The foundations of the phrase “fifth columnist” firmly lie in a radio broadcast made by the Nationalist
General Emilio Mola Vidal during the Spanish Civil War
. It was on October the 16th, 1936 when he first used the phrase “una quinta columna” (a fifth column) to refer to the group of General Franco’s Nationalist sympathizers that were secretly working amongst the Republicans
that held the city of Madrid
. This fifth column was so called because it would join the four columns of General Mola Vidal’s troops when they attacked the city.
The members (fifth columnists) of this fifth column, undermined the Republican
government from within, and it is this clandestine and subversive betrayal that has led to the generally accepted definition of fifth columnists as people that are prepared to co-operate with an invading enemy to further its military or political aims. The phrase is, though, commonly used to describe any traitorous insider