M Harry Truman
Harry S. Truman (1884–1972) was the 33rd President (1945–1953), taking office after FDR’s death in the final months of WWII. He made the momentous decision to use atomic bombs against Japan to hasten the war’s end. Truman then guided the U.S. through the post-war transition, including the Marshall Plan to rebuild Europe, the beginning of the Cold War, the Berlin Airlift, and the Korean War. He also advanced civil rights by desegregating the U.S. armed forces.
Interesting anecdote: Truman’s middle initial “S” is just that – a stand-alone letter. It isn’t an abbreviation for a middle name; rather, it was a compromise to honor both of his grandfathers (Anderson Shipp Truman and Solomon Young) who had names starting with S. Truman often signed the “S” with a flourish, and he once joked it stood for “Shippe” and “Solomon” – but officially, the letter stands for nothing by itself.