[dh2022]

And to address your last phrase. I do not know what you mean by Truman did not order Hiroshima, and did not even know about Nagasaki.

But it should be clear that, while Truman delegated authority for picking up targets and dropping the bomb to military and State department, Truman along with the rest of his administration Sec of State Byrnes, Sec of War Stimson, Chief of Staff Gen. Marshall already decided the atomic bomb will be dropped on Japan. When Sec of State Byrnes explicitly warned the Japanese about "prompt and utter destruction" he meant exactly that. [0]

Dropping the bomb was done with Truman's approval.

[0] https://en.wikipedia.org/wiki/Potsdam_Declaration#Terms