Why Einstein wasn't part of the Manhattan Project even though he convinced President Roosevelt to build an atomic bomb

• Albert Einstein sent a letter in 1939 that helped convinced FDR to launch the Manhattan Project.
• But Einstein was not part of the secretive program run by J. Robert Oppenheimer to develop a nuclear weapon.
• US officials worried Einstein's left-leaning political views made him a security threat.

Albert Einstein played a key role in convincing President Franklin D. Roosevelt to launch the Manhattan Project and develop the world's first atomic bomb. 

But the renowned theoretical physicist never took part in the secret project run by physicist J. Robert Oppenheimer; US officials were worried his left-leaning political views posed a security threat.