A single top secret American strike cell launched tens of thousands of bombs and missiles against the Islamic State in Syria, but in the process of hammering a vicious enemy, the shadowy force sidestepped safeguards and repeatedly killed civilians, according to multiple current and former military and intelligence officials.

The unit was called Talon Anvil, and it worked in three shifts around the clock between 2014 and 2019, pinpointing targets for the United States’ formidable air power to hit: convoys, car bombs, command centers and squads of enemy fighters.

But people who worked with the strike cell say in the rush to destroy enemies, it circumvented rules imposed to protect noncombatants, and alarmed its partners in the military and the C.I.A. by killing people who had no role in the conflict: farmers trying to harvest, children in the street, families fleeing fighting, and villagers sheltering in buildings.