Brian Donlevy

Maj. Gen. Leslie R. Groves

Robert Walker

Col. Jeff Nixon

Tom Drake

Matt Cochran

Beverly Tyler

Anne Cochran

Hume Cronyn

Dr. J. Robert Oppenheimer

Audrey Totter

Jean O'Leary

Hurd Hatfield

Dr. John Wyatt

Joseph Calleia

Dr. Enrico Fermi

Godfrey Tearle

President Franklin D. Roosevelt

Victor Francen

Dr. Marre

Richard Haydn

Dr. Chisholm

Jonathan Hale

Dr. Vannevar Bush

John Litel

K.T. Keller

Henry O'Neill

Gen. Thomas F. Farrell

Warner Anderson

Capt. William S. Parsons

Ellen Ross

Waitress

Bobby Jordan

Radioman on Tinian Receiving A-Bomb Message

Jerry Schumacher

Nazi Officer