One in five Swiss residents was born somewhere else. The indigenous citizens never asked for and weren’t consulted about such a transformation of their society, it just happened thanks to the usual mix of unrestrained immigration and political correctness. All along, Switzerland has remained one of the more difficult countries for an immigrant to become a full-fledged citizen. But a recent effort to relax the standards for attaining citizenship was recently beaten back by the Swiss People’s Party, which rules from the right and is set to win this month’s elections. The Swiss People’s Party (SVP) has become the leading force trying to curb immigration to Switzerland, and has taken to producing political posters that most Americans would probably find distasteful if not obviously racist. Behind all of this is a reasonable fear of the rise of radical Islam in Switzerland; the SVP has campaigned against allowing the building of minarets. And its appeal to preserve Switzerland has made it the most popular party in government.

You need all that background to understand the next two vignettes. The first is the most recent. The Swiss People’s Party was trying to hold a political rally in Bern on Saturday. It didn’t go smoothly.

The Swiss capital of Berne was turned into a battle zone at the weekend when leftwing radicals seized control of the main square outside parliament, routing the main far-right political party two weeks before a general election and catching the Swiss police off guard.

Dozens of protesters were arrested and around two dozen people injured, mostly police officers, as police deployed tear gas, water cannon, and rubber bullets to try to regain control from gangs of highly organised, masked people who turned the small and normally sleepy capital of Switzerland into a scene of devastation.

The clashes on Saturday and the revulsion triggered among mainstream Swiss by the unusual street violence are likely to play into the hands of Christoph Blocher, the tough-talking populist and millionaire industrialist who leads the Swiss People’s Party (SVP), the far-right movement tipped to win the elections later this month following a campaign denounced as overtly racist by a United Nations watchdog.

Mr Blocher called a campaign rally of his party in the capital and some 10,000 of his supporters converged on Berne to march to the capital’s main square in front of parliament.

But the planned rally was hijacked by up to 1,000 masked street fighters who blocked the SVP’s progress, outwitted the police by operating in small groups moving in and out of the crowds, and ransacked the SVP stage and campaign equipment.

The Federal Square, site of a charming Saturday morning flower and vegetable market, resembled a war zone by Saturday night, littered with debris, masonry, shattered glass and torched metal.

The city mayor admitted “impotence” in the face of the riots. The trouble raised questions about the readiness of the Swiss authorities to cope with potential hooliganism at next summer’s Euro 2008 football championship being hosted jointly by Austria and Switzerland.

It calls a great deal more than the viability of a soccer tournament into question. Vigilantism on both sides seems to be on the upswing.

ZURICH — At 1:30 a.m., Antonio da Costa heard a knock at the back entrance of the McDonald’s restaurant where he worked as a janitor after-hours.

He opened the door, he recalled in an interview. There stood two men, each gripping a chain saw. One yanked the cord on his saw, stepped toward da Costa and shouted above the roaring machine: “We don’t need Africans in our country. We’re here to kill you!”

The two masked assailants cornered da Costa and began raking him with the whirring chain-saw blades. They slashed one arm to the bone, nearly sliced off his left thumb and hacked his face, neck and chest, the 37-year-old Angolan said, his voice quavering as he recounted the May 1 attack.

The gruesome assault in a suburb of Zurich — consistently ranked in international surveys as one of the world’s most livable cities — dramatized the surge in racism and xenophobia as Switzerland confronts its most difficult social transformation in modern times. Today, more than one in five people living in Switzerland are foreign-born, the second-highest percentage among countries in Europe.

One of the world’s oldest democracies is at the center of Western Europe’s most divisive political debate: to embrace an increasingly globalized, multicultural society or to retreat into social isolation in an effort to preserve eroding traditional identities.

Mixed in with that very real horror that leads the story is the press’ typical way of framing the issue: Those who oppose unrestrained immigration from societies with no history of democracy are called “racists” and “xenophobes” without ever looking into what they’re actually objecting to or whether they might have a point. For its part, the UN just waltzes in, describes the SVP as racists as the press slings around Nazi analogies, and considers its work done. Politicians aren’t critically examined for the roles they may have played in creating the situation or making it worse. Politicians who favor the situation are likely to frame things in the same way, which will only lead to frustration and more lashing out — on both sides. The possibility of honest dialogue evaporates. The result is likely to be a society in which fewer and fewer actually think that the press is honest or that the politicians will actually do anything useful about the situation that they have created, which will probably lead to yet more vigilante and street violence.

I’m not justifying any of it, on either side. The attack by the men with the chainsaw was brutal, cowardly, wrong and monstrous. What the left-wing rioters are doing rips at the heart of the country’s ability to find a peaceable way out of the mess. So I am observing that if the situation isn’t addressed, it may tear Switzerland apart. Countries across Europe face the same issues that Switzerland is facing, of non-assimilation and increasing intolerance from Islamic radicals thanks to the unrestrained immigration that they all allowed over the past few decades. The next few years and decades will determine what kind of Europe survives the transformation that most of its citizens never asked for.

Some Europeans are awakening to the danger. But are enough?

(Language alert)