- Enrique Lister
- Self - Commander 1st Division Republican Army
- Carlos Romero Giménez
- Self - Commander 5th Division Republican Army
- José Díaz
- Self - Member of Parliament
- Gustav Regler
- Self - German Writer
- Dolores Ibárruri
- Self - Republican Leader
- Manuel Azaña
- Self - President of the Republic
- Martinez de Aragón
- Self - Commander 2nd Division Republican Army
- Commander Martinez de Aragón
- Self (Republican Army)
- Orson Welles
- Narrator (English version) (later replaced by Ernest Hemingway)
- Ernest Hemingway
- Narrator (English version)
- Jean Renoir
- Narrator (French version) / Récitant (voice) (uncredited)
