American military archives reveal that if the Japanese had not surrendered on August 15, 1945, they would have been hit by a third and potentially more powerful atomic bomb just a few days later and then, eventually, an additional barrage of up to 12 further nuclear attacks.

Documents highlighted during commemorations to mark the 70th anniversary of the bombings of Hiroshima on August 6, and Nagasaki on August 9, which forced the end of World War II, show the determination of the United States to make Japan surrender unconditionally.