The range of the airstrikes soon expanded to include Syria, as well. Over the past year, the U.S. has run thousands of sorties in the two war-torn nations and carried out hundreds of strikes each month that the coalition's lead commander in June described as "the most precise and disciplined in the history of aerial warfare."
But according to Airwars, a London-based group of independent journalists who have been assiduously tracking the campaign, "there are clear indications" that at least 459 civilians have been killed as a result of the strikes. It pointed to 57 incidents where non-combatants were likely killed by coalition air strikes.
U.S. authorities have only made public the details of one such incident, admitting in May that a strike last November killed two children. CENTCOM is investigating at least three other reports of suspected civilian casualties, according to the Associated Press. There was no immediate White House comment on the findings.
Airwars, which describes itself as "a collaborative, not-for-profit transparency project" with no agenda other than monitoring civilian casualties, accumulated its data through a range of sources. It corroborated military information made available by the coalition governments alongside local news coverage in a number of languages, social media reports, and the work of other monitoring and rights group.
Some of the worst incidents included a recent strike on an Islamic State munitions depot in an Iraqi town: The resulting explosion may have killed as many as 70 civilians, according to local reports. Airwars spotlights a December strike on an Islamic State facility near Aleppo, Syria, where it appears "at least 58 non-combatants appear to have died when aircraft struck an Islamic State local headquarters, which was also being used as a temporary prison."
The worst casualty incidents, according to the study, are taking place in Iraq and Syria's bitterly contested major cities.
"What we are seeing in Iraq and Syria is the coalition is bombing where ISIS is, and that’s in the cities," said Chris Woods, the lead investigative journalist on the project, in an interview with the Guardian. "Unsurprisingly, that’s where we are tracking the highest number of civilian casualties."
The report, among other things, calls for improved monitoring and transparency from the coalition governments, most of which do not consistently report when and where they carry out strikes.
"You can’t have an air war of this intensity without civilians getting killed or injured, but they need to be more transparent," Woods said.