fifth column

plural fifth columns · alternative 5th column

1. A group of people which clandestinely undermines a larger group, such as a nation, to which it is expected to be loyal.

   True, we have people of the fifth column, and, unfortunately, the sixth column, with us; they have them in every country; but so far in this war the British diplomatic and secret service has not been so successful as that clever, astute brute-man Hitler and his agents.

   1940 September 20, The Advertiser, Adelaide, page 24, column 4

   3 more examples

   The rebels, who in November 1936 had fought to enter and failed, walked in yesterday as troops of the generally recognised Spanish Government, and not a shot was fired at them. The supporters of Franco in the city, the “fifth column” he once spoke of, had been waiting for this moment for more than two years.

   1939 March 29, “Madrid gives itself up to Franco”, in The Guardian, →ISSN

   Subject: A project for the destruction of Monsieur Le Chiffre (alias 'The Number', 'Herr Nummer', 'Herr Ziffer', etc.), one of the Opposition's chief agents in France and undercover Paymaster of the 'Syndicat des Ouvriers d'Alsace', the Communist-controlled trade union in the heavy and transport industries of Alsace, and as we know, an important fifth column in the event of war with Redland.

   1953, Ian Fleming, “Dossier for M”, in Casino Royale, London: Pan Books, published 1955, page 14

   Lloyd George's belief in a revolutionary fifth column [the term hadn't been coined then] driving the strike was replicated on Fleet Street. On October 1 [1919] The Times thundered: "The attempt of the strike leaders to subvert Constitutional government in this country and to starve the nation into acquiescence in their revolutionary designs will be defeated, as other onslaughts have been defeated, by the firmness of the people in defence of its liberties."

   2020 January 2, Conrad Landin, “Strife and strikes in post-war Britain”, in Rail, page 52

2. Used other than figuratively or idiomatically: see fifth, column.