South of the Border (1939 film)

South of the Border is a 1939 Western film directed by George Sherman and starring Gene Autry, Smiley Burnette, and June Storey. Written by Betty Burbridge and Gerald Geraghty, based on a story by Dorrell and Stuart E. McGowan, the film is about a federal agent who is sent to Mexico to prevent foreign powers from gaining control of Mexican oil refineries and fomenting revolution among the Mexican people.

Soon after, Gene goes to the American Consulate seeking further instructions about his mission. He is informed that Dolores brother Andreo Duncan Renaldo is the pawn of a gang of foreign agents operating on the island of Palmero with the objective of establishing an enemy submarine base that would put an end to Pan American neutrality. The Consul orders Gene to leave for Palermo immediately, using the excuse that he and his men are to help Don Diego Mendoza Frank Reicher, Doloress uncle, with his cattle roundup.On the island of Palermo, Gene and Frog learn that Don Diegos caballeros are in fear of Andreo and his band of revolutionaries. Intercepting a secret code broadcast over the radio, Gene traces the signal to the abandoned oil fields and confirms that enemy agents are plotting to gain control of American oil holdings intending to use them for establishing a submarine refueling base. Gene cleverly allows one of the agents to escape and follows him to the office of Saunders Alan Edwards, the head of the gang of foreign spies. Before he can act, Gene is captured by Saunders, who then leads his men and a convoy of oil trucks to the submarines waiting offshore. ........

Source: Wikipedia