BAGHDAD -- The black-masked soldier stood at the army checkpoint examining the identification cards of each passenger, denying entry to anyone who did not live in the Sunni district of Ameriya. One resident later said entering his neighborhood now felt like crossing the border into a different country.
"This neighborhood is full of bad people," said the soldier at the checkpoint as police officers rounded up people suspected of being terrorists in Ameriya, an operation that locals said targeted them only for being Sunni.
Across the country, the sectarianism that almost tore Iraq apart after the American-led invasion in 2003 is surging back. The carnage has grown so bloody, with the highest death toll in five years, that truck drivers insist on working in pairs -- one Sunni, one Shiite -- because they fear being attacked for their sect. Iraqis are numb to the years of violence, yet always calculating the odds as they move through the routine of the day, commuting to work, shopping for food, wondering if death is around the corner.
Adel Ibrahim, a 41-year-old engineer, guessed wrong. On Aug. 6, to prepare for the evening iftar, the meal to break the day's Ramadan fast, Mr. Ibrahim went to a butcher shop in the central Karrada neighborhood to pick up meat for kebabs. Outside the shop, a Kia minivan exploded, killing Mr. Ibrahim and five others.
The next day Mr. Ibrahim's father, Saleem Ibrahim, was in tears. "They took my son and my dream away," he said.
The drastic surge in violence -- mainly car bombs planted by Al Qaeda's Iraq affiliate against the Shiite majority, and the security sweeps in majority-Sunni neighborhoods that follow -- has lent a new sense of Balkanization to this city. Security forces have increasingly restricted the movements of Iraqis in and out of Sunni areas, relying on the neighborhoods listed on residence cards as an indicator of a sect. Sunnis also fear reprisals from reconstituted Shiite militias, groups once responsible for some of the worst of the sectarian carnage that gripped Iraq just a few years ago.
Even for the hardened residents of the capital, long accustomed to the intrusion of violence into everyday life, the latest upswing in attacks has been disorienting, altering life and routines in a manner that has cast a pall of fear over this city.
The targets of the attacks are not usually government ministries or luxury hotels, places many ordinary Iraqis can safely avoid. They are the markets and cafes, mostly in Shiite areas, that dominate neighborhood routines. During morning commutes, some Iraqis are taking circuitous routes to work to avoid central streets where bombs have struck. The sight of a Kia minivan, a vehicle of choice for bombers, caught in traffic causes fear. Neighborhood soccer teams are canceling matches because those, too, have become targets.
Taxi drivers are again making decisions about where to drive based on the rising sectarian tensions that have resulted from the resurgent violence. "Last year the situation was better," said a Sunni taxi driver who gave his nickname of Abu Omar. "I wasn't afraid to go anywhere, but this year I am worried about going to Shiite neighborhoods, like Shula or Hurriya, because I keep hearing that the militias are coming back."
After Mr. Ibrahim was killed, the next wave of attacks came four days later, on Saturday evening, as Iraqis were celebrating the end-of-Ramadan festivities known as Id al-Fitr. A young bride-to-be, in her white wedding dress, sat in a hair salon when a parked car just outside blew up. The woman survived with only a small injury to her hand.
"She was so brave, she cried for a few minutes, but then decided to continue, and made it to her wedding," said Said Haneen, the owner of the salon. "That's how we Iraqis are."
Across town that evening, a cigarette vendor named Jalal Hussain was wounded in another explosion. The next morning his stall was back in business. "It's a struggle for existence," he said, as he sold a customer a pack of Marlboros. "I have to feed my family. I have to open again, as long as I am alive. I have witnessed many other explosions, but this one was the closest. We have to keep on surviving. If you are lucky, you will survive another day."
Often, the fear briefly abates after a day of bombings. Surely, the thinking goes, big attacks will not come on back-to-back days. "Customers are already calling to see if we opened or not," Mr. Haneen said on the morning after the explosion near his salon. "Today, I know there will be no explosions, as yesterday there were many. Maybe in the next two or three days we will witness another wave of bombings, but not today."
For Iraqis, the violence feels permanent, their country's perpetual decline, inevitable. The space between ordinary citizens and their political leaders, garrisoned in the increasingly fortified Green Zone, where the government has positioned new tanks and soldiers and sought to make entry even more restricted, has never felt wider.
Iraqis long ago lost confidence in the ability of their security forces, trained by the Americans at a cost of billions of dollars, to protect them.
Now they feel increasingly mocked by their leaders, whose latest pronouncements of security successes are met with revulsion.
A few hours before the attacks on Saturday evening, Prime Minister Nuri Kamal al-Maliki sent a text message to every citizen with a mobile phone, wishing all a happy Id al-Fitr and "security, stability and prosperity."
Hours after the attacks, a spokesman for the Ministry of Interior, Saad Maan, appeared on state television, praised the security forces for a job well done and said that only two people had died, including an officer trying to defuse a bomb.
But according to an Interior Ministry official and news reports, more than three dozen people were killed, and more than 100 were wounded.
This prompted mocking comparisons on Facebook between Mr. Maan and the Saddam Hussein-era information minister, Muhammad Said al-Sahhaf, who in 2003 proclaimed the Iraqi Army was valiantly pushing back the American invaders, who were in fact fast closing in on Baghdad.
This violence is real, and it appears at least partly driven by events beyond the borders of Iraq, in Syria, where a civil war is raging. The United Nations recently warned that the sectarian battlefields of Syria and Iraq are "merging," as the border between the two countries has become a revolving door for Sunni extremists.
At the same time, Shiite militiamen from Iraq, supported by Iran and the Lebanese militant group Hezbollah, head over to support the Syrian government of President Bashar al-Assad, while also reasserting themselves on the streets of Baghdad.
At the checkpoint at the entrance to Ameriya, the Sunni district, the soldier sent away a man who was trying to get to his job at a cafe.
"I've worked there for years," the man said. "You know me. Take my ID. I have to go to work."
Inside Ameriya, Othman al-Kubaisi, who owns a cosmetics store, said customers from other parts of the city had stopped coming.
"The government treats us like we have been torturing them for years, and now it's time for them to take revenge on us," he said.
Like many in this fractured city these days, Mr. Kubaisi tries to stick close to home when he can, routinely leaving only to stock up on supplies for his store.
"It's better to avoid problems and stay home," he said.
Duraid Adnan and Yasir Ghazi contributed reporting.
This article originally appeared in The New York Times.