WASHINGTON – A U.S. airstrike in March killed over 100 civilians when the bomb set off a secondary explosion rigged by ISIS in the targeted building, according to a report released by the U.S. military Thursday.
The U.S. strike on March 17 triggered explosives that had been strategically rigged by ISIS militants, causing a much larger explosion than expected, taking down the reinforced concrete structure and crushing those inside.
The two-month long Pentagon investigation found that 105 civilians had been killed in the strike — 101 inside the targeted two-story building that had a partial basement, and four in an adjacent structure. Thirty-six civilians believed to have been inside the building have not been found.
The death toll is likely the highest civilian death count from a single incident since the U.S.-led air campaign against ISIS began in 2014.
The strike prompted rights groups to accuse the U.S. of not taking enough precautions to protect civilians. The Pentagon report, however, places the blame for the civilian causalities largely on ISIS.
“Our condolences go out to all those that were affected,” Maj. Gen. Joe Martin, commanding general of the ground force fighting ISIS, said in a statement. “The Coalition takes every feasible measure to protect civilians from harm. The best way to protect civilians is to defeat ISIS.”
The investigation found that two ISIS snipers had positioned themselves on the building and fired on Iraqi forces, who then called in a U.S. airstrike. The U.S responded by dropping a GBU-38 munition, which holds 192 pounds of explosives. That bomb, according to the Pentagon, should have resulted in damage to the structure localized to the front of the second floor where the bomb detonated, but should not have taken down the reinforced concrete building.
Investigators conducted a post-blast analysis and found residue from the scene inconsistent with the GBU-38. That residue, they found, had signatures of explosives used by ISIS and showed signs that they had been rigged to explode more easily. The report noted that investigators found a second blast crater at the rear of the structure that was not caused by the GBU-38.
The investigation found that neither U.S. or Iraqi forces were aware that civilians were in the building. It also found that U.S. and Iraqi forces were unaware that ISIS had rigged the building with additional explosives.
Lead investigator Air Force Brig. Gen. Matthew Isler told reporters via teleconference at the Pentagon Thursday that it appeared that ISIS had deliberately created a situation to draw U.S. airpower, knowing that the airstrike would trigger a secondary explosion.
“The secondary explosion caused a rapid failure of the structure,” Isler said.
The Iraqi Counter Terror Services troops had been watching the building for two days prior to the strike and saw no sign of civilians inside, Isler said. The weather prohibited coalition reconnaissance aircraft from monitoring the scene in the two days prior, according to Isler. He said prior to that, reconnaissance aircraft had not seen any indication that civilians were inside.
Isler said that civilians killed in the building may have gone there voluntarily because it was one of the best constructed in the area, and potentially went to the basement to escape the fighting raging around them. He said it’s unclear if they were held against their will, but that people in a neighboring building were threatened by ISIS the night before the U.S. airstrike to not leave.
U.S. investigators traveled to the scene of the incident on two separate occasions to evaluate the structure and collect samples for analysis, Isler said. Investigators also worked with regional and western news outlets and non-government organizations active in the area, he said.
Isler said the U.S. military will make condolence payment, or “solatia,” if the claims from next of kin can be substantiated. The claims have rarely been substantiated during the conflicts in Iraq and Syria.
The U.S.-led coalition has adjusted its tactics, techniques and procedures to prevent another incident like the March 17 attack, Isler said. He would not speak to how protocols have changed, however, citing the need to keep ISIS unaware of the particulars.
The latest publicly released tally of civilian deaths caused by the U.S.-led coalition, ahead of the Thursday report, put the toll at 352 individuals. This number is far fewer than that of independent investigators.