+"Fifth Column" describes a clandestine group operating within a nation or entity, secretly assisting its external adversaries. These individuals engage in [Sabotage](/wiki/sabotage) or [Espionage](/wiki/espionage) from within, aiming to destabilize and undermine, often unnoticed until impact. The concept emerged during the Spanish Civil War, signifying hidden sympathizers ready to act.
+## See also
+- [Treason](/wiki/treason)
+- [Subversion](/wiki/subversion)
+- [Infiltration](/wiki/infiltration)