President Truman in November 1945
(Public domain image from Truman Presidential Library full size image)
Properly, the "S" in Harry S Truman should have no period after it. "S" is not an abbreviation for a middle name; it is his middle name, itself.
Almost lost to Dewey.
In the final months of World War Two, made the decision to drop the atomic bomb on Hiroshima and Nagasaki, Japan.