Harry S. Truman mistakes or blunders?

Answer 1

He made many mostly by speaking out on taboo subjects in a frank and folksy manner.

He was a war criminal that had no remorse in dropping Atomic Bombs on the japanese cities of Hiroshima and Nagasaki, just to scare the soviets. Those cities were of no military value, and Truman knew that very well, but his weak character and desire to show off to the world as a macho-man president, took him to sacrifice innocent civilians in the altar of his megalomaniac grandiosity. All his most inportrant generals (Eisenhower, Mcarthur, Marshal, Deleny, etc.) critized Truman'decision of using the atomic bomb to destroy Hiroshima and Nagasaki. Some compared his decision to the worst atrocities of Nazi Germany against the jewish people.