By MICHAEL S. SCHMIDT BAGHDAD - Even as the American military winds down its eight-year war in Iraq, commanders are bracing for what they fear could be the most dangerous remaining mission: getting the last troops out safely. The resurgent threat posed by militants was underscored Monday when rockets slammed into a military base in eastern Baghdad, killing six service members in the most deadly day for American forces here since 2009. In recent weeks, insurgent fighters have stepped up their efforts to kill American forces in what appears to be a strategy to press the United States to withdraw on schedule, undercut any resolve to leave troops in Iraq, and win a public relations victory at home by claiming credit for the American withdrawal. American commanders say one of the gravest threats to the 46,000 troops here is that they could become easy targets for insurgents when they begin their final withdrawal this summer and head for the border along a 160-mile stretch of road cutting through the desert into Kuwait. "Our forces were attacked today, and we were just sitting still," said Col. Douglas Crissman, who is in charge of American forces in four provinces of southern Iraq, and is overseeing highway security in them. "What is going to happen to the threat when we line up our trucks to leave and start moving out of the country?" Cash payments for tribal leaders Eight years in Iraq has taught the United States military a hard-learned lesson, that American forces cannot effectively secure large areas without the help of the local people. So commanders have fashioned an exit strategy which borrows a key element from the Awakening Movement, a successful tactical program carried out in 2006, just as the violence was peaking. The American exit strategy calls for the military to give cash payments of $10,000 a month to 10 tribal leaders. Officially, the money is paid to have Iraqis clean the crucial roadway of debris, an apparent pretense because an Iraqi-American agreement bars outright payments for security. The sheiks keep some of the cash and use the rest to hire 35 workers each who clear the road of trash. The work does make it harder for militants to hide bombs. But the military says it is aiming for more than a highway beautification project. It is hoping for local people to help police the road and the area, and to provide intelligence on militants. "I can't possibly be all places at one time," said Colonel Crissman. "There are real incentives for them to keep the highway safe. Those sheiks we have the best relationships with and have kept their highways clear and safe will be the most likely ones to get renewed for the remainder of the year." So far, the contracts have proved to be a cost-effective method for improving troop safety, even at $100,000 a month. Roadside bomb attacks on American and Iraqi soldiers stationed in the area are down, officials said, as are rocket attacks on the military base from areas controlled by the sheiks. The contracts, officials said, cost far less than nearly all the other measures the military has used in Iraq to ensure security, and sheiks provide the names of the workers so the military can conduct a security check. "The cost of a damaged MRAP that gets hit by an explosive device is $400,000, and we are not even talking about the cost of a human life," said Colonel Crissman, referring to an armored vehicle the American troops use. "Given the amount of money we have spent in this country, $100,000 to secure our highway a month is a small price to pay, especially given the importance of the highway to the withdrawal." Competing for loyalties On many days, workers can be seen raking up trash and throwing tires into pickup trucks. Several times a week, the military flies over the highway to ensure that the sections are clean. The value of the contracts - along with their limitations - is evident in roads neighboring the highway, where attacks are up. That has prompted commanders to begin to expand the program to include neighboring roads as well. And local sheiks across southern Iraq are more than eager for the cash, jockeying for a chance to collect what may the last bit of military largess. The money also helps the sheiks solidify the loyalty of their own people by giving them the power to dole out jobs. But the military says the Shiite militias are also aware of the influence cash payments can have with tribal leaders, and so they, too, try to buy allegiance, intelligence and access. "There are some sheiks who are working for the other team and are being paid well by the militants so they can operate in their land," Colonel Crissman said, referring to Shiite militants who operate in southern Iraq. Shiite militias and followers of the anti-American Shiite cleric Moktada al-Sadr have been some of the United States' fiercest enemies in Iraq. The groups, which have close ties to Iran, have stepped up their anti-American activities recently as Iraqi lawmakers in Baghdad have debated whether to ask the Americans to stay past their scheduled departure date. Last week, followers of Mr. Sadr, whose Shiite militia, the Mahdi Army, was largely defeated three years ago, held a mass demonstration in Baghdad in which they marched unarmed in formations, trampling over American flags and calling for the Americans to withdraw. The potential value of the highway cleaning contracts was illustrated last month when a reporter for The New York Times accompanied Lt. Col. Robert Wright to a lunch with tribal leaders. The meeting, which took place in a tent in the middle of a barren stretch of dessert, lasted for three hours, as the tribe's leaders and Americans ate from large platters of rice and lamb and talked about their families and Iraqi politics. Then on the ride back toward the American base, one of the tribal leaders offered a bit of intelligence regarding Shiite militants who he said met regularly in an open field. The colonel said he was interested - and then the local leader raised the topic of a contract, to clean the highway. Video: 5 US soldiers killed in Iraq rocket attack Open in new window Closed captioning of: 5 US soldiers killed in Iraq rocket attack >>>we turn to overseas in iraq today. we haven't had news like this in a while. five americans were killed in a rocket attack in baghdad. the deadliest single day for the u.s. there since '09, and today, of course, five american families got the worst possible news.