He’s the first American I ever heard of that stood on that Japanese soil and watched the Hiroshima detonation. Bravo.
Didn’t happen - unless they put Marines on B 29s.
At least a few Americans witnessed that detonation from Hiroshima itself, although many (obviously) died in or shortly after the blast. Note: King's father would not have seen the mushroom cloud from Okinawa as some people are reading this claim, both because of the distance and because that battle ended in June 1945 and most Marines moved on to fight elsewhere. Eleven to twenty-three American POWs are reported to have been held in Hiroshima. Many died in the blast, and some may have been killed in retaliation by Japanese soldiers and civilians (eyewitness accounts are contradictory on that point). Some survived and returned home.
Among the American POWs:
Thomas C. Cartwright, pilot of B-24J "Lonesome Lady" 44-40680 shot down near Hiroshima and survived the war;
Lt. Raymond Porter, pilot SBC2 Helldiver 21079 (died);
Hugh H. Atkinson, radio B-24J "Lonesome Lady" 44-40680 (died);
John A. Long, Jr. gunner B-24J "Lonesome Lady" 44-40680 (died);
Buford J. Ellison, engineer B-24J "Lonesome Lady" 44-40680 (died);
Durden W. Looper co-pilot, B-24J "Lonesome Lady" 44-40680 (died);
Ralph J. Neal, gunner B-24J "Lonesome Lady" 44-40680 (died);
James M. Ryan, bombardier B-24J "Lonesome Lady" 44-40680 (died);
Charles O. Baumgartner, gunner B-24J "Taloa" 44-40716 (died);
Julius Molnar, gunner B-24J "Taloa"44-40716;
Ensign John J. Hantschel, 23, of Wisconsin, a fighter pilot assigned to the USS Randolph (died); and
PO3C Norman Brissette, gunner SBC2 Helldiver 21079 (died).
Other Americans reported having seen the mushroom cloud from POW facilities farther away. I was unable to confirm a United States Marine named King on that list, but it's at least possible.