By MARC LACEY TIJUANA,

Mexico - Never a particularly pretty place, the border is at its ugliest right now, with violence, tensions and temperatures all on high. Once thought of by Americans as just a naughty playland, the divide between the United States and Mexico is now most associated with drug gangs brutalizing each other, tourists getting caught in the cross-fire, and Mexican laborers braving heat and bullets to cross the desert northward .


Meanwhile, National Guard troops are preparing to fill in as border sentries. All these developments are unfolding in what used to be a meeting place between two countries, a zone of escape where cultures merged, albeit often amid copious amounts of tequila. The potential casualties at the border now include a way of life, generations old, well-documented but decaying by the day. The 3,000-kilometer stretch has long been a netherworld crossed by Americans in search of forbidden pleasures as much as by Mexicans desperate for work.

It is an area neither completely Mexico nor completely El Norte. And a dollop of danger, a quest for sin, was always part of its charm. The modern story begins with Prohibition, when Mexico became the place for thirsty Americans to go for a cheap, legal drink. Over the years, the lure of cheap booze gave way to quickie divorces, dog races, strip shows, slot machines and brothels where fathers sometimes brought their sons . Through it all, there were plenty of drugs ? medicinal as well as illegal .

World War II only boosted the market for a generation of soldiers on leave, and for postwar adventurers seeking music and thrills and sex. In the 1960s, Mexico firmly solidified its place as America’s marijuana and heroin provider. As commerce ? licit and illicit ? grew, politicians and police protected it. But the rules of engagement that once protected innocents eventually began to break down. Nowadays, anything goes.

In 1958, Orson Welles used the border as backdrop for his classic noir film “Touch of Evil.” And in the 1990s, Cormac McCarthy set his trilogy of “Border” novels there as well, infusing his writing with adventurous tales and tragic love affairs. But little that any of the writers or filmmakers came up with rivals today’s real-life spate of killings by men with no compunction about pulling the triggers on their automatic rifles as their drug gangs defy the authorities and fight for pre-eminence.

The naughtiness that used to give the border its flair seems innocent now. The prostitutes, hustlers and con men who once had free rein are, like everyone else, scared out of their wits. The easy smiles of Mexican border guards, welcoming free-spending tourists, are giving way to fences and armed American soldiers. And as this happens, longtime lovers of the border fear most for the backand- forth itself - for the interchange, even if asymmetrical and exploitive, of poorer Mexicans and free-spending Americans that over the generations has, to some degree, fostered understanding between the two countries.

“The relationship that once existed between the two sides is broken,” lamented Luis Ituarte, who splits his time between Los Angeles, where he promotes the arts, and Tijuana, where he runs a cultural center. “There used to be so much mixing. Young people in San Diego would go for the night to Mexico. As a young boy in Tijuana, a night out in San Diego was something I did all the time. You got to know people on the other side.

” As the violence rises, tourism has flagged all along the border. The latest State Department travel warning from the United States speaks of “large firefights” in broad daylight . Juarez and Tijuana, it notes, have been particularly deadly places for Americans. Friendship Park once connected San Diego and Tijuana and allowed residents on both sides to picnic together. It now is bisected by barriers that keep Mexicans and Americans well away from any contact.

Not all is dire. The big-name international brands that operate maquiladora factories continue to operate . And one can still find some art museums, fancy business districts and upscale housing developments along the border. But as I cross back and forth at some of the border’s most troubled points, I find that even a journalist faces scrutiny . “You sure you want to go down there?” an American inspector said to me recently


Police examine the bodies of men slain in Ciudad Juárez, Mexico.