The Fifth Column: From the Siege of Madrid to Saddam Hussein's 1979 Purge

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A fifth column is a clandestine group working inside a nation or organization to undermine it for an outside enemy, through sabotage, espionage or disinformation. An Austrian official in Belgrade used a version of the idea in 1906 about Serbian nationalists, but the phrase took hold during the 1936 siege of Madrid in the Spanish Civil War. A telegram from the German chargé d'affaires in Alicante, Hans Hermann Völckers, reported a claim that four Nationalist columns were advancing on the city while a fifth waited inside. The boast is usually attributed to General Emilio Mola, but its origin is murky, and the first major publication came from the communist Dolores Ibárruri in October 1936.

The fall of Norway, Denmark, Belgium, the Netherlands and France in 1940 spread the term worldwide. French premier Paul Reynaud said the bridges over the Meuse had been betrayed, Britain passed the Treachery Act of 1940, and Vidkun Quisling's collaboration made his name a synonym for traitor. After Pearl Harbor, Navy Secretary Frank Knox blamed fifth column work in Hawaii without evidence, a claim that helped lead to Executive Order 9066 and the incarceration of more than 100,000 Japanese Americans. Later regimes used the label to justify purges and repression of minorities.

• Time magazine called fifth column talk a national phenomenon in 1940, and Life ran photo spreads on supposed Nazi agents in American towns.
• Postwar analysis found no organized Japanese fifth column in the Philippines before hostilities.
• In 1979 Saddam Hussein had Muhyi Abdul-Hussein Mashhadi read 68 names to a Ba'ath Party assembly, and 22 of them, including Mashhadi, were executed.
• Communist Bulgaria in the 1980s labeled its Turkish minority a fifth column while forcing name changes.
• After the 2022 invasion of Ukraine, Russian leaders branded antiwar protesters a fifth column acting for the West.