Reporting from Washington — Efforts to reduce civilian casualties by restricting U.S. airstrikes and other uses of force in Afghanistan are also sparing American troops from attack, according to a study to be unveiled Tuesday.
The study by the National Bureau of Economic Research, being released at the nonpartisan New America Foundation in Washington, undercuts the notion that the military faces a zero-sum choice between protecting its troops and protecting civilians, said one of the authors, Jacob Shapiro of Princeton University.
"Doing a little bit more to protect civilians looks like it reduces the rate of attacks" on troops, he said.
Tighter rules of engagement put in place last summer by Army Gen. Stanley A. McChrystal have provoked complaints among U.S. troops that their lives have been put at risk.
Under those procedures, commanders could not fire on buildings or other sites where they had reason to think civilians might be present unless their own forces were in imminent danger of being overrun. They also were told to break off engagements and withdraw rather than risk harming noncombatants.
McChrystal's replacement, Army Gen. David H. Petraeus, promised lawmakers last month that he would reexamine how the rules had been implemented, while expressing overall support for them.
The study, funded by the Air Force and Stanford University, analyzed 4,000 civilian casualties and 25,000 fights between U.S.-led forces and insurgents over 15 months ending April 1. A typical incident that caused two Afghan civilian deaths provoked six revenge attacks in the district by the Taliban and other militants, the study found.
"The data are consistent with the claim that civilian casualties are affecting future violence through increased recruitment into insurgent groups after a civilian-casualty incident," the study says.
Pentagon officials, including Defense Secretary Robert M. Gates, have long acknowledged that civilian casualties were fueling the insurgency in Afghanistan, which is why McChrystal pushed hard to reduce them. Officials have noted that the Pashtun ethnic group, which dominates the Afghan insurgency, lives by a code of honor requiring men to avenge the deaths of relatives.
The study also examined Iraq, finding that civilian casualties in a particular district did not result in a similar long-term increase in insurgent violence in that district. The finding is consistent with what U.S. military officials have observed. In Iraq, the U.S. military has tamped down anger over civilian casualties by making payments to families. That approach has been greeted with affront in Afghanistan.
McChrystal's restrictions on U.S. airstrikes and mortar attacks have resulted in fewer civilian deaths attributed to American forces this year, according to a July report by the Afghanistan Rights Monitor, a watchdog group often critical of U.S. policy.