Simple. Each island battle had been very costly in American lives.
More costly in Jap military lives, and native residents, such as Okinawa.
My Dad was healing at a Honolulu hospital, from a wound suffered landing and invading Okinawa.
He would have been among those Marines to land on Japan’s main islands, were it not for the nuclear bombs.
Estimated casualties for Americans numbered in the hundreds of thousands; perhaps topping half a million.
Without the nuclear bombs the Japs would not surrender.
The two bombs saved many human lives—Americans plus Japanese.
And those two bombs may have averted wars that could have followed.
I consider Truman’s tough decision correct, and an act of humanitarianism.