What were president Truman's contributions during World War 2?

During World War II, President Harry Truman contributed significantly in several ways. First of all, his courage and resolution in stepping forward to lead the Allies after the death of President Roosevelt (in April 1945) was an initial contribution, which led to no faltering or other weakness in the ongoing war-effort. Secondly, his decision to make use of atomic weaponry in order to bring the war to a quick conclusion was yet another contribution.