"In the following waves [after the initial blast] people's bodies were terribly squeezed, then their internal organs ruptured. Then the blast blew the broken bodies at 500 to 1,000 miles per hour through the flaming, rubble-filled air. Practically everybody within a radius of 6,500 feet was killed or seriously injured and all buildings crushed or disemboweled." -- From the article "Atom Bomb Effects," LIFE, 3/11/1946. Above: Hiroshima, 1945, by Bernard Hoffman. To this day, of course, historians, politicians, and military men and women the world over argue whether the American use of atomic weapons in WWII was, in fact, justified. That the bombs hastened the end of the war is, on the other hand, something that even the United States' fiercest critics generally concede. One week after the obliteration of Nagasaki, Japan surrendered.
From LIFE.com's never before published pictures of the aftermaths of Hiroshima and Nagasaki.