Inside the Surge.(Ghazaliya)

Joint Security Station Thrasher, in the western Baghdad suburb of Ghazaliya, is housed in a Saddam-era mansion with twenty-foot columns and a fountain, now dry, that looks like a layer cake of concrete and limestone. The mansion and two adjacent houses have been surrounded by blast walls. J.S.S. Thrasher was set up last March, and is part of the surge in troops engineered by General David Petraeus, the American commander in Iraq. Moving units out of large bases and into Joint Security Stations--small outposts in Baghdad's most dangerous districts--has been crucial to Petraeus's counterinsurgency strategy, and Thrasher is now home to a hundred American soldiers and a few hundred Iraqis. This fall, on the roof of the mansion, amid sandbags, communications gear, and exercise equipment protected by a sniper awning, Captain Jon Brooks, Thrasher's commander, pointed out some of the local landmarks. "This site was selected because it was the main body drop in Ghazaliya," he said, indicating a grassy area nearby. "There were up to eleven bodies a week. Most were brutally mutilated."

The Mother of All Battles Mosque, with its unmistakable phalanx of minarets shaped like Scud missiles, is nearby. Saddam Hussein hid in Ghazaliya during the American bombing in the first Gulf War, and built the mosque to show his gratitude to the neighborhood. ("Ghazaliya used to have--still does--a lot of retired Saddam military people," Brooks said.) In April, 2004, wounded gunmen taking part in the battle for Falluja took refuge in the mosque. Ghazaliya borders the eastern edge of Anbar province, the center of the Sunni insurgency, and it became a strategic gateway to Baghdad for insurgents and foreign jihadis. On a previous visit to Ghazaliya, in December, 2003, I had met insurgents at a safe house in the neighborhood. They told me that they were intent on killing Americans. Since those days, with few exceptions, Ghazaliya had been a no-go area for Westerners, including journalists, who ran the risk of being kidnapped and killed. American patrols in Ghazaliya were regularly ambushed.

Captain Brooks is twenty-eight, of medium height and a stocky build, with close-cropped brown hair. From the roof, he pointed to where Sergeant Robert Thrasher, for whom the J.S.S. was named, had been killed by a sniper, last February. At the time, the company was working out of Camp Victory, the American base encompassing a large swath of Baghdad, including the airport. Thrasher was twenty-three; he had joined the Army out of high school.

Despite the insurgency's influence, Ghazaliya remained, at first, what it had been for decades--a middle-class Baghdad neighborhood in which sectarian tensions were more or less held in check. The vast majority of the estimated hundred thousand residents were Sunni, but, Brooks said, "there were a lot of professionals, college-educated Sunnis, and Shias, too, and mosques for both." The neighborhood changed after February, 2006, when Sunni militants bombed the ninth-century Askariya shrine, in Samarra, one of the Shiites' holiest sites, and sectarian violence flared up across Iraq. Shiite militias, foremost among them the Mahdi Army, pushed deeper into Ghazaliya from Shulla, a poor, sprawling Shiite neighborhood just to the north. The Sunnis responded by turning to hard-line insurgents and to the foreign jihadis of Al Qaeda in Mesopotamia, whom the U.S. Army called Al Qaeda in Iraq.

"You had Sunni extremists in the area before Samarra. After Samarra, though, Al Qaeda in Iraq came on strong," Captain Brooks said. "They had death squads. They systematically selected people because of the locations of their houses, or their relationships. They brutally tortured them, killed them, and dumped their bodies." Shia families, and many Sunnis--those who had the financial means--fled the neighborhood. By the beginning of this year, southern Ghazaliya was under the de-facto control of Al Qaeda in Mesopotamia, while the northern part of the neighborhood was besieged by Shiite militiamen. "Twenty dollars and a phone card could get you an I.E.D. placed," Captain Brooks said, referring to the improvised explosive devices that have caused the majority of American military deaths in Iraq. "The people realized they had let something in that they couldn't control."

President Bush, after securing Secretary of Defense Donald Rumsfeld's resignation, in November, gave his new war team--Secretary of Defense Robert Gates and General Petraeus--an opportunity to change the strategy in Iraq, and in February the surge began. The plan called for thirty thousand extra troops; estimates of the actual number run as high as fifty thousand. Thirty-four Joint Security Stations were opened in Baghdad, three of them in Ghazaliya: the first, J.S.S. Casino, in northern Ghazaliya; next, in the southwest, J.S.S. Thrasher; and, last May, J.S.S. Maverick, in the southeast.

Brooks pointed to a large house with broken windows across from the base. His men called it the Cannister-Round House, because when they were first moving in snipers had fired on them from inside, and they responded by lobbing tank shells into the house. "We don't get shot at anymore," he said. Brooks's men began the manpower-intensive work of conducting systematic patrols by day and aggressive raids at night; William Bushnell, a sergeant in Brooks's company, was killed on one of those patrols in April. Previously, Brooks's men had headed back to the heavily fortified Camp Victory after roving through Ghazaliya. With the surge, the Americans became a permanent presence in the neighborhood. After they moved in, the U.S. Army erected twenty miles of concrete walls in Ghazaliya, both to separate Shiite and Sunni residents from each other and to establish secure perimeters. Brooks said that his unit's success had been made possible by his colleagues at J.S.S. Casino, who kept Shiite militiamen from Shulla out of the neighborhood.