggle people across the border are also still in business, just rarely in towns like Nogales. And as it became harder to slip over the border, coyotes exacted higher prices and migrants took greater risks along their route. But they didn鈥檛 stop trying to cross la l铆nea. 听

Many believe the crossings are likely to pick up with a stronger US economy, given the wide economic disparities north and south of the border. Peter Andreas, a political scientist and immigration expert at Brown University, believes that border enforcement didn鈥檛 stop migration. 鈥淲hat it did do is change it,鈥� he says. 鈥淚t moved it away from major visible urban centers, out of the public eye, and pushed it into remote, distant, dangerous terrain.鈥澨�

Rios sees the border fence as 鈥渁 double-edged sword,鈥� which she reluctantly accepts. 鈥淲e do need it now because it鈥檚 not the good old days anymore: You do want it for control,鈥� she says. 鈥淏ut at the same time, it鈥檚 a harsh thing to see every time you drive into the neighborhood.鈥�

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On Sept. 6, in the midst of Europe鈥檚 refugee crisis, Sweden鈥檚 prime minister, Stefan L枚fven, addressed a pro-refugee rally. Europeans would not shirk their moral responsibility to help migrants pouring into the Continent, he said. 鈥淲e need to decide right now what kind of Europe we are going to be. My Europe takes in refugees. My Europe doesn鈥檛 build walls.鈥�

A generation ago, Europe tore down the walls and fences that formed the Iron Curtain between West and East. Today, Bulgaria and Hungary are installing border walls manned by armed guards, echoing the barbed-wire demarcation of the Soviet Empire. The irony is compounded by the pivotal role played by Hungary in 1989, when it opened a transit route for East Germans escaping to the West. That year, smiling Hungarian soldiers posed for TV cameras as they used wire cutters to snip the fence between Hungary and Austria. Months later, the iconic Berlin Wall came down without a shot being fired.听

While the tumult of 1989 unfolded on Hungary鈥檚 border with Austria, the spotlight now is on villages such as Asotthalom, a transit route on the border with Serbia for asylum seekers heading north. Since the border fence was completed in September, fewer are coming 鈥� but they still come. Many are bleeding after tangling with the razor wire. Soldiers spend a lot of time repairing the holes that refugees have cut in the fence.听

Many residents seem ambivalent about the barricade. They don鈥檛 really like that it鈥檚 there 鈥� and hunters bemoan that it divides the habitat of the deer and rabbit they liked to shoot 鈥� but they鈥檙e glad to see fewer foreigners. 鈥淭his fence is working, but people don鈥檛 like it,鈥� says Zsolt Revak, a retired butcher with a gray goatee. 鈥淭his is Europe; it鈥檚 not good to have a fence on the border.鈥� On the other hand, he says, 鈥淵ou have to stop [the influx] somehow.鈥澨�

Residents grumble that the fence, built by private contractors under military supervision, enriched cronies of Prime Minister Viktor Orb谩n. Others complain that it鈥檚 not effective and that it would be better to spend the money on improving public services.听

Laszlo Oze, who works in forestry management, says he feels sorry for genuine refugees. But then he repeats reports in pro-government media of terrorists hiding in their midst and claims that some refugees are rich. One was found to be carrying six passports and an expensive watch, he says, citing a news report. They bring deadly diseases, which makes them 鈥渨orse than bin Laden ... who killed people quickly.鈥� He adds: 鈥淭hey are all so dark. I don鈥檛 want to judge, but they look somehow violent.鈥澨�

Hungary, like other former Soviet states, largely missed out on Europe鈥檚 postwar waves of nonwhite immigration from former colonies in Asia and Africa. Eastern European leaders say their societies aren鈥檛 equipped to absorb large numbers of newcomers. And since refugees ultimately want to reach Germany and Sweden, there is no point trying to house them. 听

But behind this rationale for border walls lies an undercurrent of racism and xenophobia, what amounts to an atavistic fear of Muslims whose modern journeys retrace those of the Turkic armies who menaced Christendom鈥檚 eastern frontier. Mr. Orb谩n鈥檚 center-right government has been accused of spreading racist propaganda about migrants. He has invoked the defense of 海角大神 values in turning away Muslims. For its part, Slovakia鈥檚 government has said it will only accept 海角大神 refugees and warned that Arabs pose a security threat.听

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For now, Hungary鈥檚 rollout of razor-wire fencing has succeeded in diverting migrants into neighboring countries like Slovenia and Croatia. But it could be tested by another surge of people. Mr. Miliband, who is a former British foreign secretary, is skeptical of what barricades can achieve amid such pressure. 鈥淗istory shows that increasingly desperate people will get around or under or over fences,鈥� he says.

Unless states are willing to flout humanitarian norms 鈥� as East German soldiers did when the Berlin Wall was breached 鈥� it鈥檚 virtually impossible to keep out the most determined or destitute, says Newman.听

The plight of refugees trying to cross the Mediterranean shows the limits of maritime border policing. Earlier this year, critics condemned the European Union for scaling down an Italian-led operation to retrieve rickety boats abandoned by smugglers. While European leaders rail against the callousness of smugglers who profit from clandestine sailings, the unwelcoming policies of many countries toward refugees are diverting more of the migrants into boats, at higher prices.听 听

In the 1980s, the US faced a similar crisis over waves of Cuban 鈥渂oat people鈥� who were allowed to leave and seek asylum in the US. Then as now, the humanitarian response became tangled in politics: Fidel Castro was accused of seeking political concessions from Washington by making threats to send more refugees into US waters.听

Libya鈥檚 late dictator Muammar Qaddafi also used this tactic, vowing in 2010 to flood Europe with African migrants if it didn鈥檛 prop up his regime.听

Under such circumstances, refugees can become a means of blackmail, showing that border defenses don鈥檛 operate in a political vacuum. Kelly Greenhill, an associate professor at Tufts University in Medford, Mass., studied 70 examples since 1951 of such extortion in her book 鈥淲eapons of Mass Migration: Forced Displacement, Coercion, and Foreign Policy.鈥� It鈥檚 a winning tactic: Many countries succeeded in forcing concessions from other nations. 鈥淭he numbers [of refugees] don鈥檛 have to be large. It鈥檚 not the size, it鈥檚 the expected response of the recipient population,鈥� she says.听

To be sure, migrants aren鈥檛 the only targets of wall builders. Israel has built walls or fences along all its borders. The self-declared Islamic State respects no boundaries, arguing that the caliphate encompasses all Muslim lands, which may force countries in the region to fortify their borders even more.

The world鈥檚 longest-standing border barrier is the 148-mile demilitarized zone that has separated North and South Korea since 1953. It has already outlasted the Soviet Union鈥檚 vast tracts of border fences, and the Berlin Wall that President Reagan urged Moscow to tear down.听

Outside the village of Kubekhaza, Hungary, where the country intersects with Serbia and Romania, the border fence comes to an abrupt end. The village is surrounded by plowed fields of black soil, and a yellow church with a decorative spire rises over a park. Fewer migrants pass this way, but most residents are supportive of the fence and suspicious of foreign faces.

That makes Gyorgy Talaber, a retiree, something of an outlier. He sees the fence as a tactic for Orb谩n鈥檚 ruling party to whip up xenophobia and outflank far-right rivals. 鈥淚 spent 40 years behind a fence during the Communist period,鈥� he says. 鈥淭his fence is against us. It鈥檚 not against the Muslims.鈥� He adds: 鈥淲ho knows what awaits us.... One day all the country will be fenced in.鈥�

With reporting by Lourdes Medrano in Nogales, Ariz., and Kristen Chick in Asotthalom, Hungary