perfidy

Perfidy is a term in international humanitarian law describing acts that invite the confidence of an adversary with the intent to betray that confidence, in order to injure, kill, or capture. The word derives from Latin perfidia, through Old French and English usage, and has long been used to label treachery in warfare.

In modern law, perfidy is prohibited in international armed conflicts. The clearest formulation appears in Article 37 of Additional Protocol I to the Geneva Conventions, which prohibits acts of perfidy designed to kill, injure, or capture an adversary by exploiting legitimate protections. Perfidy involves deceit that relies on protected status or privileges, such as surrender, status as a prisoner of war, or protection as a wounded or medical person. By contrast, rational, non-protected deception or ruses of war that do not exploit protected status are generally not classified as perfidy and are not necessarily illegal.

Common examples of perfidy include feigning surrender to draw defenders from cover, disguising combatants as civilians or as medical personnel, or using emblems such as the Red Cross or a flag of truce to facilitate an attack. The prohibition rests on the abuse of rights or protections granted to enemies under international humanitarian law.

Enforcement and consequences vary by jurisdiction, but acts of perfidy can constitute war crimes and may be prosecuted by national courts or international tribunals. The concept remains central to discussions of the limits on deception in armed conflict and the protection of combatants and civilians alike.