My uncle, lieutenant Wallace W Furman, was a fighter/bomber pilot in WW11. He island hopped in the Pacific theater until finally in position to fly daily strafing/bombing runs on mainland Japan. One morning briefing, before their daily mission, he and the other pilots that day were ordered to be off the mainland and returning to base at a certain time... No excuses.
As he left the mainland to return he felt this enormous shock wave, he turned in his seat and saw the mushroom cloud rising above Hiroshima. Of course he had no idea what it was. Upon his return to base he was told he witnessed history and hopefully an end to the war.