These are not literal gates with spikes and moats. Rather, they are the silent, everyday thresholds that, by design or circumstance, become instruments of betrayal. The term first appeared in a fragmented Spanish military treatise from the 16th century, El Arte de la Contravigilancia . The author, Captain Rodrigo de Morales, noticed a strange phenomenon during the Siege of Mons (1572). Defenders inside a fortress would often die not from cannon fire, but from their own exits.
Remember: the enemy is not always the one trying to break in. Sometimes, the enemy is the perfectly polite, familiar door that opens just a little too easily. las puertas enemigo
By J. Navarro