The Secret Invasion

Maj. Richard Mace

Terence Scanlon - Demolition

Simon Fell - Forger

John Durrell - Assassin

Mila (as Mia Massini)

Jean Saval

German Fortress Commandant

Gen. Quadri

Marko - Resistance Leader

Stephana

German Patrol Boat Captain (as Helmut Schneider)

Italian Officer

Captain of Fishing Boat

Partisan Leader

Monk

Wireless Operator

German Naval Lieutenant

Peasant Woman

Sailor Firing Signal Rocket (uncredited)

Yugoslav government officials demanded that Yugoslav Resistance ("Partisan") characters wear red stars on their uniforms. Director Roger Corman tried to stop this, arguing that partisans would not identify themselves to the Nazis in this way, but the Yugoslavs had their own way. However, Corman found a solution to this visual problem--he had them edited out in post-production.

Director Roger Corman said of the changes to the original script, "Initially, the prisoner being held was an atomic scientist, the only man knowing the missing key ingredient in the equations to make an atomic bomb. So by freeing him, the five criminals help unleash atomic warfare. And UA [United Artists] said they liked the idea but not that man. So I changed him to an Italian general who would lead the resistance against the Nazis and thereby facilitate an Allied invasion of Italy. UA wanted them to be full-out heroes with less subtlety than I might have sought. I had wanted them to unwittingly and ironically do something bad on their way to being heroes. But this was the majors, and with a half-million of their dollars at stake, I had a feeling these characters might lack nuance. I knew this was one of the drawbacks to working with the studios--story by committee."

Director Roger Corman once said of this film: "The odd thing about this movie is that it had a very similar plot to an old western of mine, Five Guns West (1955). It also came out before The Dirty Dozen (1967). I've heard stories that the producers of 'The Dirty Dozen' actually postponed production of their film an entire year because they realized that our story-lines were so similar."

At c.25 minutes there is a short close-up of the baby breast-feeding. However the mother's shirt is a different colour and design from the other shots.

Aside from the military uniforms, all clothing worn by both the cast and the extras is current fashion, circa early 1960s.