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In 2017, Mara Revkin was doing doctoral research just outside the Iraqi city of Mosul while the battle to defeat the Islamic State (IS) militant group was underway. Midway through the nine-month battle, after East Mosul was liberated, the conflict shifted to West Mosul, across the Tigris River. 

Revkin, now a professor of law and political science at Duke Law School, noticed that the number and frequency of airstrikes seemed to have increased sharply in this new phase of fighting, causing immense civilian death and property damage.

This was a notable departure from the focus on ground warfare during the first phase, in which Iraq’s Counter-Terrorism Service (CTS, also known as the Golden Division) fought house-by-house and neighborhood-by-neighborhood to clear the city of IS fighters. What, she wondered, were the reasons behind this shift, and how would it affect the city’s civilian population of more than 1 million?

Revkin, fellow Duke Law professor Jonathan Petkun, and Benjamin Krick, a Duke doctoral student in political science, explore this question in “Civilian Harm and Military Legitimacy: Evidence from the Battle of Mosul,” published in International Organization.

The differences between the two phases of warfare in East and West Mosul gave rise to naturally occurring variation that approaches the necessary conditions for a natural experiment, making it possible to study how civilians perceive the legitimacy of counterinsurgent forces operating in their midst through a mixed-methods approach that combines quantitative and qualitative analysis of a survey of 1,458 residents in East and West Mosul, satellite data that recorded damage to the city, and interviews conducted with residents of Mosul in 2017, 2018, and 2023. 

Armies in conflict zones are always thinking about how to protect their own forces while minimizing civilian harm, for reasons that include perceptions of their own legitimacy. “There are some inherent and difficult tradeoffs that we were always thinking about,” said Petkun, who served in Iraq as a U.S. Marine Corps logistics officer and foreign military advisor. “What kinds of weapon systems you use, what types of vehicles you use in various operations — there are tradeoffs between what is most protective of US military forces, and what is potentially most protective and respectful of civilians.”

But the calculus around those tradeoffs has shifted. “There has been a move towards minimal troops on the ground, and more reliance on high-tech weapons that can be called in from elsewhere,” such as drones or airstrikes, explained Petkun. “And so we are implicitly making some of these tradeoffs about force protection of U.S. troops versus civilian harm reduction without necessarily having discussed, ‘Is this appropriate? Does it accomplish the mission, and is it protective of civilian lives?'”

Too often, Petkun and Revkin said, questions of military legitimacy are discussed as a narrow matter of military strategy, without input from the local population, even as conflicts around the world take an increasing toll on civilian lives.

The qualitative nature of their work, which captured Moslawis’ observations and sentiments, shows that “high levels of civilian harm resulting from indiscriminate bombing and less restrained methods of fighting war can have really negative effects not only on the wellbeing of civilians but also on their attitudes toward militaries,” said Revkin. “That seems particularly worth saying right now.” 

A change in strategy and fighting forces brings change in perceptions

The battle’s move from East to West Mosul illustrated this trend, as a strategy of urban warfare in East Mosul was replaced by heavier reliance on airstrikes and artillery in West Mosul.

The authors say it was marked by several other changes as well: shifting from a strategic objective of “attrition” to one of outright “annihilation,” and from the more professional Golden Division corps to the less professional Federal Police forces. The personnel change was due to the heavy casualties suffered by the Golden Division, which lost 75 percent of its members in East Mosul.

The authors hypothesized that West Moslawis would perceive the counterinsurgent forces as less legitimate compared with East Moslawis, given that West Mosul was far more heavily bombed, more civilians were killed, and the Federal Police were more likely to loot and exhibit other unprofessional conduct.

Their second hypothesis was less intuitive – they thought that respondents in West Mosul would still feel this way, even when controlling for how much they were personally exposed to harm from the conflict.

“A person who's had the same exposure to having a member of their household killed or had their property destroyed still has a different attitude towards the military and its legitimacy in East versus West Mosul,” said Revkin. “Why is that?”

The answer lies in their theory of military legitimacy. Civilian perceptions of legitimacy are shaped by their observations of two inputs, both borrowed from international law and theory: just cause and just conduct. Their assessment will depend “not only on what civilians experience at the hands of armed actors, but also how they experience it — whether or not combatants’ conduct is just — and why they experience it — whether or not they approve of the cause for which combatants are fighting,” the authors write.

Their statistical analysis found that their second hypothesis held up — that West Moslawis viewed the Iraqi forces as less legitimate even after controlling for personal exposure to harm and neighborhood-level exposure to harm. Just as compelling was evidence from the qualitative interviews they conducted. One respondent described how a Golden Division fighter saw her father, who has Parkinson’s disease, fall while they were fleeing and drove them in his own car to the hospital.

“It definitely put that soldier himself at increased risk because he put down his weapon in order to do this,” noted Revkin. “And that really brought home the importance of the visible sacrifices that combatants can and do make when they put themselves at risk in order to protect civilians.”

West Moslawis were also cognizant that the airstrikes they were experiencing were an explicit choice made by the counterinsurgent forces, and that there were alternative, and perhaps more just, ways of conducting the counterinsurgency.

Multiple interviewees pointed out that IS fighters could have been pushed out of Mosul to the surrounding desert and killed by airstrike once they were away from the densely populated city. With the growing reliance on fighting from the air instead of on the ground among local populations, Revkin and Petkun fear that troops in the future will have fewer opportunities to demonstrate compassion toward civilians, leading to a decline in perceptions of military legitimacy.

“Even if the pilot is following rules of engagement and all of the correct steps are being taken in terms of verifying intelligence, none of that process is visible to civilians on the ground,” said Revkin. “Whereas they can see the soldier who stops what he's doing and puts down his weapon.”