The newly formed FBI tracks down exiled Mexican general Enrique Estrada and his secret army to stop him from overthrowing the Mexican government. The Estrada Plot is the first book ever written about the Estrada Conspiracy, the last great "untold story" of the early FBI. During the summer of 1926, exiled general Enrique Estrada organised an underground army in southern California for an all-out invasion of Mexico. From the teeming barrios of Los Angeles to the farm country of the Imperial Valley, hundreds of migrants were recruited for the secret army. The conspirators amassed a stockpile of rifles, machine guns, and ammunition, constructed armored vehicles, and even contracted the manufacture of attack aircraft. At the eleventh hour, after an intense investigation, Estrada's army was captured at the border by a team of federal agents and local lawmen. The Estrada Plot is unlike any previous work about the Federal Bureau of Investigation. General Estrada's attempt to invade Mexico and overthrow its government occurred during the early years of the FBI's transition into a modern law enforcement agency. The characters in the story are a mix of the "old Bureau" and the new, and they often seem larger than life. Lucien Wheeler, special agent in charge of the Los Angeles field office, was a former Secret Service operative who had guarded three presidents. Special Agent Emilio Kosterlitzy, the Bureau's "Mexican expert," was a former Russian naval officer who had led the Rurales, a border patrol in northern Mexico that operated under the maxim "catch them in the act shoot them on the spot." Agent Arthur Hopkins, the leader of the Estrada investigation, was a holdover from the final days of the old West. An ex-U.S. Marshal of the Arizona territory, Hopkins was an anachronism in Director Hoover's new organization. The historical background that led to Estrada's invasion plot is as fascinating as the story itself a little-known religious conflict that erupted in Mexico during the mid-1920s. To eliminate the influence of religion in Mexican life, President Plutarco Elias Calles instituted anti-clerical laws directed against the Catholic Church the country's predominant religion bringing all religious activity under state control. Places of public worship became property of the state, religious clergy were deported, and harsh criminal penalties were imposed for infractions of the anti-religion statutes. In time, public worship would be punishable by the firing squad, and Calles decrees would lead to the Cristero War, which cost ninety thousand Mexican lives. AUTHOR: Bill Mills writes about twentieth-century clandestine operations and espionage history. He is the author of The League: The True Story of Average Americans on the Hunt for World War I Spies and Treacherous Passage: Germany's Secret Plot against the United States in Mexico during World War I (Potomac, 2017). He lives in Concord, Massachusetts. 33 photographs