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.