WASHINGTON — The Pentagon on Tuesday blamed “unintentional” human mistakes for the American-led airstrikes in September that killed dozens of Syrian government troops. The attacks were conducted under the “good-faith belief” that the targets were Islamic State militants, according to the official inquiry.
The investigation, led by an Air Force general, concluded that the strikes did not violate the law of armed conflict or the rules for the American military. Danish, British and Australian forces also participated in the strikes.
“In my opinion, these were a number of people all doing their best to do a good job,” said Brig. Gen. Richard A. Coe, the officer who led the investigation.
At the time, the Russians, who have been working closely with the forces of President Bashar al-Assad of Syria to fight the Islamic State and other rebels, said the attack had killed 62 Syrian troops and wounded more than 100.
Russia said the strikes had enabled the Islamic State to capture more territory. The Syrian government said they were “a very serious and flagrant aggression” and accused the United States of supporting the Islamic State in its efforts to overthrow Mr. Assad.
The strikes occurred as a deal to ease hostilities in Syria, brokered by the United States and Russia, was unraveling. They undercut American efforts to reduce violence and further exposed the challenges faced by the Obama administration in Syria.
According to a redacted copy of a report that summarized the investigation, a drone examined an area near an airfield in Deir al-Zour Province in eastern Syria on Sept. 16, identifying a tunnel entrance, two tents and 10 men. The forces were not wearing recognizable military uniforms or identification flags, and there were no other signs of their ties to the government, the inquiry found.
“In many ways, these forces looked and acted like the Daesh forces the coalition has been targeting for the last two years,” General Coe said, using the Arabic acronym for the Islamic State.
“Human factors like ‘confirmation bias,’ ‘improper labeling’ and ‘invalid assumptions’ resulted in labeling of individuals as Islamic State of Iraq and Levant forces early in the process, which colored later analysis and resulted in continuing misidentification of the forces on the ground,” the United States Central Command, which oversees American military operations in the Middle East, said in a statement.
The next day, drones and jets were deployed to attack the airfield. They began hitting tanks and armored vehicles. In all, 34 precision guided missiles were dropped on the Syrian forces.
An hour after the strikes began, the Russians informed the United States that the coalition was attacking Syrian forces. Four minutes later, the strikes were halted.
The investigation laid out a series of changes to the targeting process that the military has already made, including more information-sharing among analysts. The Air Force is also reviewing its process for identifying targets.
“In this instance, we did not rise to the high standard we hold ourselves to, and we must do better than this each and every time,” said Lt. Gen. Jeffrey L. Harrigian, the commander of the Air Forces within the Central Command.