Answer:
A President Truman learned of the success of the Manhattan Project
Step-by-step explanation:
American President Harry Truman made the decision to use the devastating atomic bomb on Japan as a direct response to the Pear Harbor attack on American soil.
The direct result of this was that the Japanese gave their unconditional surrender and the war was ended.
However, the indirect result of the decision to drop the atomic bomb was that President Truman learned of the success of the Manhattan project which was the atomic bomb.