Zorro's Fighting Legion is a 1939 Republic Pictures film serial consisting of twelve chapters. It features Reed Hadley as Zorro. The plot revolves around his alter-ego Don Diego's fight against the evil Don Del Oro.
A trademark of this serial is the sudden demise of at least one native informant in each episode. The direction was identical for each informant's death, creating a source of unintentional humor: each informant, upon uttering the phrase, "Don Del Oro is ...", is shot by a golden arrow and dies before being able to name the villain's alter ego. The serial is also unusual in featuring a real historical personage, Mexican President Benito Juárez, as a minor character.
The mysterious Don Del Oro ("Lord of Gold"), an idol of the Yaqui Indians, has emerged and attacks the gold trade of the Republic of Mexico, planning to take over the land and become Emperor. A man named Francisco is put in charge of a fighting legion to combat the Yaqui tribe and protect the gold, but he is attacked by men working for Don Del Oro. Zorro comes to his rescue, but it is too late for him. Francisco's partner recognizes Zorro as the hidalgo Don Diego Vega. Francisco asks Diego, as Zorro, to take over the fighting legion and defeat Don Del Oro. (Source: wikipedia.org)