Khalid Moustafa's family has no idea who killed him, or why. Moustafa, a Kurd, was a yogurt seller and taxi driver, the husband of an Arab woman and the father of five children, with a sixth on the way. He was found in pieces, his head near his home, his body left by a highway. "Mosul is a butchery," says the victim's father, asking that his name be withheld to protect the rest of his family.Moustafa's murder is part of a recent wave of killings that threatens to turn this multiethnic, Arab-dominated northern gateway city into the next Fallujah, as areas of the city are slipping out of the control of U.S. forces and the Iraqi government.Life still appears normal in many parts of Mosul, especially in the Kurdish neighborhoods on the eastern side of the Tigris River. Stores are open, traffic is thick and the Iraqi National Guard patrols the streets. But much of Mosul has become an incubator for regional terrorist groups like Ansar al-Islam, the Kurdish fundamentalists, and for foreign fighters crossing the still unsecured border from Syria, according to U.S. and Iraqi security officials. "Many kinds of criminals and terrorists come into Mosul from Syria. It's like the Super Bowl for them," says Salim Kako, a top official of the Assyrian Democratic Movement, which represents many Christians in Mosul. The outsiders have mixed with Mosul's homegrown fundamentalist Islamic opposition and a potent Baathist resistance fueled by the city's large number of unemployed soldiers. This stew of local and outside insurgents is stepping up attacks on American and Iraqi security forces — and anyone suspected of collaborating with them. Week after week, car bombings, improvised explosives and shootings take a steady toll of Iraqi National Guard and U.S. personnelThe insurgents hope to pull Mosul apart by targeting those people best-placed to help unify it. Threats and assassinations often target the city's professional classes, workers in its economically vital oil industry and known political moderates. "Anyone who advocates freedom and democracy is considered to be publicly for America and a target," says Rooa al-Zrary, a Mosul journalist whose father, the editor of a moderate newspaper, was murdered last year. Doctors are fleeing, finding work in Erbil. "The situation is bad and getting worse," says a surgeon at Salaam Hospital, the city's largest. Adds a colleague: "We feel like there are eyes watching everyone, and that the resistance is growing stronger every day." At Mosul University, teaching is now a dangerous occupation. The dean of the college of law was found dead outside her home, along with her husband. And three professors have been murdered, including the head of the political science and the translation departments.Mosul's cosmopolitan character is also under attack. "The mosaic of Mosul is a miniature Iraq: Arabs, Kurds, Turkomans, Assyrian Christians, Nestorian Christians, Muslim Sunnis, Muslim Shi?ites, Yezidis and Armenians," says Sadi Ahmed Pire, the Mosul chief of the Patriotic Union of Kurdistan, one of Kurdish Iraq's two governing parties. By attacking this mosaic, he says, "the Syrians and the resistance are trying to create anarchy." Minority groups viewed as sympathetic to the Americans are particularly vulnerable. A Christian church was bombed in early August, and Christians have been among those murdered. Pire says he has survived several assassination attempts.Tal Afar, a city 30 miles west of Mosul populated almost entirely by Iraqi Turkoman, was overrun by terrorist groups this summer. In early September, the U.S. Army laid siege to the town and the ensuing two-week battle was so fierce that the Turkish government complained that Americans were killing innocent Turkoman civilians. Many Mosul residents worry that Tal Afar was a dry run for their city.The sad irony is that Mosul had once been a postwar model for U.S. involvement in Iraq. From April 2003 until last February, the city was under the command of the 101st Airborne Division, led by Lieut. General David Petraeus, who tried to be sensitive to local concerns. Several residents fondly recall particular soldiers by name. "Tell Mr. Anderson of the 101st Airborne that a Moslawi girl salutes him," says a schoolteacher. The 101st devoted itself to economic-development projects, including restarting a cement factory that had been one of the city's biggest employers. These days the local economy has stalled as foreign companies have fled. According to Pire, about 600,000 breadwinners are unemployed in a city of somewhere between 2.6 million and 3 million people.The 20,000-strong 101st is gone, replaced last February by the 8,700 soldiers of Task Force Olympia, a multinational brigade of coalition troops. Although they include a large number of U.S. National Guard reservists, American soldiers have largely taken a backseat to the Iraqi National Guard. So far, as in the rest of Iraq, the performance of these new units has been mixed. "The current invisibility of American soldiers has made people happier. People feel more comfortable with Iraqi soldiers," says Dindar Doskar, head of the Mosul office of the Kurdish Islamic Union (KIU). "But there are not enough Iraqi soldiers and police, and the terrorists have better weapons." Because of that threat, politicians in Mosul say the nationwide elections scheduled for January are likely to be turbulent there. "Who is going to vote under these conditions?" asks the KIU's Doskar. The offices of the major political parties have already been attacked. Predicts Doskar: "There will be car bombs at voting stations just like there are car bombs at police-recruiting stations." And perhaps heads left on the sidewalks to give awful testimony to Mosul's deepening crisis.