New York Times News of the Week in Review - April 11, 2004 -  BAGHDAD, Iraq -    Just the other day, on the outskirts of town, clouds of black smoke boiled up from the highway. A fuel truck was on fire, engulfed in flames.

Another day in Baghdad. Another hit on a military convoy.

But when a photographer and I stepped out of our car to take pictures, it was clear we were stepping into another Iraq.

Insurgents flooded onto the roadway, masks over their faces, machine guns in their hands. They began to fire at approaching Humvees. The neighborhood around us scattered into a mosaic of panic. Women slammed gates behind them. Cars shot gravel from their tires as they raced away. And we were just 20 minutes outside the city center in a place that up until the last few days was as safe as any.

In Kufa, a palm-lined town on the Euphrates, bearded Shiite militiamen who swear their allegiance to a rebel cleric are driving around in police cars. American officials had just bought those police cars. American soldiers had just trained the policemen who had been riding in them.

In the Khadamiya neighborhood, one of the prettiest spots in Baghdad, men passed out grenades where just days ago children sat under umbrellas, licking ice cream. It was stunning how natural it looked, how quickly armed men seemed the norm, how nobody seemed to bat an eye, even though the heart of Baghdad now looked like the heart of Kabul.

The atmosphere in Iraq has completely changed. In just a week, a fading guerrilla war has exploded into a popular uprising. "Six months of work is completely gone,'' said a State Department official working in southern Iraq. "There is nothing to show for it.''

It was as if the clock had been set back to the early days of occupation. Again tanks are blasting apart targets in Baghdad neighborhoods. Cities like Falluja and Ramadi are under siege or, more accurately, re-siege.

But there is a difference. Back then, last April, when I was a reporter embedded with the United States Army, Iraq seemed as if it was slowly coming under control. Now, after three months on my current stint here, that nascent sense of order is collapsing into chaos.

This past week, a photographer (yes, the same one) and I headed to Ramadi, 50 miles west of Baghdad and the scene of a fierce battle that claimed the lives of 12 marines. The trip was supposed to take two hours. We had to take back roads.

The fields glowed green with rice, the palm trees swayed, and children splashed in rivers. We saw women in the doorways of mud huts squinting at us. We saw a slice of life in Iraq that was quiet and simple.

But just as I was admiring the scenery, a minivan zoomed in front of our car and blocked the road. A dozen gunmen with scarves tied over their faces jumped out. Some had heavy machine guns. Some had rocket-propelled grenades. We were surrounded. "Out! Out!" ' the men shouted. We were in a bulletproof car. Or allegedly bulletproof. Who really knew? The insurgents banged on the inch-thick glass with the tips of their Kalashnikovs. I didn't want to open my door.

But with the fatigue of one who is thoroughly defeated, I got out. I stood in the dust and watched the men level their guns at my chest. I thought about my mother. I was hoping it wouldn't hurt.

The translator and driver, usually so cool, even joking, under fire, looked terrified. One insurgent swung the safety off his gun, making a very deliberate metallic sound I hope never to hear again, and unloaded half a clip into the sky.

"Move!" he shouted.

We stepped over the hot brass bullet casings that had just been spat into the dirt and got into the minivan. We had no options. We had driven into the heart of the Sunni resistance, into a little town between Baghdad and Ramadi completely overrun by mujahedeen fighters, right now one of the most anti-American places on the planet. We later learned that we had arrived just at the time of an attack.

Our captors were not sure if we were journalists or spies. Eventually, they satisfied themselves that they could trust us. The critical moment came when a man with aviator sunglasses brought us a bowl of water.

"Drink," he said.

My mouth was so parched from fear that no sip ever tasted so wet.

"Now," he said, "you are our friends."

Later someone told me that if you are offered water - or tea, or anything in such a situation - take it. The gesture means you are a guest. And hospitality in the Arab world can spell the difference between making it out of a sticky situation or not. The man with the aviator sunglasses wasn't just giving me water. He was giving me life.

Eventually, we were allowed to drive away from the village. As we left, the insurgents launched an attack on the marines. Rockets flashed. The insurgents cheered. The last we saw of them their fists were in the air.

And I was left with the question: Why now?

Why did the Shiites, who had been patient for a year, suddenly pour into the streets to kill Americans? Why are at least some Shiite and Sunni groups, who used to be rivals, now cooperating? How did the slaughter and mutilation of four American civilians in Falluja set off a chain reaction that reverberated beyond the Sunni Triangle and jolted the entire country?

I punched out an e-mail message to Kenneth W. Stein, a Middle East historian at Emory University, who suggested in response that the killing of four American contract workers in Falluja on March 31, and the macabre celebration afterward made extreme violence possible and even invigorating.

"These examples whip up emotions, show to the public just how successful the struggle is against the foreigner, the occupier, the alien,'' Mr. Stein wrote. "Pack mentality can overcome reason and propriety.''

But before Falluja two things happened - clear in retrospect - that helped unravel what little hope was here.

The first was hundreds of miles away. On March 22, in the Gaza Strip, Israeli forces assassinated Sheik Ahmed Yassin, the leader of Hamas and a hero to Palestinians. Outraged Arabs hit the streets in Baghdad and other Middle Eastern capitals. Many Americans in Iraq braced for reprisals.

A few days after Sheik Yassin was killed, American authorities shut down the Hawza newspaper, the mouthpiece of Moktada al-Sadr, a radical Shiite cleric. The paper had been accused of printing lies. But closing it only played into Mr. Sadr's hand, fueling huge protests by his followers.

Then Falluja happened. The group that took responsibility said it was avenging Sheik Yassin.

The sheik's ghost returned to Iraq once more, on April 2, when Mr. Sadr announced that he was opening the Iraqi chapters of Hezbollah and Hamas, pro-Palestinian groups responsible for attacks on Israel.

The next day American authorities announced arrest warrants for several of Mr. Sadr's followers. His was soon to follow. Last Sunday, Iraq erupted. Mr. Sadr ordered his followers to take over government offices in Shiite areas across the country. In just days, the fighting pulled in thousands of people who weren't fighters before, and who took on a new identity. Until then, the insurgency had been a mysterious force behind a red and white checkered scarf. It had no uniform, no ideology, no face.

But Mr. Sadr provided that. Posters of him are everywhere now, even in Sunni strongholds like Falluja, something unthinkable before this crisis.

Mr. Sadr is only 31 years old. In the world of holy men, he is considered a religious lightweight. Compared with Grand Ayatollah Ali al-Sistani, the more moderate Shiite cleric whose decrees carry the force of law, Mr. Sadr's voice is just a suggestion.

But Mr. Sadr seemed to tap into a Shiite backlash percolating for some time.

Many Shiites have suffered the same humiliations as the Sunnis. They complain about soldiers bursting into their homes and harassing them at checkpoints, and all the other grievances experienced by those living under an occupation by foreigners from thousands of miles away. And as the anniversary of Baghdad's fall approached, the Shiites, who greeted American tanks with roses one year ago, had little to celebrate.

"When I wake up, I know this day is going to be a little worse than the last one,'' said Haider al-Kabi, a 29-year-old laborer from Najaf who said he was joining the resistance. "I got sick of it.''