Evaristo Márquez, who played rebel leader José Dolores in the film, was not an actor, but rather a poor villager from San Basilio de Palenque, Colombia, whom director Gillo Pontecorvo discovered while scouting locations in that country. He convinced Dolores to star opposite Marlon Brando, though the studio had originally wanted Sidney Poitier.
The setting of the film is a fictional sugar cane-producing Caribbean island named "Queimada." In the original script, this fictive island was part of the Spanish empire, which would have been a more accurate historical conceit, since Spain, rather than Portugal, was the dominant European power in the Caribbean. The Spanish government of Francisco Franco pressured the filmmakers to alter the script, and since Portugal accounts for a considerably smaller share of international box-office receipts than Spain, the producers did the economically expedient thing by making the Portuguese the bad guys. No Portuguese is actually spoken in the film, but rather various forms of Spanish.
The film's original title was "Quemada" (the spanish word for "burnt"), as the action took place in a Spanish colony. When the Spanish government officially complained and threatened a boycott of the film (objecting to the script's supposedly anti-Spanish bias), Gillo Pontecorvo agreed to alter the setting to a Portuguese island, and the release title became "Queimada" ("burnt" in Portuguese).
Sir William Walker, a real historical figure portrayed in this film by Marlon Brando, was neither British nor knighted. Walker was an American adventurer, and his title of "sir" was one he adopted on his own.
United Artists rapidly lost faith in this film as the budget spiraled out of control. Much to director Gillo Pontecorvo's horror, it was re-edited by an editor who specialized in putting trailers together.
Evaristo Márquez said in an interview (November 1, 2009) that in several occasions, when Marlon Brando refused to act, he was the "peacemaker" between director Gillo Pontecorvo and the legendary actor (Brando).
During a 2003 filmed interview, director Gillo Pontecorvo said that although he and Marlon Brando quarreled during the filming of this film, some years later, Brando offered him a chance to direct a movie about a Native American reservation.