In spring and summer 1945, American politicians, generals and scientists pondered how to best use the terrible power of the atomic bomb created by the Manhattan Project in New Mexico.

They deliberated killing tens of thousands of civilians to end the war with Japan, attacks finally carried out on the president’s authority.

It’s been 75 years since the U.S. Army Air Force dropped atomic bombs on Hiroshima and Nagasaki on Aug. 6 and 9, 1945, respectively. Both cities were basically leveled, and hundreds of thousands of people were killed or injured.

After Nagasaki, the Japanese realized further resistance was futile. They surrendered, but only on the condition that the emperor retain his throne.

The battleship USS Missouri steamed into Tokyo Harbor, the surrender documents were signed, Gen. Douglas MacArthur called it good and the rest is history.

Not so fast.

Alex Wellerstein, a historian of science at the Stevens Institute of Technology in Hoboken, N.J., author and blogger on atomic bomb history, said time has smoothed the wrinkles and simplified the facts that are often taught about the first and, so far, only wartime use of atomic weapons.

“The difficulty of these sort of simple ways of understanding it, or these ways of framing it, the first one is just not historically how people thought about it at the time,” Wellerstein said in a phone interview July 10. “It wasn’t seen as this big deliberation, this big debate. That’s a later framing of it that was put on in order to justify having used the bombs.”