Einstein Called This His One Great Mistake

In 1939, physicist Albert Einstein wrote a two-page letter warning President Franklin Roosevelt that Nazi Germany might be developing an atomic weapon. The letter launched the Manhattan Project, a two billion dollar top-secret research program that created the first atomic bombs. On August 6, 1945, the bomb named Little Boy was dropped on Hiroshima, followed by Fat Man on Nagasaki three days later. An estimated 200,000 people were killed or injured. Einstein later called his letter the one great mistake in his life and spent his remaining years campaigning for nuclear disarmament.