Fifth column

A fifth column is a subversive, clandestine group working from within an organisation or country with the objective of bringing about its downfall. The phrase was coined in a radio broadcast in 1936 by General Emilio Mola, one of Franco’s generals, during the Spanish Civil War (1936-39). Mola boasted that he had four columns of troops to lead against Republican-held Madrid and a fifth column of Nationalist sympathisers within the city.