Hiroshima On Aug, 6, 1945, this Japanese city and military base were the targets of the first atomic bomb dropped as a weapon. The explosion had the forse of 20,000 tons (20 kilotons) of TNT. It destroyed more than four square miles and killed or injured 140,000 people, according to an official count taken between August and December 1945. Hiroshima city officials say the toll may be 220,000 if including those who died after December 1945 of non-acute injuries or radiation.