Law-of-War Perfidy

AuthorSean Watts
Perfidy and treachery are among the gravest law-of-war violations.
The betrayals of good faith associated with perfidy threaten more than
the immediate, tactical positions of the attacker and victim. Perfidious
betrayals inflict systemic harm on the law of war as a guarantee of
minimally humane interaction. Even a single instance of perfidy can
permanently compromise the possibility of humanitarian exchange
between belligerents.
The remedies for perfidy reinforce the point. In personal,
professional, and international relations, perfidy and treachery provoke
draconian and irreversible reactions. Early professional military codes
prescribed summary death for treacherous correspondence with
enemies.1 Earlier, medieval notions of honor and chivalry sanctioned
unending blood feuds to avenge knights killed by treachery.2 Thomas
Jefferson, the acknowledged author of the American Declaration of
Independence, cited English perfidy among the grievances justifying
full-scale revolt, violent war, and permanent succession from the British
Admittedly, many historical uses of the term have been political
rather than legal. Yet perfidy and treachery4 were still well established
* Associate Professor, Creighton University Law School; Judge Advocate, U.S. Army
Reserve—Reserve Instructor, Department of Law, U.S. Military Academy at West Point.
I am very grateful to Colonel (Retired) David Graham, Commander Paul Walker, U.S.
Navy, and Professor Eric Talbot Jensen (LTC Retired), for especially helpful editorial
1 American Articles of War of 1775, Additional Articles, art. 1 (Nov. 7, 1775);
Massachusetts Articles of War, art. 27 (Apr. 5, 1775); British Articles of War of 1765 §
XIV, art. XIX; Articles of War of James II, art. VIII (1688).
2 Geoffrey Parker, Early Modern Europe, in THE LAWS OF WAR 54 (Michael Howard,
George J. Andreopoulos & Mark Shulman eds., 1994) [hereinafter Howard et al.]
3 Declaration of Independence (1776), available at
18th_century/declare.asp. Jefferson and his co-signers’ allegation of perfidy referred
specifically to the conduct of mercenaries employed by the English. Id. The Declaration
of Independence includes several references to the law of war of the period. Id.; see also
4 Law-of-war commentators have intermittently regarded perfidy and treachery as
synonymous. Lieutenant Colonel Willard B. Cowles, High Government Officials as War
Criminals, 39 AM. SOC. INTL L. PROC. 54, 58 (1945) (asserting “The words ‘treachery’
legal concepts in the early customs and usages of war.5 Originally
grounded in broad, customary notions of chivalry and honorable combat,
the prohibition of perfidy proved an essential aspect of ordered
hostilities. The prohibition of perfidy became much more than a general
sanction of underhanded or dishonorable conduct. Law prohibiting
perfidy proved an essential buttress to the law of war as a medium of
exchange between combatants—a pledge of minimum respect and trust
between belligerents even in the turmoil of war. Indeed, it may be
difficult to conceive of an operative or effective war convention at all
without effective rules against perfidy.
Despite its critical role in sustaining belligerents’ faith in the law of
war, the current legal formula for perfidy shows signs of weakness.
Amid seismic shifts in the conduct, scale, participants, and means of
warfare, States have codified progressively narrower conceptions of
perfidy, ultimately incorporating discrete and narrow legal elements into
the offense. Once a broadly expressed and widely understood principle
for instructing combatants in honorable warfare, the perfidy prohibition
now appears as a narrowly codified legal algorithm better suited to legal
advisors and tribunals than to combatants. As evidence of this trend, this
article identifies and explains three categories of perfidy: simple perfidy;
and ‘perfidy’ are essentially synonymous.”). See also discussion infra and accompanying
notes 127–33.
Exchange, Ltd. 2008) (1737). Van Bynkershoek’s treatise, originally published in Latin,
is thought to have been especially influential in the American Revolution. Id. at v.
Although associated with an exceptionally permissive view of lawful conduct in combat,
Van Bynkershoek specifically disapproved of perfidy. Id. He observed,
Nor ought fraud to be omitted in a definition of war, as it is perfectly
indifferent whether stratagem or open force be used against an
enemy. There is, I know, a great diversity of opinion upon this
subject: Grotius quotes a variety of authorities on both sides of the
question. For my part, I think that every species of deceit is lawful,
perfidy only excepted; not that any thing may not lawfully by done
against an enemy, but because, when a promise has been made to
him, both parties are devested of the hostile character as far as
regards that promise.
Id. at 3 (emphasis in original) (citation omitted); see also 2 ALBERICO GENTILI, DEIURE
BELLI LIBRI TRES 175 (James Scott ed., John C. Rolfe trans., 1933) (1612) (It.) (noting
military leaders were permitted to counter treachery with treachery); PIERINO BELLI, A
Nutting, trans., 1936) (1563) (It.) (noting “faith must be kept with an enemy” and
“deceptions that involve no treachery are allowable”).
prohibited perfidy, and grave perfidy. More than doctrinal monikers,
these categories reveal that the twentieth century’s codification of the
perfidy prohibition converted a popularly and intuitively understood
label for betrayal of trust or confidence into a technically bound term of
art, comparatively divested of much of its customary import and broad
While current expressions of perfidy perhaps facilitate criminal
enforcement in courtrooms, much of the spirit and purpose of the
customary prohibition appears to have been lost. Overall, the price of
doctrinal clarity has been reduced attention and fidelity to good faith
conduct of hostilities critical to humane combat and to sustaining the
law-of-war as a trusted means of communication and interaction between
belligerents. This article argues that through doctrinal narrowing States
have created a perfidy prohibition inadequate to protect the law of war as
a means of good faith and humanitarian exchange between combatants.
An understanding of perfidy that is at once consistent with principled
understandings of the law, protective of minimal concerns of humanity,
and all the while preserves something of the law of war as a system of
minimum good faith between adversaries is highly elusive. Giving effect
to States’ twentieth-century narrowing of the perfidy prohibition leaves
critical, widely-accepted values of the law of war unvindicated. Only
State consensus on a broader conception of prohibited perfidy and
treachery will prevent erosion of enduring law-of war values and the law
of war itself.
To be certain, twentieth-century codifications and refinements of the
law of war have loaned clarity and, by implication, legal legitimacy to
conventions thought to have approached “the vanishing point” of law.6
But whether migration from broad principles to specific prohibitions to
regulate warfare has produced an optimal result is uncertain. This
article’s consideration of law-of-war perfidy will perhaps also serve a
starting point for a more deliberate consideration these competing
methods of international law making and development.
6 Lauterpacht famously employed the phrase, “if international law is, in some ways, at
the vanishing point of law, the law of war is, perhaps even more conspicuously, at the
vanishing point of international law.” Hersch Lauterpacht, The Problem of the Revision
of the Law of War, 29 BRIT. Y.B. INTL L. 360, 382 (1952).

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