Definition of the word fifth columnist

The term "fifth columnist" originated during the Spanish Civil War in the 1930s. The notion behind the term was that an enemy could infiltrate a society or nation from within and quietly subvert it from the inside out. The first, second, third, and fourth columns referred to the traditional military divisions: the frontline troops, reserves, rear services, and fourth column (the strategic reserve). The Italian fascist leader Benito Mussolini coined the term "fifth column" in 1937 to describe a phrase given to him by an imaginary Spanish Civil War opponent. This imaginary opponent suggested to Mussolini that there was a secret, unseen force (the fifth column) behind the battlefront forces (the first four columns) that could undermine a country's military strength and social order from within. The concept of the "fifth columnist" was especially relevant during the Spanish Civil War, when nationalist troops allied with fascist Italy and Nazi Germany faced a powerful resistance movement supported by the Soviet Union. The "fifth columnist" was seen as a potential threat who could compromise the resistance from within by working to undermine the cause or by gathering information for the enemy. Today, the term "fifth columnist" is still used to describe individuals or groups who work to subvert a nation's interests from within, typically by exploiting divisions or weaknesses in society, institutions, or the political system. The use of this term is an enduring reminder of the insights gained during the Spanish Civil War that the victior in any conflict may still be vulnerable to subversion from the inside.