- Grant Withers
- Cpl. Larry Lawrernce
- Adrian Morris
- Sgt. Mack McGowan
- Ann Rutherford
- Frances Schiller
- Robert Warwick
- Col. W. R. Bennett
- George J. Lewis
- Sgt. William Schiller [Chs. 1-4]
- Pat O'Malley
- Capt. Grayson [Ch. 1]
- Victor Potel
- Henchman - Fake Native Chief [Ch. 12]
- Jason Robards Sr.
- Kota
- Warner Richmond
- Metcalf - Henchman
- Robert Frazer
- H.R. Douglas
- J. Frank Glendon
- M.J. Buchanan
- Donald Reed
- Pedro - Henchman
- Max Wagner
- Gibson - Henchman
- Richard Alexander
- Ivan - Henchman [Chs. 1-4, 7-9]
- Tom London
- Miller - Henchman M-90
- Jim Corey
- Karlsson - Henchman
- Ted Adams
- Pete - Pilot Henchman
- Franklin Adreon
- Capt. Holmes [Chs. 7-10]
- William Arnold
- Capt. Henderson [Chs. 1, 8, 10]
- Stanley Blystone
- Crawley - Henchman
- George DeNormand
- Marine [Chs. 7-10]
- Lester Dorr
- Co-Pilot [Ch. 1]
- Grace Durkin
- Miss Martin - Douglas' Secretary [Ch. 1, 3]
- Eddie Parker
- Olson - Marine [Chs. 7-10]
- Frank Reicher
- Wheeler - M-70
- Lee Shumway
- Capt. Drake [Chs. 1, 8, 10]
- Milburn Stone
- Red - Henchman [Ch. 2,4-7,10,11]
- Wes Warner
- Marine [Chs. 7-10]
- Carleton Young
- Doctor [Ch. 4]
