William Shatner

Narrator

Edward Teller

Self - Nuclear Physicist

W.H.P. Blandy

Self - Commander Joint Task Force One (archive footage)

Frank H. Shelton

Self - Nuclear Weaponeer

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)

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)