fifth column is a expression considered synonymous with betrayal, characterized by the meeting of a group of people who act clandestinely with the intention of betraying their fellows, your homeland or your organization.
Originally, the “fifth column” referred to the group of individuals who acted in a given country on behalf of an enemy nation, especially during times of war.
In cases of international wars, members of the “fifth column” could act as both spies and saboteurs, helping the rival country to achieve its military objectives.
Currently, this expression is also used to refer to anyone who helps in the development of clandestine activities related to espionage and sabotage, whether in companies or other corporations, by example.
Learn more about meaning of the civil war.
Origin of the expression "Fifth Column"
The origin of the expression "fifth column" would have arisen during the Spanish Civil War (1936 – 1939), when General Queipo de Llano, using a military formation known as “four columns”, marched towards Madrid and declared that there would be the “fifth column”, waiting for him in the city to greet you.
In this case, the “fifth column” referred to a faction of sympathizers of General Francisco Franco that was infiltrating the Madrid community.
The expression was popularized internationally with the Second World War, when it was used to refer to soldiers who defended the Nazi invasion and their allies, but who belonged to countries that were enemies of Nazi Germany.
As stated, the “fifth column” is not only used to refer to the military, but also to people who, in the in the context of a war, they acted through sabotage and the creation of rumours, in order to “attack from within to outside".