Berg served as a spy for American intelligence services during World War II.

One of his assignments involved attending a lecture given by German theoretical physicist Werner Heisenberg, with orders to shoot Heisenberg if the lecture led Berg to conclude the Germans were close to a nuclear bomb.

• He spoke several languages and was known for his high intellect.

• He was a relatively average baseball player throughout his career in Major League Baseball, and was better known as "the brainiest guy in baseball".

• After World War II, when the O.S.S. was turned into the C.I.A., Berg continued to occasionally serve in intelligence roles.