A fifth column is any group of people who undermine a larger group from within, usually in favor of an enemy group or nation. The activities of a fifth column can be overt or clandestine. Forces gathered in secret can mobilize openly to assist an external attack. This term is also extended to organized actions by military personnel. Clandestine fifth column activities can involve acts of sabotage, disinformation, or espionage executed within defense lines by secret sympathizers with an external force.
Emilio Mola, a Nationalist general during the Spanish Civil War, told a journalist in 1936 that as his four columns of troops approached Madrid, a "fifth column" (Spanish: Quinta columna) of supporters inside the city would support him and undermine the Republican government from within.:126–127 The term was then widely used in Spain. Ernest Hemingway used it as the title of his only play, which he wrote in Madrid while the city was being bombarded, and published in 1938 in his book The Fifth Column and the First Forty-Nine Stories.
Some writers, mindful of the origin of the phrase, use it only in reference to military operations rather than the broader and less well defined range of activities that sympathizers might engage in to support an anticipated attack.[lower-alpha 1]
In the United States at the end of the 1930s, as involvement in the European war seemed ever more likely, those who feared the possibility of betrayal from within used the newly coined term "fifth column" as a shorthand for sedition and disloyalty. The rapid fall of France in 1940 led many to blame a "fifth column" rather than German military superiority. Political factions in France blamed one another for the nation's defeat and military officials blamed the civilian leadership, all helping feed American anxieties. In June 1940, Life magazine ran a series of photos under the heading "Signs of Nazi Fifth Column Everywhere". In July 1940, Time magazine called fifth column talk a "national phenomenon". In August 1940 the New York Times mentioned "the first spasm of fear engendered by the success of fifth columns in less fortunate countries". One report identified participants in Nazi "fifth columns" as "partisans of authoritarian government everywhere", citing Poland, Czechoslovakia, Norway, and the Netherlands. Vidkun Quisling aided the Nazis during the campaign in Norway by proclaiming a Nazi government on the day of the German invasion in 1940, and his name of "quisling" is associated with Nazi collaborators.
John Langdon-Davies, a British journalist who covered the Spanish Civil War, popularized the term "fifth column" by publishing an account called The Fifth Column in 1940. The New York Times published three editorial cartoons that used the term on August 11, 1940. In November 1940, Ralph Thomson, reviewing Harold Lavine's Fifth Column in America, a study of Communist and fascist groups in the U.S., in the New York Times, questioned his choice of that title: "the phrase has been worked so hard that it no longer means much of anything". In the US an Australian radio play, The Enemy Within, proved to be very popular, though this popularity was due to the belief that the stories of fifth column activities were based on real events. In December 1940 the Australian censors had the series banned.
British reviewers of Agatha Christie's novel N or M? in 1941 used the term to describe the struggle of two British partisans of the Nazi regime working on its behalf in England during World War II.
In Frank Capra's 1941 film Meet John Doe, newspaper editor Henry Connell warns political ingenue John Doe about a businessman's plans to promote his own political ambitions using the apolitical John Doe Clubs. Connell says to John: "Listen, pal, this fifth-column stuff is pretty rotten, isn't it?", identifying the businessman with anti-democratic interests in the United States. When Doe agrees, he adds: "And you'd feel like an awful sucker if you found yourself marching right in the middle of it, wouldn't you?"
Immediately following the Japanese attack on Pearl Harbor, U.S. Secretary of the Navy Frank Knox issued a statement that "the most effective Fifth Column work of the entire war was done in Hawaii with the exception of Norway." The widely read columnist Walter Lippmann publicized similar accusations of sabotage on the part of Japanese Americans in his syndicated column on February 12, 1942, titled "The Fifth Column on the Coast."
During the Japanese invasion of the Philippines, an article in the Pittsburgh Post-Gazette in December 1941 said the indigenous Moro Muslims were "capable of dealing with Japanese fifth columnists and invaders alike". Another in the Vancouver Sun the next month described how the large population of Japanese immigrants in Davao in the Philippines welcomed the invasion: "the first assault on Davao was aided by numbers of Fifth Columnists–residents of the town".
The term was soon so widely known that it very quickly appeared in popular U.S. entertainment. Introducing a 1941 newsreel, Meet John Doughboy, the animated character Porky Pig asked any "fifth columnists" in the audience to leave the theater immediately. In Alfred Hitchcock's Saboteur (1942), Robert Cummings asks for help against "fifth columnists" who are conspiring to sabotage the American war effort. The next year in Looney Tunes' Foney Fables, the narrator of a comic fairy tale described a wolf in sheep's clothing as a "fifth columnist". In 1943, an animated cartoon in the Merrie Melodies series was called The Fifth-Column Mouse. Both before and after Pearl Harbor, comic books contained references to the Fifth column.  An example of this is the June 1942 Green Lantern. 
- German minority organizations in Czechoslovakia formed the Sudeten German Free Corps, which aided the Third Reich. Some claimed they were "self-defense formations" created in the aftermath of World War I and unrelated to the German invasion two decades later. More often their origins were discounted and they were defined by the role they played in 1938–39: "The same pattern was repeated in Czechoslovakia. Henlein's Free Corps played in that country the part of fifth column".
- In 1945, a document produced by the U.S. Department of State compared the earlier efforts of Nazi Germany to mobilize the support of sympathizers in foreign nations to the superior efforts of the international communist movement at the end of World War II: "a communist party was in fact a fifth column as much as any [German] Bund group, except that the latter were crude and ineffective in comparison with the Communists". Arthur M. Schlesinger, Jr., wrote in 1949: "the special Soviet advantage—the warhead—lies in the fifth column; and the fifth column is based on the local Communist parties".
- North Koreans living in Japan, particularly those affiliated with the organization Chongryun (which is itself affiliated with the government of North Korea) are sometimes seen as a "fifth column" by some Japanese, and have been the victims of verbal and physical attacks. These have occurred more frequently since the government of Kim Jong Il acknowledged it had abducted people from Japan and tested ballistic missiles.
- Some Israeli Jews, including politicians, rabbis, journalists, and historians, who believe that Israeli Arabs identify more with the Palestinian cause than with the state of Israel or Zionism have referred to them, who compose approximately 20% of Israel's population, as a fifth column.
- Counter-jihad literature has sought to portray Western Muslims as a "fifth column", collectively seeking to destabilize Western nations' identity and values for the benefit of an international Islamic movement intent on the establishment of a caliphate in Western countries. Following the 2015 attack by French-born Muslims on the offices of Charlie Hebdo in Paris, the leader of the UK Independence Party Nigel Farage said that Europe had "a fifth column living within our own countries."
- The term was frequently used by some Russian media during 2014 pro-Russian unrest in Ukraine to describe any form of criticism of Russian policy in Ukraine. Aleksandr Dugin actually came up with a concept of "sixth column" describing those members of Russian elite who do not demonstrate sufficient enthusiasm in supporting the official policy and thus indirectly support the enemy.
In popular culture
- Robert A. Heinlein's science fiction novel Sixth Column (1949) describes the work of a hidden resistance movement fighting an oppressive occupying force of Asians on American soil. The novel includes many references to the Spanish events in which the term originated to contrast what the author considers the traitorous fifth column with the novel's patriotic sixth.
- In the 1983 television miniseries V and the 2009 version of the same material, those visitors who actively side with Earth and undermine the activities of their comrades refer to themselves as the "Fifth Column".
- Andrew Sullivan, a British-American writer and political commentator, labeled American leftists who opposed the Iraq War a "fifth column" in an essay published in The Sunday Times. He later apologized.
- James Ellroy's crime novel Perfidia shows the climate of collective hysteria and racism against the Japanese people in Los Angeles after the attack on Pearl Harbor. The novel narrates the Watanabe family's murder, notoriously associated with the fascist ambiences in LA, that compose the Fifth Column. Their murder is after explained as part of an internal conflict of the Fifth Column.
- Podcast started in 2016 featuring Kmele Foster of Free Think Media, Matt Welch of Reason Magazine, and Michael C. Moynihan of Vice News.
- Demographic threat
- False flag operation
- Front organization
- Sleeper cell
- Alien infiltration
- Madeleine Albright, for example, in a lengthy account of German sympathizers in Czechoslovakia in the first years of World War II, does not use the phrase to describe their actions until she considers their possible response to a German invasion: "Many, perhaps most, of the Sudetens would have provided the enemy with a fifth column".
- James Holland. The Battle of Britain: Five Months That Changed History; May–October 1940. ISBN 9780312675004
- The Fifth Column and Forty-Nine Stories. The Literary Encyclopedia. Retrieved June 24, 2010.
- Albright, Madeleine (2012). Prague Winter: A Personal Story of Remembrance and War, 1937-1948. NY: HarperCollins. p. 102.
- Richard W. Steele, Free Speech in the Good War (St. Martin's Press, 1999, 75-6)
- The New York Times: Delbert Clark, "Aliens to Begin Registering Tuesday," August 25, 1940. Retrieved June 27, 2012.
- Polish Ministry of Information (2014). The German Fifth Column in Poland. Washington, D.C.: Dale Street Books. pp. 3–6. ISBN 9781941656099.
- Tolischus, Otto D. (June 16, 1940). "How Hitler Made Ready: I - The Fifth Column". The New York Times. Retrieved July 7, 2012.
- Barkley, Frederick R. (August 11, 1940). "Nation Shapes Defense against Foes at Home". The New York Times. Retrieved July 7, 2012.
- Thomson, Ralph (November 27, 1940). "Books of the Times". The New York Times. Retrieved April 25, 2015.
- Loeffel, Robert (2015). The Fifth Column in World War II: Suspected Subversives in the Pacific War and Australia. Palgrave. p. 85.
- The Times Literary Supplement, November 29, 1941 (p. 589); The Observer, December 7, 1941 (p. 3)
- Riskin, Robert (1997). McGilligan, Patrick, ed. Six Screenplays. University of California Press. pp. 664, 696.
- Niiya, Brian. "Frank Knox". Densho Encyclopedia. Retrieved August 27, 2014.
- Niiya, Brian. "The Fifth Column on the Coast". Densho Encyclopedia. Retrieved August 27, 2014.
- "80 Japanese Troop Ships Are Sighted Off Luzon (Continued From Page1)". Pittsburgh Post-Gazette. December 22, 1941. p. 7. Retrieved October 30, 2014.
- Curtis, Herbert (January 13, 1942). "Japanese Infiltration Into Mindanao". Vancouver Sun. p. 4. Retrieved October 30, 2014.
- Meet John Doughboy at the Internet Movie Database
- Foney Fables at the Internet Movie Database
- The Fifth-Column Mouse at the Internet Movie Database
- Goodnow, Trischa. The 10 Cent War: Comic Books, Propaganda, and World War II.
- Modell, Martin. Green Lantern.
- Robert G.L. Waite, Vanguard of Nazism: The Free Corps Movement in Post-War Germany, 1918-1923 (1952), 88
- Yale Law School: Nuremberg Trial Proceedings Volume 4, 215, December 20, 1945. Retrieved July 19, 2012
- Thomas G. Paterson, Meeting the Communist Threat: Truman to Reagan (Oxford University Press, 1988), 10
- Arthur M. Schlesinger, Jr., The Politics of Freedom (Heinemann, 1950), 92-3
- "North Koreans in Japan have long been vilified as a communist fifth column" (Hans Greimel, "Test sparks N. Korea Backlash in Japan", Associated Press dispatch, October 24, 2006 )
- "... they hurl accusations against us, like that we are a 'fifth column'." (Roee Nahmias, "Arab MK: Israel committing 'genocide' of Shiites", Ynetnews August 2, 2006)
- "... a fifth column, a league of traitors" (Evelyn Gordon, "No longer the political fringe[permanent dead link]", Jerusalem Post September 14, 2006)
- Akbarzadeh, Shahram; Roose, Joshua M. (September 2011). "Muslims, Multiculturalism and the Question of the Silent Majority". Journal of Muslim Minority Affairs. 31 (3): 309–325. doi:10.1080/13602004.2011.599540.
- Bordelon, Brendan (January 7, 2015). "UKIP's Farage: Multiculturalism Creating 'Fifth Column' in West". National Review. Retrieved January 8, 2015.
- Александр Дугин (May 21, 2014). За Ахметова грудью встала российская шестая колонна (in Russian). Nakanune.ru.
- Robert A. Heinlein, Sixth Column (Gnome Press, 1949), 36: "this would not be a fifth column of traitors, bent on paralysing a free country; but the antithesis of that, a sixth column of patriots whose privilege it would be to destroy the morale of invaders, make them afraid, unsure of themselves." See sffworld.com: Mark Yon, Review of Heinlein, Sixth Column. Retrieved July 23, 2012.
- Noah, Timothy (December 2, 2002). "Gore, Sullivan, and "Fifth Column"". Slate.com.
- Sullivan, Andrew (October 12, 2010). "A Response To A Roast: A "Fifth Column" Apology". andrewsullivan.com.
I won't use this shorthand again. Ditto the shorthand of "fifth column." I have no reason to believe that even those sharp critics of this war would actually aid and abet the enemy in any more tangible ways than they have done already. And that dissent is part of what we're fighting for.
- "The German Fifth Column in Poland" London: Polish Ministry of Info, 1941
- "Fifth Column at Work" by Bohumil Bilek, description of German minority in Czechoslovakia, London, Trinity, 1945
- Robert Loeffel, 'The Fifth Column in World War II: Suspected Subversives in the Pacific War and Australia, (Palgrave, 2015)