San Diego — For many years New York led the nation in crime. We boasted the highest rates of serious felonies. Toronto would record 30 homicides a year; New York, 2000. Public buildings looked like something creepy out of Batman's Gotham: dark and brooding. Traffic lights near highway ramps were the turf of squeegee-men, who would clean your windshield whether you wanted them to or not and then aggressively demand payment for their labors. High school kids would swarm curbside grocers and pilfer fruit or raid open-air vendors' merchandise. Street crime flourished, burglaries rose. My brownstone apartment in Chelsea was robbed four times, the last time while my wife was home, nursing our four-week-old daughter. A native New Yorker, she negotiated for items of sentimental value, refusing to have them stolen. Seeing as how her husband was a Vietnam vet, they agreed to bypass my wedding ring. They took some silver dessert knives instead. No problem.

Just outside, in our enclosed back garden, you could take tea and listen to local drug dealers exchange gunfire with business rivals. Early on Christmas Eve, my aged mother and I witnessed them in a local all-night diner, admiring one another's new 9mm Glock automatics, which then retailed for around $4000 apiece. On the police force, only the commissioner possessed a Glock. Street cops, it was argued, shouldn't carry such lethal calibers for fear of wounding innocents. The local card and wrapping paper shop on Ninth Avenue was held up by a shotgun-wielding gunman. The next day he came back and did it again.

Citizens started carrying pistols. In one infamous incident in the subway, some youths with screwdrivers were shot by a fellow passenger they'd approached in a menacing way. Mean streets, indeed. New Yorkers generally accepted that this was the way things were, and they were not going to change.

For years any contact with the world outside your apartment had a component of dread anticipation. People were defensive, snappish, quick to get in your face about nothing. "You gotta problem with that?" became the trademark New York rejoinder. Everyone was potentially armed and dangerous. Locals developed a stare that took in nothing, offended no one, and warned off anyone contemplating an approach.

Navigating the city was an art. You knew which streets and subway stations to avoid and when. What subway lines not to ride at what hours. The danger went with the territory. It was the price we paid for the excitement, the density, the diversity, the edge, and the unspeakable, indescribable energy that never stopped. It was like living in an engine. The rest of the world operated in slow motion.

Then came a new policing philosophy applied by a new commissioner (recently hired by L.A.). Essentially it consisted of the radical idea that cops should go where the crime was. Sites of felonies were flooded with detectives and officers, coordinated from police trailers brought in to direct the campaigns. Squeegee-men were busted. Turnstile-hoppers were arrested. Precinct chiefs were mercilessly grilled and held accountable. Police were armed with new 9mm automatics. It worked. Crime declined. (The economy was also improving, which certainly didn't hurt.) The statistics plunged, the city blossomed. New York became ebullient, prosperous, safe.

The computer revolution drove Wall Street to unprecedented heights. New York was the capital of capital. Times Square was deloused and developed into a theme park, landmark buildings cleaned and illuminated. Real estate, hotels, art, advertising, fashion, restaurants, even poetry -- everything flourished. The town shone.

Then Wall Street crashed and the dot-com bubble burst. Shortly afterward, terrorists took down "David" and "John," the downtown towers nicknamed for the Rockefeller brothers whose influence had imposed them, over serious objections, on the New York skyline. They brought the towers down on the day their colleague was being sentenced a few blocks away to life plus 240 years for an attack on the same towers eight years earlier. The courthouse was heavily guarded: police had braced for trouble, but no one had anticipated anything on that scale. Gloom descended. So did a new anxiety that replaced the edgy jitteriness of old. Crime remained down but worry soared. As various safety schemes and measures were made public, it became obvious that everyone was again on his own. And this time there were no unwritten rules to follow, no understandings. There were no bad streets you could avoid, no situations you could circumvent in relative safety. The whole city was up for grabs, a target of opportunity. Nowhere was safe, not even your house.

New Yorkers hate to admit it, but they're scared. For all the show of force -- troops in the train stations and subways and museums, heavily armed cops in Times Square and outside St. Patrick's Cathedral -- they know. If it's going to happen, it's going to happen. None of the countermeasures is likely to stop an attack. All the New Yorker has on his side are the percentages.

Some, like my brother-in-law, try to hedge their bets. He is an engineer, successful, organized, calm. Wherever he goes, his attaché case contains a flashlight, work gloves, protective goggles, a crowbar, and a particulate mask. Another friend has stopped taking the subway, generally thought to be a prime target. She takes buses, leaving hours earlier because they're slow. And she carries her $75 gas mask; her kids and husband refuse theirs and continue to use the underground system.

My office is 4.9 miles from my front door in Brooklyn, where we've lived for four years. I know the distance exactly because I used to commute by bicycle until I had to stop for medical reasons. So I take the subway to my office just off 14th Street near Union Square. Where I once looked out for aging gangbangers and indigent lunatics, I now look out for I don't know what. It's not a comfortable commute, although it's mercifully short.

As I walk along Flatbush Avenue, nine helicopters fly overhead in formation, making a sound as familiar as my heartbeat. Once it quickened the pulse, now it just brings worry. At least no gun barrels protrude from them. I exhale and march on to the station at Atlantic Avenue. Around the corner from the entrance, near the flag-waving post office, is the Al Farooq mosque, one of whose clerics the Justice Department alleges collected $10 million there for al-Qaeda. Neighboring Muslim businesses sell Arab dry goods, foods, and garb: djellabahs, hijabs, chadors. Also soap and religious books on Islam and on Islam and Christianity. Some of the shops once displayed odd posters. When I asked for translations, the shopkeepers would shrug off the requests. The impression I got was that they were critical or even outright anti-American. These days they're no longer in evidence.

Downstairs, just beyond the toll booth, stand three soldiers in black berets and camouflage fatigues. One has his assault rifle slung on his shoulder, a new edition of the M-16 I carried. The other two stand with weapons at the ready, hands on the grips, fingers near the triggers. Their black guns will fire the 20-round magazine in under two seconds, making toys of even the 9mm automatic handguns the police carry. I can't imagine what such firepower would sound like in a confined concrete space like this or the damage it would do to anyone in the way of the shots or ricochets off the stone and tiles. What training could they possibly have had in subway shootouts? None, I'm sure. But the station, the target of a foiled bomb plot several years back, is the hub for six different subway lines and a terminus for a Long Island Railroad branch. So it's strategic and heavily trafficked. Like my destination.

I board the W express for the 15-minute, two-stop run to Union Square. Its route takes us across the East River on the Manhattan Bridge. As we roll outside into daylight, the financial district's skyline comes into view. Immediately south, parallel to us, is the majestic Brooklyn Bridge. An iconic target by all accounts. The police are checking cars and vans. On a raised walkway running down its middle, pedestrians stride along, sharing the elevated boardwalk with cyclists.

In the subway car cell phones pop open and antennas are pulled out like cotter pins. Quick calls are squeezed in before the train dives back underground on the far side. The express stops at Canal Street in Chinatown. A slash of graffiti reads "MAKE FUCK NOT KILL."

The train pulls out and speeds uptown on a straight line for 14th Street. A few weeks ago an art student placed black boxes labeled FEAR throughout the station as part of a public art project. The police went into full defensive mode. That day my train, instead of stopping, sped right through the deserted station without warning. When I trekked back to 14th Street and Broadway, the square above the station was flooded with patrol cars, bomb-squad vans, bomb-sniffing dogs, and a small army of uniformed police and detectives.

Even without the errant art, most mornings police abound. With seven subway lines crossing at the station, the police take every precaution. This morning, aboveground, the free-speech tradition of the square has drawn antiwar activists again. Speakers address the crowd from the steps of an equestrian statue of George Washington. At a more creative moment the demonstrators will all "die," falling to the ground in solidarity with civilians dying elsewhere at American hands. MTV interviewers stand over them with mikes, the hoods of their sweatshirts drawn up against the chill rain that's begun. The lights bleach the damp air. "YEE-HAA IS NOT A FOREIGN POLICY" reads one sign. "DRAFT THE TWINS, NOT THE POOR" says another.

This is a major issue on MTV, the inequities of the defunct draft and of the makeup of today's volunteer military. Of the 535 federal legislators in Washington, it seems that only the senator from South Dakota has a son in the service. Shades of Vietnam. Watching the Super Bowl, I laughed out loud at the shameless hypocrisy of the NFL juxtaposing itself with servicemen and women, pilots, planes, rockets, and flags, evidencing their support of our brave boys and girls about to take on Saddam. In ten years of fighting in Indochina, exactly one professional athlete ever carried anything more dangerous than an autographing pen, and he was only there because he had screwed up his reserve status.

The police have cordoned off the youthful demonstrators with aluminum barriers and stand behind them patiently. Nearby a life-sized bronze statue of Gandhi catches him in mid stride. Often, he wears a garland of fresh marigolds. And some days the Mahatma is sandbagged.