A lot of men were killed in that war, thousands per day. Who knows your father could have been one if they had not done it when they did. 3 members of my family were killed just days before. The war needed to end.
Big difference between that and Ukraine. Japan stated the war with the US. Russia started the war with Ukraine.
As I said, that was solely to hurry the war to a faster and less bloody (for the US) end. If the Japanese had been close to ending America, I’d expect FDR/Truman to pull out all the stops before letting that happen.
That’s just how it works, you do whatever it takes to stop the enemy.
And that’s even setting aside the possibility of itchy trigger fingers all on edge setting something off by accident or mistake.
https://www.atomicheritage.org/history/nuclear-close-calls-cuban-missile-crisis