Is this largest single civilian mass killing by an army with single strike since WW2 or there are something in between? Many evacuation ships were attacked by

Is this largest single civilian mass killing by an army with single strike since WW2 or there are something in between? Many evacuation ships were attacked by Russians during WW2 that killed large number of civilians in one incident. Terrorist strikes have been with large amount of victims, especially in Iraq but the biggest was of course 9/11, but I could not recall anything like this by an army.