Although the ethical and legal issues surrounding civilian casualties committed by combatants during war have been widely debated, the consequences for military operations in harming civilians, even when inadvertent, are much less well understood. As the United States considers deploying more troops to Afghanistan and continues to use drones against suspected militants in countries such as Pakistan, this issue is all the more pertinent. 

In a forthcoming study of the Iraq war in the Journal of Conflict Resolution, we sought to inform the discussion on this topic by focusing specifically on the operational consequences of harming civilians. We examined how locals reacted to accidental civilian deaths caused by both multinational forces and Iraqi insurgents and found that both parties suffered very real consequences when they harmed civilians. We used newly declassified U.S. Defense Department data on the weekly number of tips that Iraqis supplied to British, Iraqi, and U.S. government forces between June 1, 2007, through June 27, 2008, one of the most intense periods of the war. Tips provided throughout the war covered a variety of sensitive war-related matters, including the locations of terrorists and the whereabouts of weapons caches. Combining this data with U.S. military and civilian casualties during combat from the British nongovernmental organization Iraq Body Count, we found that when insurgents killed civilians, locals shared information with U.S. allied forces more often. When multinational forces were responsible, civilians shared less.

Although both sides of the conflict paid a price for harming civilians, the cost to U.S. forces and their allies was greater. Specifically, we estimate that for every two civilian deaths caused by multinational forces, Iraqis provided roughly two fewer tips the following week. When insurgents were responsible for the same number of deaths, civilians supplied approximately one additional tip over the same period of time. Our results suggest that there are very real consequences for the success of counterinsurgency efforts, since changes in information flow affect the ability of government forces and their allies to target insurgents. Past analysis of the conflict in Iraq is consistent with this theory: increases in civilian casualties caused by U.S. coalition forces were followed by increases in insurgent attacks against them, while increases in insurgent harm to civilians were followed by fewer incidents against U.S. forces.

Similar dynamics likely exist in other asymmetric conflicts that require crucial intelligence to defeat an insurgent force, including Afghanistan, where the Taliban, equipped with little more than small arms and improvised explosive devices, has survived roughly 15 years of counterinsurgency efforts led by the world’s most powerful military.

Counterinsurgency theorists and practitioners have long held that information is critical to the outcome of counterinsurgency campaigns. As our colleague David Ensign and one of us have previously written:

…while state forces tend to be stronger than the insurgents who challenge them, they lack information about the insurgency—the identities of its members, the locations of its weapons caches, and so forth... In other words, although a power asymmetry typically benefits counterinsurgents, an information asymmetry benefits the insurgents, more or less offsetting the difference in power. Local informers, therefore, threaten to upset this balance by tipping the information advantage away from the insurgents.

A group of scholars has likewise noted in the Journal of Politics that information about insurgent activities is “a central resource in civil wars,” so much so that “counterinsurgents seek it, insurgents safeguard it, and civilians often trade it.” In the case of Iraq, tips supplied by locals were associated with a variety of battlefield successes, such as major discoveries of weapons caches, including over 450 mines capable of destroying armored tanks in the Iraqi city of Sadr, a stronghold for the insurgent militia of Muqtada al-Sadr, a radical Shiite cleric. Local informers also enabled the U.S. forces to find several bomb-making facilities in Iraq, which led to the arrests of hundreds of key former Baathist and al Qaeda members. Tips also helped the United States find and kill Abu Musab al-Zarqawi, the leader of al Qaeda in Iraq, the group that eventually became the Islamic State (or ISIS). 

Of course, tactical significance varies depending on the quality of the tip. In some cases, tips produced meaningful but relatively small counterinsurgency successes. For example, as one U.S. Defense Department press release notes, “[a]n early morning tip from local residents led members of the 101st Airborne Division’s 1st Brigade Combat Team to an area near Kirkuk, where they found two IEDs.” In other cases, however, tips led to more significant successes. For instance, another Defense Department report notes that a single tip led coalition forces to a bomb-making facility in western Iraq, complete with an array of hazardous substances, “including canisters of chlorine, several 55-gallon barrels of nitric acid, and several bags of fertilizer.”

Given the many tens of thousands of Iraqi civilians who were injured or killed during the war, we suspect that civilian casualties played a major role in shaping information dynamics throughout the conflict. Perhaps most importantly, our findings provide the first empirical confirmation that civilians are not mere bystanders during conflict—their responses are strategically significant. In addition to the legal, ethical, and political imperatives for minimizing harm to civilians during conflict, there is also now good evidence that doing so makes good strategic sense as well. 

For this reason, reports indicating that the United States’ has relaxed rules in minimizing civilian casualties in Somalia and Yemen while easing standards relating to the oversight and investigation of such deaths deserve particular scrutiny. An intensification of efforts to target militant groups, such as ISIS, that fails to maintain high standards for reducing harm to civilians could well complicate long-term stability even if it offers short-term military success. As these insurgents are weakened and driven underground, eradicating them will require a steady stream of intelligence from locals. And that will be easier to obtain if the United States and its allies show great care for locals’ lives in the near term.

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  • ANDREW SHAVER is a Doctoral Candidate at Princeton University’s Woodrow Wilson School of Public and International Affairs and a research fellow at Harvard University’s John F. Kennedy School of Government.
  • JACOB N. SHAPIRO is Professor of Public and International Affairs at Princeton University and Co-Director of the Empirical Studies of Conflict Project. 
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