On August 6, 1945, the atomic bomb Little Boy was dropped on Hiroshima, Japan, leading to the deaths of up to 166,000 people. A second nuke, called Fat Man, was dropped on Nagasaki the following day, killing even more citizens and forcing the Japanese government to end the war due to fears of further attacks.
In the Kaiju Multiverse
Ishiro Serizawa and his father survive the atomic bombing of Hiroshima, encountering a newly-awoken Shinomura that flies away. Godzilla lurked in the waters just outside. Ishiro's father leaves him with his grandparents in Kyoto and goes with the Japanese Navy. (Godzilla: Awakening)