William Shatner
Narrator
Edward Teller
Self - Nuclear Physicist (as Dr. Edward Teller)
W.H.P. Blandy
Self - Commander Joint Task Force One (archive footage)
Frank H. Shelton
Self - Nuclear Weaponeer (as Dr. Frank H. Shelton)
Dwight D. Eisenhower
Self - U.S. President (archive footage)
Adlai Stevenson
Self - U.S Ambassador (1961-1965) to the UN (archive footage)
Randall William Cook
Newsreel Narrator (archive sound)
Nikolai Bulganin
Self (archive footage)
Winston Churchill
Self (archive footage)
Everett Dirksen
Self (archive footage)
Albert Einstein
Self (archive footage)
Enrico Fermi
Self (archive footage)
Reed Hadley
Self (archive footage)
Averell Harriman
Self (archive footage)
Adolf Hitler
Self (archive footage)
Hubert H. Humphrey
Self (archive footage)
John F. Kennedy
Self (archive footage)
Nikita Khrushchev
Self (archive footage)
Anastas Mikoyan
Self (archive footage)
Marilyn Monroe
Self (archive footage)
J. Robert Oppenheimer
Self (archive footage)
Franklin D. Roosevelt
Self (archive footage)
Dean Rusk
Self (archive footage)
Woodrow P. Swancutt
Self (archive footage)
Leó Szilárd
Self (archive footage) (as Leo Szilard)
Mark Tapscott
Announcer (archive footage)
Paul Tibbets
Self (archive footage)
Wernher von Braun
Self (archive footage)
John von Neumann
Self (archive footage)
Mao Zedong
Self (archive footage)
Roy Neal
Self (uncredited)