|Dresden, Germany, after four Allied bombing raids, February 13-15|
According to the History.com website, the target, Dresden, was known as "the Florence of the Elbe" one the world's most beautiful cities. Less industrialized than most, it had contributed only marginally to the war effort compared to many other German cities, and since it was also less well defended, it would not have been able to put up much resistance to advancing Russian forces from the east at this stage of World War II.
Here is a section of the History.com article:
On the night of February 13, hundreds of RAF bombers descended on Dresden in two waves, dropping their lethal cargo indiscriminately over the city. The city's air defenses were so weak that only six Lancaster bombers were shot down. By the morning, some 800 British bombers had dropped 1,478 tons of high-explosive bombs and 1,182 tons of incendiaries on Dresden, creating a great firestorm that destroyed most of the city and killed numerous civilians. Later that day, as survivors made their way out of the smoldering city, over 300 U.S. bombers began bombing Dresden's railways, bridges, and transportation facilities, killing thousands more. On February 15, another 200 U.S. bombers continued their assault on the city's infrastructure. All told, the bombers of the U.S. Eighth Air Force dropped 954 tons of high-explosive bombs and 294 tons of incendiaries on Dresden. Later, the Eighth Air Force would drop 2,800 more tons of bombs on Dresden in three other attacks before the war's end.
The fires that resulted were so intense that they literally sucked the oxygen from the air, causing horrible deaths by asphyxiation and the superheated air as well as from burning men, women and children alive.
Here is a link to a graphic Youtube depiction of that terrible event, and this one to some other blogs on aerial bombings as a modern form of holocaust.