It's not clear what kind of alternative universe history book you're reading, but in this universe Truman did use the atom bomb against Japan.
Atomic not Atomis!
Vice President of the United States.
It was a tough call for the President but he reasoned that he could end the war faster and save the lives of many American service men. The deaths of the military there, helped in that decision.
end WW2
to end the war
President Truman got the order to use them against Japan.
The same day they were ready Truman had the decision. The people were ok with it.
princess patrick harwood President Truman
Harry Truman
The American President, Harry Truman, made the decision to drop atomic bombs on the cities of Hiroshima and Nagasaki.
President Truman.
President Harry S. Truman .