During WWII the air forces of the Allies set waves of bombers to attack the city of Dresden in Germany. As a result of the bombing, a huge fire storm erupted, and consumed eleven square miles of the center of the city.
Dresden had no military targets to speak of, and was overflowing with refugees (this was February of 1945, and the war was going badly for the Nazis). Estimates of the civilian death toll range from 70,000 to 135,000 or more.
Kurt Vonnegut, Jr. was in the city as a POW at the time, and witnessed the carnage firsthand. He later
wrote about it in the novel Slaughterhouse Five.