“The Invasion of Okinawa is what made the atomic bombing of Japan inevitable.”
Yes, that’s the argument I’m familiar with the longest, that it in reality saved many more lives than if an invasion of the main islands of Japan had to be made.
Also, Okinawa provided some documentation of defense plans for the home islands, to include use of ‘dirty bombs’ on the landing areas, coupled with use of poison gas. Japan planed to accept 30 million casualties to force a million US deaths.
The US still issues purple heart medals minted in preparation for the invasion of Japan. Here is an irony: The dropping of the Nagasaki bomb was probably the single most humanitarian action in the history of the world.