It’s a plague.What erupted in the 1990s with the rise of 10-foot metal walls between the houses of San Diego and Tijuana, running through the two’s shared beach and into the ocean beyond it, has since spread to three more continents and is now mushrooming even more intensely, epitomizing what is clearly a new and foreboding zeitgeist.The seaside partition that was followed by 700 disjointed miles of American barriers was joined by African partitions, as Spain surrounded its north-Moroccan enclaves with walls, fences and barbed wires, after Morocco itself stretched a 2,700-km. sand wall along its southern and eastern border, and planted alongside that obstacle the world’s longest minefield.In Asia, Israel built a 240-km. fence along its Egyptian border, not long after having completed the famous West Bank fence, not too long before Turkey announced two weeks ago that it plans to build a 700- km. fence along its Syrian border. Construction of Saudi Arabia’s 1,000-km., five-layered continuum of fences, ditches, watchtowers, radars and cameras alongun its border with Iraq is already under way.Meanwhile, on Turkey’s other end, Bulgaria is building a 160-km. fence along its Turkish border. And just to that border’s south, Greece is preparing to build a wall along its 200-km. border with Turkey. And deeper into Europe, Hungarian soldiers last month began stretching a 160-km. fence, 13 feet tall, between their country and Serbia.Such, then, is the world into which humanity is now marching, a world where thousands of floodlighting border patrols snake their way night after night, where hounds bark at people day after day along partitions of steel and cement crowned with barbed wire, adorned by infrared cameras, and checkered with ultrasensitive sensors under buzzing drones.It was only yesterday that the Berlin Wall crumbled, border checkpoints vanished, visa requirements diminished, and globalization made the world so borderless that American conveyor belts migrated to China, Russian basketball players joined the NBA, Japanese brokers sold Brazilian bonds, and Chinese workers emerged on Israeli scaffoldings.Now, 25 years after its arrival amid a universal sense of epiphany, the age of falling borders is drawing to a close, making way for an era of closing borders, rising partitions and shutting doors. A brief age of optimism has given way to an age of walls.How did this happen to us, where is all this headed, and what does this transition mean? THE ERA OF WALLS was ushered in by fundamentalist terrorism and illegal migration.Morocco’s, Saudi Arabia’s and the West Bank’s fences were designed to block Polisario’s, Islamic State’s and Hamas’s terrorists. Among the era’s physical walls these are the exceptions, as most are not about terrorism, yet the era’s partitions are not only those that snake physically along borders.What slices deserts, mountains and beaches continues in the world’s airports.With the previous era’s carefree travel a fuzzy memory, millions line up at any given moment en route to metal detectors where they are scrutinized along with their belongings, children, babies and grandparents before being frisked shoeless, and after a uniformed custodian of the age of walls sifts studiously through their passports and, once finally raising her suspicious eyes from the little booklet, commands: “Look at me!” True, our era’s multiplying physical walls are mostly not about terrorism, but about blocking usually innocent people out to eke a living in countries that offer all the wealth, freedom and opportunity that their own countries quell.In fact, our era’s walls are the inversion of the Cold War’s fences; instead of blocking escapees, as the Berlin Wall did, ours challenge infiltrators. This irony is particularly striking in the new Bulgarian fence, which runs exactly where a similar barrier marked the former East Bloc’s border with the outer world, before it was happily and festively uprooted the morning the Cold War ended.Now happiness is gone. Like Israel, whose Egyptian fence blocked an influx of African immigrants, the US is spending billions blocking Mexican migrants, while Turkey is fending off Syrians and Europe faces a convergence of Arabs, Africans and even Afghans.Surely, from boatloads of Somalis capsizing between Libya and Sicily, to Eritreans braving tear gas in the train tunnels between Calais and Dover, the migration pressure Europe faces is immense. Yet the trends at play run deeper than migration.Just as Israel’s fences symbolized the collapse of its New Middle East dream, Europe’s mark the demise of its United Europe vision.There will be more fences in upcoming years, some physical, some legal, and some commercial, and this is besides the mental and emotional walls which are already erect in a growing number of places, and which will be even thicker than our era’s physical walls.THE AGE OF WALLS, in its resolve to ruin the previous era’s tools of harmony and symbols of fraternity, has already marked its next target – the euro.The currency that was invented in order to prove that what unites people is stronger than what divides them, has itself become an engine if division, sending to the streets thousands who now deride this well-intended financial invention as what robbed them of their jobs, property, dignity and hope.Such is also the fate of globalization, the previous era’s main article of faith and now a fallen idol, universally condemned as immoral, impractical, unaffordable and the most potent threat to global justice, stability, harmony and peace.Violence, first within and then between countries, is clearly on its way. It has already begun.Along the borders, what has so far been passive killing, like the several hundred Mexicans who die annually of exposure while trying to ignore the era’s walls, or the thousands who drown while trying to cross the Mediterranean, has already become active killing in some cases. In 2005, for instance, six African migrants were shot dead while climbing the fence of Melilla in Spanish Morocco, and at least 12 were killed and 50 were injured by border police while trying to scale the walls of Ceuta, another African patch of Spain’s.A hint of the violence the world is in for slipped the other day off the tongue of British Prime Minister David Cameron, who called “swarms” the thousands of illegal migrants now staring in Britain’s eyes when it looks through the Chunnel.Critics who attacked Cameron’s choice of words may for a while temper political rhetoric, but they won’t reverse the growing sense of impatience that most Brits now share and their prime minister voiced, and they will not lower, let alone remove, any of the era’s proliferating walls.In the era that is upon us borders will continue to tighten, hearts to stiffen, and minds to darken. In due course border patrols will shoot with growing frequency while jihadist terrorism will hammer at civilization with growing audacity until jobless mobs, like those who are already torching mosques in Sweden, increasingly attack stores, schools and shrines of those they will see as their invaders, robbers and killers.So grotesque is the aftermath of the previous age’s gospel of a borderless humanity that the new era’s prophet of borderless salvation is this ideal’s great perversion, Islamic State.Now, in the spirit of the fundamentalists’ medieval mindset, the world that only yesterday was as open as ancient Rome will gradually return to what feudal Europe was, a truncated ruggedness of isolated fortresses inhabited by introverted landlords and topped by pacing, suspicious and trigger-happy sentries.LAST WEEK, as the Ninth of Av’s dusk replaced its daytime’s punishing heat, I climbed the bridge above Jerusalem’s Cinematheque and surveyed the view – from where Roman troops once built the dike with which they doubled Jerusalem’s siege, to where Middle Israel built the wall that stemmed terror’s assault.It had been 11 years since I wrote of the newly sprouted wall that it marked the end of an era; an Israeli era; the era when Middle Israel, recalling how in 1967 it felled Jerusalem’s walls and welded its estranged halves, set out to eradicate the rest of the region’s partitions and produce a New Middle East. Looking at the young wall I conceded wryly that Middle Israelis “are building a wall to their east and looking to their west.”A decade on, looking to our west is no longer any consolation, as the entire world is becoming a thicket of physical, legal and mental walls, as if God descended on the visionaries of globalization, United Europe and the New Middle East, and convicted them of rebuilding the Tower of Babel.