Even if the insurgents do not fight in large numbers, Marja will remain treacherous ground, littered with buried homemade explosive devices. Marine officers say it is the most heavily mined part of the country.
In the hours before the Marines landed, unmanned Predator aircraft and AH-64 Apache attack helicopters targeted men who were spotted laying roadside bombs and setting up antiaircraft guns. Eleven of them were killed in the strikes.
Civilians sought to leave the area ahead of the operation. Some made it out, in cars and on tractors piled with their belongings, but the insurgents forced others to remain in their homes, military officers said. In some cases, they said, Taliban members told residents that roads out of Marja had been mined.
About 3,500 U.S. Marines, sailors and soldiers, accompanied by about 1,500 Afghan army infantrymen, are directly involved in the mission, supported by thousands more troops at nearby bases. More than 500 paramilitary police will join the effort Sunday or Monday.