Humanitarianism & War on TerrorINR 3403 Jessy Abouarab

Humanitarianism & War on Terror
INR 3403| Jessy Abouarab
The first use in English of the term 'terrorism' occurred during
the French Revolution's Reign of Terror, when the Jacobins,
who ruled the revolutionary state, employed violence, including
mass executions by guillotine, to compel obedience to the state
and intimidate regime enemies.
The association of the term only with state violence and
intimidation lasted until the mid-19th century, That’s when it
began to be associated with non-governmental groups
What is Terrorism?
The use of terror is not a new phenomenon,
a means to achieve political ends
but as we know it has recently acquired a new intensity.
In many cases, terrorists deliberately choose targets as a means
of pressurizing governments of the state against certain actions.
So its usually a political message.
2
anarchism
Anarchism, often in league with rising nationalism and anti-
monarchism, was the most prominent ideology linked with
terrorism.

Near the end of the 19th century, anarchist groups or
individuals committed assassinations of a Russian Tsar and
contestably a U.S. President.
In the 20th century terrorism continued to be associated with a
vast array of anarchist, socialist, fascist and nationalist groups,
many of them engaged in 'third world' anti-colonial struggles.
Insert a picture illustrating a season in your country.
3
What changed on September the 11th?
On 9/11, America..
Realized that al Qaeda was more than a criminal threat and
enterprise.
That the network of Al Qaeda and the Taliban posed a
dangerous threat and amassed a capability to attack the US on
its own soil.
That counter-terrorism and anti-terrorism efforts required a
comprehensive use of all US resources – it was not a law
enforcement problem alone.
The Global war on Terrorism
The United States, its allies, and the world recognized that the
threat posed by al Qaeda, the acts perpetrated against the US,
were acts of war…
NATO invoked Article V of the treaty; the collective defense
provision.
ANZUS collective defense provisions invoked.
OAS offers assistance..

Rio Treaty
On October 7 – the United States uses military force against
those who attacked it.
A coalition of more than 40 countries joined the US in
Operation Enduring Freedom (OEF).
OEF remains active as elements of the Taliban and al Qaeda
network attempt to destroy the Karzai government and attack
US forces in Afghanistan.
problems identified with terrorism
Definition:
How widely should the offence be defined?
What do they mean by Political Message
Are the motives and intentions behind the attack relevant?
What is the Relationship between terrorism and Use of force by
state?
What is the Relationship between terrorism and Human rights?
Insert a picture of an animal and or plant found in your country.
The first major concern is that of definition.
how widely should the offence be defined?
for instance should attacks against property as well as attacks
upon persons be covered?
And what do they mean by political message?
Are the motives and intentions of the perpetrators relevant in
making it a terrorist mission?
the relationship between terrorism and the use of force by states

in response is posed
the relationship between terrorism and human rights needs to be
taken into account.
7
Humanitarianism and Rights of Prisoners of War
In armed conflicts, some combatants survive and continue to
fight, some are killed, and some get captured by the enemy.
At Guantanamo – or “GITMO” (written as GTMO) – al Qaeda
and Taliban detainees (and supporters) are detained according
to the laws of war.
The framework of their detention presents unique challenges for
international politics.
Terrorism and Criminality
Congress authorized the use of military force against al Qaeda,
the Taliban, and their supporters for two key reasons:
Criminal approaches are essentially reactive => convict “bad
guys” after they commit a criminal act.
The threats posed by al Qaeda were beyond the ability of the
law enforcement community to handle.
Congress also recognized the inherent right of self-defense for
the United States and the authority of the President, as
Commander-in-Chief, to protect the people of the United States.
9
U.S, Authorization for Military Force

That the President is authorized to use all necessary and
appropriate force against those nations, organizations, or
persons he determines planned, authorized, committed, or aided
the terrorist attacks that occurred on September 11, 2001, or
harbored such organizations or persons, in order to prevent any
future acts of international terrorism against the United States
by such nations, organizations or persons.
THE llNIVE-itSITY O• i I THE UNIVERSITY OF CHICAGO
PRESS JOUR ALS C H I C A G ·O
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JSTOR
The Laws of War, Common Conjectures, and Legal Systems in
International Politics
Author(s): James D. Morrow
Source: The Journal of Legal Studies , Vol. 31, No. S1, Rational
Choice and International
LawA Conference Sponsored by the University of Chicago Law
School (January 2002), pp.
S41-S60
Published by: The University of Chicago Press for The

University of Chicago Law School
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THE LAWS OF WAR, COMMON CONJECTURES,
AND LEGAL SYSTEMS IN INTERNATIONAL

POLITICS
JAMES D. MORROW*
Abstract
The laws of war have a mixed record of limiting violence during
war. I explain
these treaties as the codification of the common conjecture of
an equilibrium of a
game theory model of war. These laws succeed only when the
parties comply on
their own or reciprocal sanctions dissuade parties who are
willing to violate the
agreement. Treaties support reciprocity by specifying when
reciprocal sanctions are
appropriate, by controlling the response to violations outside
the control of state
parties, and by screening out states that are unwilling to abide
by a treaty through
their refusal to ratify it. I discuss the design of the laws of war:
why they are
multilateral and general rather than bilateral and specific to
each war, why treaties
are separated by subject matter, why they devolve responsibility
for individual vi-
olations, and the difficulties in determining how strict these
laws should be.
The twentieth century saw the advent and explosion of the laws
of war,
formal treaties that attempt to regulate military conduct during
wartime. These
treaties have a mixed record of compliance; some, such as bans
on the use
of chemical weapons, have generally succeeded; others, such as

the protection
of civilians in civil wars, have generally failed; and others, such
as the
conventions on prisoners of war (POWs), have been observed in
some cases
and not in others. This paper presents an explanation of how
these treaties
could work and why they fail in some cases. It also explores the
question
of which agreements states are willing to make.
International law must be self-enforcing to be effective.
Successful self-
enforcement of law among states requires either that they must
be willing
to live up to their legal obligations regardless of what others do
or that
reciprocity must deter violations. The laws of war limit violence
in wartime
when states at war observe the treaties they have accepted
through ratification.
* Department of Political Science, University of Michigan, Ann
Arbor. Originally presented
at the conference Rational Choice and International Law at the
University of Chicago Law
School, April 27–28, 2001. I would like to thank the
participants at the conference; their
comments were very helpful in revising the paper. I would
particularly like to thank Saul
Levmore and Eric Posner for their comments.
[Journal of Legal Studies, vol. XXXI (January 2002)]
� 2002 by The University of Chicago. All rights reserved.
0047-2530/2002/3101-0011$01.50

S41
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S42 the journal of legal studies
The combination of reciprocal enforcement and state values is
central to the
success of these treaties and international law generally.
Reciprocal sanctions could fail for three reasons. First, the
treaty might
not be sufficiently specific about what actions are unacceptable,
which leads
to a spiral of mistaken retaliation. Second, violations outside
the control of
the warring parties could be interpreted as intentional violations
of the treaty,
which trigger mistaken retaliation. Third, the sanctions might
not deter de-
liberate violations by a state. A treaty system can reduce the
consequences
of each of these three failures for states that intend to comply
with limitations
on violence.
Treaties address the first problem by detailing what acts are
unacceptable.

The combination of lawful intent and reciprocity can work only
when the
parties share an understanding about what behavior is
unacceptable. Other-
wise, reciprocal punishments could be triggered against a state
that sought
to fulfill its legal obligations. The retaliating state might
understand an act
of the opposing side to be a violation when the opposing state
believed its
action was acceptable under their agreement. The latter state in
turn might
perceive the retaliatory acts of the former state as initial
violations of their
agreement. Specificity in a treaty ameliorates this problem by
producing a
common document that states accept on ratification.
Treaties address the second problem in two ways. The
responsibility to
enforce violations by individual combatants is devolved to
ratifying states;
a state can more easily investigate and punish its own soldiers
than the states
who suffer the crimes of those individuals. The control of
individual vio-
lations limits the possibility that such violations trigger
mistaken retaliation,
even if that control is erratic. Treaties also help to create
common expectations
about the level and type of violations outside the control of
states. Often,
warring states must judge their opponent’s compliance by
inferring intentions
from behavior on the battlefield. Shared expectations assist
warring states in

judging whether the pattern of violations they observe is the
result of indi-
vidual violations or state policy.
Treaties address the third problem by screening out states
unwilling to
comply with a treaty through ratification of that treaty. States
that do not
ratify a treaty generally do not comply with the standards of
that treaty.
Failure by a state to ratify a treaty indicates its likely intention
to violate
that treaty in the event of war. Other states then can anticipate
that state’s
likely violations and attempt to limit their effect.
I argue that treaties, and international law more generally, aid
reciprocal
enforcement of agreements. The dual roles of treaties—to create
a shared
understanding of unacceptable conduct and to screen out those
who will not
comply—are the central points of my argument. I begin with a
general
discussion of the role of shared understandings in game theory.
I review a
series of models that explain how the laws of war work during
wartime. On
the basis of this analysis, I discuss the strategic operation of the
laws of war,
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war and international politics S43
how a shared understanding of unacceptable conduct is central
to compliance
with the standards of those laws, and how ratification of a treaty
helps to
address uncertainty about other states’ intentions by screening
out those states
that do not accept the standard. I then discuss the practical
political problems
of the laws of war from the perspective of my argument. There
are three
problematic areas in treaty formation—differences among states
about the
appropriate standard of conduct, reciprocal enforcement when
states cannot
completely observe the causes of violations, and the need for
agreements to
operate at the individual level as well as the state level —which
must be
appropriately dealt with to successfully restrain violence during
war. I explain
two characteristics of the laws of war, multilateralism and fire
walls—the
division of different issues in the laws of war into separate
treaties—by
examining the incentives of states to make such agreements in
advance of
war. I close with the paradox in this approach to international
law.

I. Treaties as Shared Understandings
Reciprocal enforcement depends on a shared understanding of
what con-
duct is unacceptable and what consequences follow from such
conduct. Not
all possible shared understandings are enforceable. The parties
may not be
willing to carry out reciprocal punishment, that punishment may
be insuf-
ficient to deter violations, or difficulties monitoring the
standard could make
effective reciprocity impossible. Laws of war can be effective
only to the
extent that the parties can enforce them against one another;
they must possess
both the ability and the willingness to make the treaty work.
When the parties can enforce a treaty among themselves, a wide
range of
possible treaties are enforceable. The specific agreement
matters. In the ab-
sence of a shared understanding of which agreement is in effect,
actors may
misinterpret one another’s actions or may respond
inappropriately to others’
acts. International law seeks in part to create such a shared
understanding
among the parties. Treaties codify shared understandings of
what behavior
is unacceptable and what consequences may follow.1
Ratification of a treaty
shows that a state publicly accepts that standard.
Effective law of war requires both a shared understanding and
the ability

of states to enforce the law on one another. Political
institutions, of which
international law is an example, can be thought of as an
equilibrium in a
1 International law at times attempts to create novel agents who
can assist with the enforce-
ment of a shared understanding on conduct. Dispute panels are
one example of such agents.
See Paul R. Milgrom, Douglass C. North, & Barry R. Weingast,
The Role of Institutions in
the Revival of Trade: The Medieval Law Merchant, Private
Judges, and the Champagne Fairs,
2 Econ. & Pol. 1 (1990), for a game-theoretic attempt at
examining the consequences of the
creation of an agent, the medieval law merchant, who collects
and disseminates information
to enhance reciprocal enforcement.
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game.2 An equilibrium requires strategies that are mutual best
replies and a
common conjecture that all are playing their equilibrium
strategies. The
former guarantees that no player wishes to deviate from her

equilibrium
strategy; the latter that all share a common understanding of
how they will
play the game. International law can be thought of as the
codification of the
common conjecture of a specific equilibrium, and the players’
strategies on
that equilibrium path describe the behavior under that law. We
can then
assess how well behavior complies with the standards embodied
in a treaty.
This analysis shifts our attention from studying only the norms
and stan-
dards in a treaty to understanding the political problems of
those norms and
standards in practice. Legal systems, in the sense of how
specific laws are
understood, implemented, and enforced by parties, are central to
the analysis.
Does a shared understanding operate as the common conjecture
of an equi-
librium of military competition during wartime, and what
behavior should
result from that shared understanding?
II. Modeling the Enforcement of the Laws of War
If the laws of war codify the common conjecture underlying an
equilibrium
that describes conduct during wartime, we need to understand
the logic of
such an equilibrium and the range of possible equilibria. The
former explains
how and when an agreement limits violence during wartime; the
latter details

the set of enforceable agreements. This section discusses a
progression of
models of war, the laws of war, and their enforcement during
war. The
conclusions of these models of the laws of war illuminate why
states might
choose to create such agreements in addition to furthering our
understanding
of how they operate in practice. I sketch the logic of these
models rather
than present them formally.3
War can be thought of as a strategic competition over the stakes
in dispute,
such as territory. This competition can be represented with a
war-of-attrition
model where the sides fight over the military balance between
themselves.4
In each round, each state chooses whether to quit or continue
the war and
a battle strategy if it chooses to continue the war. The war
continues until
one side concedes the stakes to the other by quitting.5 If both
sides continue
the war in a round, the combination of their battle strategies
shifts the military
2 Andrew Schotter, The Economic Theory of Social Institutions
(1982); and Randall L.
Calvert, The Rational Choice Theory of Social Institutions:
Cooperation, Coordination, and
Communication, in Modern Political Economy 216 (Jeffrey S.
Banks & Eric A. Hanushek eds.
1995).

3 See James D. Morrow, Strategy, Victory, and the Laws of War
(unpublished manuscript,
Univ. Michigan, Dep’t Pol. Sci. 2002), for formal presentations.
4 For a brief introduction to war-of-attrition models, see Drew
Fudenberg & Jean Tirole,
Game Theory 119–26 (1991).
5 If both sides choose to quit in the same round, we assume that
neither receives the stakes.
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balance from its current value and imposes costs on both sides.6
Each side’s
costs of fighting in a round depend on the current military
balance, with
costs rising as balance shifts against a state, and the battle
strategies of both
sides. Each round can be thought of as one battle in the war, and
the sides
choose their battle strategies in the hope of shifting the balance
in their favor.
A side will quit when it is losing badly enough on the
battlefield, that is,

when the military balance shifts far enough against it that it
prefers to quit
rather than continue to fight. A state’s break point is the value
of the military
balance at which it is indifferent between quitting and
continuing to fight. A
state will quit once the military balance is less favorable than
its break point.
The model views battle outcomes as determined solely by the
interaction
of the sides’ battle strategies. Each side’s battle strategy
specifies not only
battle plans, which are conventionally thought of as military
strategy, but
also details of the employment of troops and weapons that could
affect the
result or costs of the battle. For instance, a battle plan executed
using chemical
weapons is a different battle strategy from the same battle plan
executed
without chemical weapons. Each player’s set of battle strategies
is very large
then because many details of doctrine, deployment, and conduct
on the bat-
tlefield determine the outcomes of battles. Although many of
the battle strat-
egies may differ slightly, they are separate strategies unless
they produce
identical effects against all the strategies of the other player.
The laws of war can be thought of as a prewar agreement by the
sides to
abstain from using certain battle strategies during the war. An
agreement not
to use chemical weapons, for example, merely means that the

sides have
agreed not to use any battle strategy that employs chemical
weapons. Of
course, the agreement does not prevent them from using those
battle strategies
in a war; it merely specifies which strategies are deemed
unacceptable.
A law of war is enforceable when neither side is willing to play
any of
its proscribed battle strategies. Such compliance could occur
because neither
side believes that banned strategies are effective against lawful
ways of
fighting. If the sides believe that banned strategies have
military value, they
still might be able to enforce an agreement through reciprocity,
which is
understood as the abandonment of the agreement after a first
use of a pro-
scribed battle strategy. First use removes the agreed-upon
restraints and leads
to a war in which all battle strategies are available. A side
contemplating
first use of a banned strategy assesses any immediate value
from both the
first use and the long-run consequences of the abandonment of
limits in the
war. In addition, the leader of a state may face audience costs
for his violation
of the prewar agreement.7 Domestic or international audiences
may take
actions against a leader after first use of a proscribed strategy,
reducing his
6 Formally, the range of battle strategies and outcomes is given

by a zero-sum game.
7 See James D. Fearon, Domestic Political Audiences and the
Escalation of International
Disputes, 88 Am. Polit. Sci. Rev. 577 (1994), for the concept of
audience costs.
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willingness to break an agreement. Reciprocity enforces a law
of war when
the combination of long-run consequences and audience costs
exceeds the
short-run gain of first use and so prevents violations.
The overall attraction of violating an agreement to limit
violence can be
assessed by comparing the warring parties’ break points with
the constraints
as opposed to without them. If both break points shift in favor
of one side
without the constraints, this side is more likely to win the war
and so gains
from violating the agreement. If both break points move in
opposite direc-
tions, so that both sides require a higher or lower level of defeat

before
surrendering, the effect of the agreement on the chances of each
side winning
is indeterminate. Compliance with such an agreement is more
likely because
it does not favor one side over the other. As mentioned above,
advantages
from first use could also lead to the breakdown of an agreement
because a
side could find the shift in the military balance from first use
great enough
to shift which side is likely to win. A law of war is more likely
to be observed
during wartime under the following conditions:
1. when neither side would use the proscribed strategies even if
they were
available;
2. when the military benefits of first use are small;
3. when the long-run military effect of the proscribed strategies
does not
favor one side over the other; and
4. when audience costs for violations are large.
The problems of enforcement loom in the desirability of any
agreement
and in the question of which agreements states should be
willing to conclude.
Agreements that cannot be enforced in any case have little
reason to exist
in the logic of the model.8 First and foremost, a formal
agreement helps to
specify which battle strategies are acceptable and which are
unacceptable.
Because the battle strategies in the model detail how the sides

fight as well
as their battle plans, there may only be small differences in
conduct across
many strategies. It could be very important to distinguish these
small dif-
ferences in creating a common conjecture about which strategies
are unac-
ceptable during wartime. For example, is the use of riot-control
agents
(namely, tear gas) illegal under the 1925 Geneva Protocol that
forbids the
use of chemical weapons? This level of detail is necessary to
specify which
battle strategies are unacceptable. Again, states could disagree
on which
precise actions are unacceptable even if they share general
values on proper
conduct during wartime. Legalization here aids the limitation of
violence by
reducing confusion about whether a side has violated an
agreement.
Further, the large number of strategies with small differences
across many
of them suggests that a wide range of agreements that differ
slightly could
8 I understand that others may see value in agreements that
cannot be enforced if those
agreements foster the coalescence of new political forces in
favor of the values in those
agreements. Such considerations are beyond this model and the
discussion in this paper.
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all be enforceable. If an agreement that battle strategies {1, … ,
n} are ac-
ceptable and that battle strategies {n � 1, … , n � k} are
unacceptable can
be enforced, then an agreement that shifts strategy {n � 1} from
unacceptable
to acceptable can probably also be enforced. When there are
multiple equi-
libria, such as the multiple standards that are enforceable here,
the specific
common conjecture determines which equilibrium the players
are playing.
Formal treaties on laws of war specify the standard of proper
behavior out
of the set of enforceable standards. This specificity aids in
compliance be-
tween states that are willing to limit violence during wartime.
The sketch of the model above assumes that the war is fought
under
complete information—the players know one another’s values
for the out-
comes of the game. This common knowledge covers each side’s
value of
the prize—the common source of incomplete information in
war-of-attrition

models—and the costs and results of each pair of strategies.9
The sides do
not differ in their judgments of the efficacy of battle strategies,
and so they
can predict when prewar agreements will be violated. In
actuality, states
differ in their judgments about the desirability of various laws
of war and
they do not know completely other states’ willingness to honor
agreed-upon
standards. In the area of treatment of POWs, for instance, some
states act to
protect POWs, with the effect of encouraging surrender by
enemy troops,
while other states choose to exploit POWs, whom they hold for
information,
labor, or to encourage retaliation on the battlefield and thus
discourage their
own soldiers from surrendering.10 Asymmetric information
about the value
of battle results, both in costs that each side suffers and in the
shift in the
military balance, could reflect these differences in willingness
to comply with
the laws of war.
States facing such uncertainty about their opponent’s
willingness to comply
must judge compliance from reports about conduct on the
battlefield and
behind the lines. These judgments are complicated by
uncertainty about
whether observed violations are the product of a decision by the
opponent
to violate the agreement or individual action contrary to a state
policy. The

former case calls for a reciprocal response; the latter does not.
Indeed, reprisal
in the latter case could lead to a collapse of the agreement when
both sides
9 Readers should be aware that the following discussion is not
based on a formal model,
but rather on an understanding of the strategic dynamics that
commonly result from incomplete
information.
10 See Richard Overy, Russia’s War: A History of the Soviet
War Effort, 1941–1945, at
297–98 (1997), on Soviet use of German prisoners as labor; A.
J. Barker, Prisoners of War
99–100 (1975), on German use of Soviet prisoners as labor;
Ikuhiko Hata, From Consideration
to Contempt: The Changing Nature of Japanese Military and
Popular Perceptions of Prisoners
of War through the Ages, in Prisoners of War and Their Captors
in World War II, at 253 (Bob
Moore & Kent Fedorowich eds. 1996), on Japanese policies
designed to make their own troops
less willing to surrender; and Gerald F. Linderman, The World
within War: America’s Combat
Experience in World War II 128–29 (1997), on how relative
leniency by U.S. forces encouraged
German soldiers to surrender.
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https://surrendering.10
sought to comply. This noise varies with the specific subject of
the agreement.
It is unlikely that individual commanders can use chemical
weapons without
higher authorization, while common soldiers hold the power to
summarily
execute soldiers who are attempting to surrender on the
battlefield.
The models discussed above assume that states have perfect
control of
their militaries, which is contrary to the general discussion in
this section.
Atrocities by individual soldiers can violate state policy to
comply with
existing treaties, which creates both noise and the two-level
problem. This
section draws on models of the problems of reciprocity under
noise and a
two-level problem to discuss how the legal system of the laws
of war ad-
dresses these problems.
Noise complicates the problem of determining when a state
should take
reprisals11 against perceived violations by the other side. Were
those atrocities
a result of state policy or individual violations? A rational
response requires
ignoring low-level violations while responding to more

significant viola-
tions.12 In practice, states create “bright lines” that trigger
retaliation when
crossed. Because observed atrocities could combine state and
individual vi-
olations and the other side is likely to respond in turn to
reprisals, responding
to all violations could unravel the agreement through escalating
reprisals.
When the line is crossed, however, retaliation should be
disproportionate to
the triggering offense. Disproportionate responses restore the
deterrent effect
when states do not retaliate against every violation. How
tolerant of minor
violations the bright line is depends on the magnitude of noise
present on
the issue. Issues that face little possibility of noise, such as
chemical weapons,
have a quick trigger for retaliatory response; issues with a great
deal of noise,
such as POWs, should allow a substantial level of individual
atrocities before
retaliation occurs.
These uncertainties about compliance, both anticipated before a
war and
actual during a war, complicate enforcement. Uncertainty about
the oppo-
nent’s willingness to live up to an agreement is compounded by
uncertainty
about its compliance during the war. As Section III discusses,
decreasing
both of these uncertainties is one of the main reasons for formal
treaties on
the laws of war.

III. Ratification as Screening
Inferring other states’ intentions to live up to a standard in
advance of war
is a deeper problem. Here agreement on a single international
standard could
11 I use “reprisal” in its original meaning of a legal retaliatory
response, as opposed to its
current meaning of a retaliatory atrocity.
12 Edward J. Green & Robert H. Porter, Noncooperative
Collusion under Imperfect Price
Information, 52 Econometrica 87 (1984); George W. Downs &
David M. Rocke, Tacit Bar-
gaining, Arms Races, and Arms Control (1990); and George W.
Downs & David M. Rocke,
Optimal Imperfection? Domestic Uncertainty and Institutions in
International Relations (1995).
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help states separate themselves into those that accept the
standard and those

that do not. The process of ratification signifies acceptance by
the ratifying
state of the specific standards in a treaty. Of course, states
sometimes do
violate treaties that they have ratified, but failure to ratify is
still a clear
signal of a state’s refusal to accept the standards of a treaty.
During World
War II, the failure to ratify the 1929 Geneva Convention on
POWs by at
least one member of a warring dyad corresponds well with death
rates of
POWs held by either member of that dyad and with historians’
descriptions
of the brutality of combat in those dyads.13 Joint ratification
then correlates
with stronger compliance with the standards for treatment of
POWs.
Given that ratification of a treaty does not prevent a state from
violating
that treaty in future wars, why do some states refuse to ratify
treaties on the
laws of war? There are audience costs to ratifying a treaty
cynically, with
the intention of ignoring its conditions. Other states may be
reluctant to make
agreements with states that treat treaty obligations cavalierly,
which creates
an international audience. Governments also answer to domestic
audiences.
Between the world wars, Japan sought to instill in its soldiers a
code of
conduct that equated surrender on the battlefield with dishonor
greater than
death. The Japanese army believed that the fighting spirit of its

soldiers was
the one advantage it had over possible opponents and so
instructed recruits
in this code to induce them to fight to the death.14 Ratifying the
1929 Geneva
Convention would have sent conflicting signals to Japanese
soldiers about
the dishonor of surrendering to the enemy and would have
possibly under-
mined the training regimen. Refusal to ratify can then be in the
interest of
a state that has no intention of following the standards in the
treaty.
Ratification then can operate as a screen on the intentions of
states to
observe the standards of a treaty. Those who do not ratify a
treaty screen
themselves out as being unwilling to live up to the treaty. The
process is
screening as opposed to signaling because states either accept or
reject the
treaty instead of stating publicly their future conduct during
wartime. The
latter form of signaling would not establish a common
conjecture that the
state would follow its stated standard, nor would such
declaration necessarily
provide the level of detail generally provided in a treaty to
specify which
battle strategies were unacceptable. State declaration of intent
also creates
the problem of determining what standard holds when warring
parties have
declared different standards in advance. The ability to state
reservations upon

ratification of a treaty does allow states to signal some of their
intentions
about their future conduct. They can specify possible opponents
against whom
they are not bound by the treaty; they can also specify particular
provisions
of the treaty that they find unacceptable. Because reservations
to a treaty are
13 See James D. Morrow, The Institutional Features of the
Prisoners of War Treaties, 55 Int’l
Org. 971 (2001).
14 Barker, supra note 10, at 122; Hata, supra note 10.
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specific and legally binding, they provide a stronger signal of
state intentions
than a simple statement would.
For the states that intend to comply with the treaty, screening
out likely
violators allows them to have a better idea of whether an

opponent will
violate the standards when a war begins. They may be able to
prepare them-
selves to respond appropriately to reduce possible effects of
first use. Their
creation of a single standard through treaty negotiations
establishes a screen
that could separate out some states that would not live up to the
standard.
Multiple levels of commitment to a treaty would enhance
screening by sep-
arating states into further classes of likely levels of compliance
in the future.
However, such multiple levels of commitment create the
problem of what
standard exists between warring states that accept different
levels. Reser-
vations provide some flexibility to adjust a ratifying state’s
precise com-
mitment without creating such difficulties.
Screening, when successful, divides states into those who intend
not to
comply with the treaty and those who probably will. This
division suggests
another role of common conjectures in the laws of war, in-group
versus out-
group enforcement. If states can separate themselves publicly
into these two
groups, then members of the in-group can act differently toward
members
of the out-group, which makes their shared standard stronger.
For example,
the Chemical Weapons Convention separates states by
ratification and re-
stricts trade in chemical agents and precursors from ratifying

states to non-
ratifying states. This division provides a positive incentive to
ratify the treaty
and accept snap inspections of possible production sites for
chemical weap-
ons. Because almost all industrialized states have ratified the
treaty, states
unable to produce these chemicals themselves have a strong
incentive to join
the in-group to import those chemicals. This mechanism
requires both a
shared understanding of which states are in which group and
what chemicals
are restricted.
IV. The Practical Politics of War
In practice, the laws of war must address three main issues:
variation in
state motivations concerning proper conduct, violations by
individuals as
opposed to state violations, and the difficulty of monitoring
compliance. The
importance of each of these issues varies with the specific issue
addressed
in a treaty. The way a specific agreement works in practice (or
fails to work)
depends on the magnitude of the problem that each of these
issues poses for
that agreement. The practical problems of regulating the use of
chemical
weapons differ from those that exist in the protection of POWs.
States vary greatly in their interest in supporting restrictions on
violence
during wartime. For instance, the United States has generally

tried to uphold
those treaties that it has ratified but will not consider legal
restrictions on
aerial bombardment. State policy on specific restrictions on war
varies with
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the strategic effects of the limitation, a desire to curry favor
with public
opinion domestically or internationally, and the moral stance of
the state.
These variations drive both a problem of distribution about
which standards
to adopt—different states prefer different standards—and a
problem of en-
forcement—some states will not live up to an agreed-upon
standard.
The strategic effects of limiting violence cover a wide range of
reasons
why states support or oppose such agreement in both
negotiations and prac-
tice. Militarily, an agreement may have an asymmetric effect if
it is successful,
such as the restrictions on submarine warfare that advantaged

Great Britain
relative to Germany in the world wars. The side disadvantaged
by that agree-
ment is unlikely to comply. Such asymmetric effects need not
take place on
the battlefield to have military consequences ; states can gain an
advantage
by exploiting POWs as labor, as the Japanese and Nazis did
during World
War II.15 Precisely because such asymmetries are likely to lead
states to
ignore commitments, they pose a particular problem for
enforcement of a
candidate agreement. Even agreements that would be symmetric
in their
effects may be difficult to enforce because neither side wishes
to abandon
its freedom to employ certain acts or weapons. The protection
of civilians
in civil wars is often difficult because both the government and
rebels use
violence against civilians to intimidate them. Some weapons
that cause sub-
stantial collateral damage, such as high-powered artillery, are
seen as too
valuable militarily to be restricted through legal agreement.
States may choose to comply with standards to seek support
elsewhere.
For example, Japan treated Russian prisoners well during the
Russo-Japanese
War in order to attract support from Western nations.16 Often,
the target
audience is domestic. Attempts by the U.S. military to portray
recent bom-
bardments as precise, controlled, and aimed solely at military

targets seek
to prevent a loss of public support for such military action.
Similarly, states
may comply with codes of conduct because their leaders believe
that humane
treatment is moral and appropriate. In some situations,
government leaders
must resist pressure from their own civilians to treat the enemy
more harshly.17
Some states may be unwilling to engage in reciprocal
enforcement of the
laws of war because they believe that they are better off
upholding the
standard no matter what the other side does. For instance, the
United States
and Great Britain were unwilling to respond in kind to Japanese
mistreatment
of POWs. To the extent that there was a reciprocal response, it
came on the
battlefield in the unusual ferocity of combat on Pacific
islands.18
15 Barker, supra note 10, at 99–112.
16 Jonathan F. Vance, Objects of Concern: Canadian Prisoners
of War through the Twentieth
Century 21–22 (1994).
17 See John W. Dower, War without Mercy 53–57 (1986), on
attitudes of U.S. civilians
toward the Japanese during World War II.
18 See Linderman, supra note 10, ch. 4.
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These variations in preferred policy create problems for setting
a single
standard and then for enforcing that standard. A treaty requires
resolving the
distributional problem inherent in selecting a standard. Further,
because no
treaty fully specifies all possible contingencies, states cannot
know the full
consequences of a treaty when it is adopted. This combination
creates a
conflict between distribution and information at the heart of
coordination on
how to cooperate.19 Even if a single standard is codified in a
treaty, some
states may believe they will be better off ignoring the standard.
Such vio-
lations could be opportunistic or premeditated. Japan neither
signed nor rat-
ified the 1929 Geneva Convention on POWs because it already
had policies
to discourage Japanese soldiers from surrendering and viewed
the Geneva
standard with scorn.20 States may be able to deter opportunistic

defections
through reciprocal sanctions, but states committing
premeditated violations
prefer the breakdown of a treaty to compliance.
The laws of war attempt to control both individual and state
behavior. For
many areas of concern, such as the protection of civilians,
controlling the
behavior of individual soldiers on the battlefield is necessary
for effective
limitation of violence. Individual soldiers commit violations on
their own
even if they are contrary to state policy. For other issues, such
as chemical
weapons, use is controlled centrally, reducing the possibility of
soldiers vi-
olating a standard on their own initiative. As pointed out above,
behavior at
the state and individual levels is linked: state violations often
lead to unusual
violence on the battlefield, and large-scale individual violations
can trigger
retaliation by states.
This two-level problem—that treaties must operate on both the
individual
and state levels—creates two issues. First, there will always be
some vio-
lations when the policing of individuals is critical for an issue.
Soldiers
commit crimes against prisoners and civilians even in the best-
disciplined
armies. Perfect compliance cannot be expected. The
management of indi-
vidual violations is generally left to the militaries of those

violators. A vi-
olator’s own military justice system is more likely to be able to
collect the
information to determine what happened and bring the violator
to trial. That
system of devolved responsibility requires active state
participation in dis-
ciplining its own soldiers. State policy can encourage individual
violations
in two ways: active policy to promote atrocities and neglect of
discipline.
The training and discipline of soldiers in the laws of war are
essential for
the limitation of individual violations.
Second, individual violations compound the problem of
determining
whether the other side is complying with a treaty. The
protection of sailors
on the high seas requires that individual ship captains protect
the survivors
19 See James D. Morrow, Modelling the Forms of International
Cooperation: Distribution
versus Information, 48 Int’l Org. 387 (1994).
20 Hata, supra note 10.
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of ships that they sink. However, atrocities on the high seas are
difficult for
the state of the victims to discover simply because there may be
no survivors.
In the absence of public state declarations of policy and intent,
other states
must infer those policies from observed violations. Because
some violations
occur even when state policy supports a treaty and other
violations are hidden
from observation because they occur behind enemy lines,
knowing when to
respond to a pattern of observed violations is difficult.
Individual violations then are a source of the third practical
problem in
reciprocal enforcement: the difficulty of determining whether
the other side
has complied. We can think of this problem as the problem of
inferring a
signal in the presence of noise—that is, inferring state policy
when unintended
violations may occur. Noise creates the possibilities of failing
to retaliate
when you should and of retaliating when you should not. Both
types of error
undermine a standard, the former by reducing deterrent effect,
the latter by
creating reciprocal spirals of atrocities. Because reciprocal
sanctions are often

actions that would be unacceptable under the treaty if they were
not in
response, the shared perception that an act is a violation or
acceptable re-
sponse to a violation is critical to avoiding spirals. Noise
undermines such
shared perceptions of acts.
Noise also arises from acts that are hard to observe. For
instance, POW
camps are behind enemy lines and so not open to direct
observation by the
home state of the prisoners. Further, the detaining power
probably does not
wish to allow observers from the home state to inspect camps
out of the fear
of contact with the prisoners. One solution to such problems is
neutral ob-
servers, and the Red Cross plays that role with respect to POWs
by requiring
states to collect and submit lists of POWs they hold, inspecting
camps, and
delivering mail and packages to POWs. Often the first sign that
a state is
violating the POW standards is its unwillingness to allow the
Red Cross to
visit its camps.21 Other actions cannot be observed so easily by
neutral parties;
observing acts on the battlefield imposes the risk of death on
observers, thus
militaries are the most effective observers of the conduct of
their own soldiers.
Inadvertent acts also create noise. During the Italian campaign
of World
War II, a German bombardment hit an American supply dump of

chemical
weapons and released a cloud of poison gas that drifted toward
the German
lines.22 This cloud could easily have been interpreted as an
illegal chemical
weapons attack by the Germans. The vagaries of battle can
produce outcomes
that can be interpreted as violations of the laws of war.
Practically, a legal system to limit violence during wartime
must reflect
21 During World War II, the United States and Canada inferred
that Japan was not living up
to the 1929 Geneva Convention on POWs on the basis of
Japanese interference with Red Cross
inspections and reports on their POW camps. See Vance, supra
note 16, at 186–88.
22 Jeffrey W. Legro, Cooperation under Fire: Anglo-German
Restraint during World War II
200 (1995).
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and accept the consequences of these three aspects of the laws
of war. Ef-
fective limitation on violence in the face of variation in state
preferences in
standards (or the absence of standards) requires that a standard
be acknowl-
edged in advance and that an answer to state deviations from
that standard
exists. This shared understanding must address what behavior is
unacceptable
and how states may respond to it to produce expectations for a
successful
legal system. The practical politics that arise from that shared
understanding
must deal with both the two-level problem and the difficulty of
enforcing
agreements in the face of noise. To understand these practical
issues, we
must understand how shared understandings and actors’
incentives reinforce
or undermine one another. In short, we need to understand when
a shared
understanding embodies the common conjecture of an
equilibrium.
V. The Design of the Laws of War
The arguments above explain how and why laws of war can
operate
successfully to limit violence. I now turn to the parallel
question of which
agreements can be formed in advance of war. I focus on four
elements of
the system of laws of war: their multilateral nature, their
separation by issues

into different treaties, the devolution of responsibility to each
state for pun-
ishing individual violations by its soldiers, and the strength of
restrictions
on violence. For each of these issues of design, I ask about the
advantages
or disadvantages of these features compared with alternative
arrangements.
My arguments about how these agreements operate in practice
allow an
analysis of the consequences of these alternative arrangements.
Each of these
alternative arrangements has attractive features that are
outweighed by their
disadvantages only when we consider how these arrangements
would work
in practice.
A. Multilateral Treaties
The laws of war are multilateral treaties that are formed far in
advance of
war rather than bilateral agreements that are formed at the
beginning of a
war. Bilateral agreements could be more efficient in the sense
that warring
states could reach a specific agreement that fit their own views
of acceptable
conduct more closely than a multilateral treaty negotiated
before war could.
Bilateral agreements, however, face concerns about how the
laws of war
could shift each side’s chance of winning if that pair of states
were to find
themselves at war. As stated in Section II, limiting the set of
available battle

strategies can shift the break points of both sides in favor of one
side.
Understandably, the side disadvantaged by a bilateral agreement
might refuse
to accept such an agreement, even if both sides would enforce
the agreement
once it was in place. The multilateral agreement has the
advantage of being
negotiated under a veil of ignorance of which wars will be
fought in the
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future.23 States might agree to a general standard in advance of
war because
they anticipate that they are advantaged in some possible wars
even if they
are disadvantaged in others. The multilateral standard also
reduces negotiation
costs compared with a full set of bilateral treaties negotiated in
advance of
war, even given the difficulties of multilateral negotiations.
B. Fire Walls
The laws of war have been negotiated through a number of

separate treaties
that address different issues in the limitation of violence rather
than a single
overarching agreement covering all issues.24 Compliance with
an overarching
agreement might be more likely because violation on one issue,
such as
POWs, could lead to retaliation on another issue, such as
chemical weapons.
The state suffering first use would choose the form of
retaliation that would
produce the greatest strategic benefit to itself. The linkage
between all limits
on war could make reciprocity more effective than separation
into individual
treaties.25 However, the laws of war do not rely on such linkage
across issues.
Instead, the laws of war are negotiated in separate treaties,
creating fire walls
between the issues. A state violation in one area does not allow
the opposing
side to violate some other treaty, and such generalized
retaliation is rarely
threatened.26 The most general sense of a fire wall is the idea
that even
aggressors as defined by the United Nations still receive the
protection of
the laws of war if they are ratifying powers. In the model, fire
walls can be
thought of as separate agreements on sets of banned battle
strategies. A
violation of one agreement opens up only the strategies banned
in that agree-
ment, not those banned by other agreements. Given that some
limits will not
be enforceable in all wars, fire walls allow some limits to

persist even when
others fail. So, for instance, the use of V-weapons to bombard
London by
23 Not surprisingly, potential agreements pushed by some
countries are rarely accepted by
the particular opponents at whom those agreements appear to be
targeted. For example, France
and Germany were unwilling to accept British proposals to limit
submarine warfare against
merchant shipping during the 1920s. Legro, supra note 21, at
36–37.
24 It need not be that all issues would have to be settled in one
treaty for a universal agreement
on the laws of war. New treaties could be added to that
agreement upon their coming into
force.
25 Michael D. McGinnis, Issue Linkage and the Evolution of
International Cooperation, 30
J. Conflict Resol. 141 (1986).
26 The closest example of an explicit breach of a fire wall was
U.S. Secretary of State James
Baker’s threat before the Gulf War to Iraq’s Foreign Minister
Tariq Aziz that the United States
would expand its war aims to include the overthrow of the
regime in Baghdad if Iraq used
chemical or biological weapons. See Lawrence Freedman &
Efraim Karsh, The Gulf Conflict,
1990–1991, at 257 (1993). Violations on the battlefield of one
of the protections of soldiers
trying to surrender, of medical personnel and the wounded, and
of flags of truce often trigger
violations of the others, which effectively breach the fire walls

between these protections. See
Linderman, supra note 10, at 135, 137, & 141 for examples.
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the Nazis did not lead to the use of chemical weapons by Great
Britain,
despite arguments by Churchill to use gas against German
civilians.27
Noise suggests another reason for creating fire walls between
treaties that
cover different issues in the laws of war. Because issues vary in
the level of
noise present, separating enforcement of the treaties from one
another de-
creases the chance that a breakdown on one issue will spread to
another.
Issues that present a high level of noise are more likely to break
down in
practice even if only from misunderstandings. Even if the
system fails on

those issues, other treaties that cover issues with less noise
could still be
sustained. Because noise increases the chance that agreements
will fail in
practice, fire walls that are created by the separation of treaties
help to
preserve some order on the battlefield.
C. Devolution of Responsibility for Individual Violations
The laws of war typically devolve responsibility for individual
violations
to ratifying states to enforce on their own soldiers.
Alternatively, other states
or international bodies could enforce the laws of war against
individual
violators. The International Criminal Court is a first step in the
direction of
creating such an international body.
The two-level problem of policing individual violations of the
treaties
resembles the prevention of the escalation of ethnic violence
that James D.
Fearon and David Laitin model.28 They compare two systems of
response to
violent acts across groups: in the first system, members of each
group respond
to violent acts by a member of the other group by retaliating
against any
member of the other group whom they meet; in the second
system, members
of each group discipline their own violators, and retaliation
across groups is
not allowed. The former system has less deterrent effect than
the latter be-

cause the violators are unlikely to face personal retaliation. It
also has an
increased chance of spiral escalation because the individuals
who suffer
retaliation for the acts of other members of their group are
likely to perceive
a reprisal as a violation. Fearon and Laitin show further that
devolution of
discipline to groups is less likely to collapse in the face of
difficulties in
determining who is responsible for a violation than general
cross-group
retaliation.
General retaliation across armies on the battlefield happens
sometimes,
particularly when it becomes clear that one side is unwilling to
live by an
agreement or police its own soldiers to live up to that
agreement. Combat
during World War II on the eastern front in Europe and in the
island war in
the Pacific was unusually brutal because Russian and American
soldiers
27 Legro, supra note 22, at 164–67.
28 James D. Fearon & David D. Laitin, Explaining Interethnic
Cooperation, 90 Am. Polit.
Sci. Rev. 715 (1996).
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learned about the Nazi and Japanese treatment of POWs and
men who were
trying to surrender and responded with no quarter.29 These
general collapses
of the laws of war are more common in cases such as the
treatment of POWs
and civilians, where noise from individual violations is more
common.
As in the case of ethnic conflict, devolution to states of
punishment of
individual violations by their own soldiers can prevent spi rals
of retaliation
even in the face of noise. An army is more likely than its
opponent to be
able to determine which of its soldiers have committed
atrocities and then
apprehend and punish the violators. After all, the survivors of
an atrocity
are often those who committed the act and their comrades in
arms rather
than the victims. Even when a treaty allows a state to punish
individual
violators from a state at war with it, such as the POW treaty, the
opportunity
is almost never pursued during wartime. The United States, for
instance, did

not carry out capital sentences on German POWs whom it tried
and convicted
of murdering fellow German POWs inside camps in the United
States during
World War II.30 The fear was that the Nazis would retaliate
against an ex-
ecution even of a prisoner justly convicted of a capital offense
while in
captivity. States at war cannot demonstrate to one another that
such trials
are fair, and so the possibility of states trying individual
violators from other
states during wartime is likely to lead to reciprocal spirals
between states
rather than deterrence of individual violations. The devolution
of responsi-
bility for individual violations to states has two advantages:
militaries are
better able to collect information on violations by their own
personnel, and
they have a greater ability to arrest, try, and punish their own
individual
violators than the opposing side or an international body. The
International
Criminal Court recognizes these advantages in its respect for a
state’s policing
of its own citizens when this is effective.
D. Strength of Restrictions
The strength of restrictions in a treaty poses a dilemma for both
screening
and in-group/out-group logic that I have argued are central to
the successful
operation of the laws of war. Both require that ratification not
be universal,

that states divide themselves into different groups through
ratification. A
treaty ratified by all states communicates no advance warning of
which states
intend to violate that treaty. In-group/out-group logic requires a
clear cost to
joining the in-group in order to prevent all states from joining.
Attempts to
make law acceptable to all states by lowering standards
undermine both
screening and in-group/out-group logic. Stronger standards lead
to fewer
states that are willing to accept a treaty, which enhances the
screening effect
29 See Linderman, supra note 10; and Stephen G. Fritz,
Frontsoldaten: The German Soldier
in World War II (1995).
30 Arnold Krammer, Nazi Prisoners of War in America 169–73
(1979).
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and produces a greater limitation on violence among the

ratifying states.
Stronger standards also produce a larger consequence for
joining the in-group
through ratification, which reduces the number of states that
would ratify
cynically to gain the benefits of in-group membership. On the
other hand,
stronger standards discourage some states from joining the
system by ratifying
a treaty, which raises the chance of wars where at least one side
will not
have accepted limits on its behavior during the war. Where the
exact balance
between the benefits and costs of stronger conditions falls is not
easy to
determine, hence the dilemma of the strength of restrictions.
VI. Conclusion: A Paradox
I have argued in this paper that the laws of war operate as the
codification
of a common conjecture within an equilibrium and explored the
consequences
of that argument. I close by noting how this view of
international law poses
a paradox. In game theory, a common conjecture must be
present to use
equilibrium analysis, regardless of the source of that shared
belief. A common
conjecture specifies all possibilities whether they can occur in
equilibrium
or not (up to uncertainties and private information in the game).
The paradox
is this: why is law in the form of treaties necessary if the parties
already
share a complete understanding of possible responses to all

contingencies?
This question challenges the role of customary international
law. Although
custom and existing practice often contribute to the
development of a common
conjecture, law has a specific role to play in specifying how
those customs
should operate. Custom as a guide often lacks sufficient detail
to allow
warring parties to share an understanding of what conduct is
acceptable and
what consequences follow from unacceptable conduct. Formal
negotiation
can sharpen the understanding among states about custom;
formal negotiation
creates common knowledge about which states have accepted
the formal
standard and thus creates an opportunity for screening. Custom
leaves the
answers to these questions unclear.
Shared understandings about limiting violence during wartime
have
worked in the absence of formal international law. For example,
the violence
of sieges from the Middle Ages into the modern era was
regulated by an
informal agreement on the rights and responsibilities of both
parties.31 Once
the fortifications of a city were breached, the besiegers could
call on the
defenders to surrender the city. If they did, their lives and those
of the
residents of the city would be protected. If the defenders chose
to continue

resistance, the attackers were free to do as they wished with
them and the
city if they captured the city by storm. This shared
understanding sufficed
even in the absence of a formal treaty. This practice did lead to
several
31 See Geoffrey Parker, Early Modern Europe, in The Laws of
War: Constraints on Warfare
in the Western World 40, 48–51 (Michael Howard, George J.
Andreopoulus, & Mark R.
Shulman eds. 1994), for a discussion of this practice in early
modern Europe.
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https://parties.31
horrific sacks of cities, notably Magdeburg in 1631 and
Drogheda in 1649,
when the garrison chose to resist. It also reduced the chance of
unnecessary
resistance by reassuring the garrison that quarter would be
extended if it
surrendered after a breach was made. Understandably, questions
arose as to
how large a breach in the walls must be to justify a call for the

garrison to
surrender. Refinement and codification of informal shared
understandings of
appropriate limits on violence are central issues in treaties on
the laws of
war.
The concept of equilibrium in game theory provides no
guidance about
the paradox because it assumes a common conjecture among the
players.
There is nothing for a treaty to clarify about how the standard
operates; it
is simply a matter of choosing a standard. The screening
argument developed
in the paper embodies the game-theoretic idea of common
conjecture under
the conditions of uncertainty about others’ intentions. Each
state has private
information about how it will behave during wartime, and the
treaty operates
to screen out types of states that are unwilling to live with the
common
standard. A treaty exists solely as a public act of establishing
the standard,
and ratification is the public act of accepting that standard.
The screening argument here misses an important element of the
laws of
war in practice. Standards develop over time in response to
wartime expe-
rience. If a common conjecture exists among states, they would
not have to
develop treaty standards over time because they would already
share expec-
tations for all contingencies. There are two separate issues here:

one concerns
unanticipated events and consequences, and the other
contradictory under-
standings of appropriate conduct. Both result from incomplete
understand-
ings.32 These issues could be explored by relaxing the
assumption of common
conjecture to allow for discordant beliefs about what should
happen off the
equilibrium path. Such beliefs could exist in equilibrium if the
anticipations
of both sides about what would happen off the equilibrium path
support
equilibrium behavior. In plain English, neither side believes
that acting out-
side the range of anticipations is in its interest. Development of
a standard
through treaties then could help create common knowledge of
that standard
and its application.
This argument implies that greater legalization is always
preferable. It
helps to eliminate unanticipated situations and reactions.
Despite this argu-
ment, greater legalization may not be beneficial in all cases.
When inter-
national law seeks to establish neutral actors to judge individual
cases, general
principles of law could be superior to highly detailed treaties.
The arbitrators
of a dispute would then apply those principles as is common in
domestic
law in the interest of helping the parties arrive at a common
understanding
of responsibility and appropriate response in the dispute. The

laws of war,
on the other hand, seek to coordinate parties at war when
deliberation on
32 Would these incomplete understandings be “uncommon
conjectures”?
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the appropriate response to violations is probably difficult at
best. Greater
legalization in the laws of war is not attractive when the
candidate treaty
tries to address issues for which an agreement is probably not
enforceable.
That stronger treaty could undermine a weaker system that
succeeds in a
more limited way. Successful shared understandings to limit
violence must
serve as the common conjecture of some equilibrium.
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19:14:54 UTC��

https://��131.94.186.70Structure
BookmarksFigureFigureThe Laws of War, Common
Conjectures, and Legal Systems in International Politics
Author(s): James D. Morrow Source: The Journal of Legal
Studies , Vol. 31, No. S1, Rational Choice and International
LawA Conference Sponsored by the University of Chicago Law
School (January 2002), pp.S41-S60 Published by: The
University of Chicago Press for The University of Chicago Law
School Stable URL:
https://www.jstor.org/stable/10.1086/340810 JSTOR is a not-
for-profit service that helps scholars, researchers, and students
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For more information about JSTOR, please contact .
[email protected]Your use of the JSTOR archive indicates your
acceptance of the Terms & Conditions of Use, available
athttps://about.jstor.org/terms The University of Chicago Press
and The University of Chicago Law School are collaborating
withJSTOR to digitize, preserve and extend access to The
Journal of Legal Studies This content downloaded from on
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use subject to
��131.94.186.70https://about.jstor.org/ter
ms THE LAWS OF WAR, COMMON CONJECTURES, AND
LEGAL SYSTEMS IN INTERNATIONAL POLITICS THE
LAWS OF WAR, COMMON CONJECTURES, AND LEGAL
SYSTEMS IN INTERNATIONAL POLITICS JAMES D.
MORROW* Abstract The laws of war have a mixed record of
limiting violence during war. I explain these treaties as the
codiﬁcation of the common conjecture of an equilibrium of a
game theory model of war. These laws succeed only when the
parties comply on their own or reciprocal sanctions dissuade
parties who are willing to violate the agreement. Treaties

support reciprocity by specifying when reciprocal sanctions are
appropriate, by controlling the response to violations outside
the control of state parties, and by screenin-he twentieth century
saw the advent and explosion of the laws of war, formal treaties
that attempt to regulate military conduct during wartime. These
treaties have a mixed record of compliance; some, such as bans
on the use of chemical weapons, have generally succeeded;
others, such as the protection of civilians in civil wars, have
generally failed; and others, such as the conventions on
prisoners of war (POWs), have been observed in some cases and
not in others. This paper presents an explanation of how
tTInternational law must be self-enforcing to be effective.
Successful self-enforcement of law among states requires either
that they must be willing to live up to their legal obligations
regardless of what others do or that reciprocity must deter
violations. The laws of war limit violence in wartime when
states at war observe the treaties they have accepted through
ratification. * Department of Political Science, University of
Michigan, Ann Arbor. Originally presented at the conference
Rational Choice and International Law at the University of
Chicago Law School, April 27–28, 2001. I would like to thank
the participants at the conference; their comments were very
helpful in revising the paper. I would particularly like to thank
Saul Levmore and Eric Posner for their comments. [Journal of
Legal Studies, vol. XXXI (January 2002)] . 2002 by The
University of Chicago. All rights reserved. 0047-
2530/2002/3101-0011$01.50 S41 This content downloaded from
on Mon, 25 Nov 2019 19:14:54 UTC All use subject to on Mon,
25 Nov 2019 19:14:54 UTC All use subject to
131.94.186.70https://about.jstor.org/terms The combination of
reciprocal enforcement and state values is central to the success
of these treaties and international law generally. Reciprocal
sanctions could fail for three reasons. First, the treaty might not
be sufficiently specific about what actions are unacceptable,
which leads to a spiral of mistaken retaliation. Second,
violations outside the control of the warring parties could be

interpreted as intentional violations of the treaty, which trigger
mistaken retaliation. Third, the sanctions might not deter
deliberate violations by a state. A treaty system can reduce the
consequences of each of these three failures for states that i -
Treaties address the first problem by detailing what acts are
unacceptable. The combination of lawful intent and reciprocity
can work only when the parties share an understanding about
what behavior is unacceptable. Otherwise, reciprocal
punishments could be triggered against a state that sought to
fulfill its legal obligations. The retaliating state might
understand an act of the opposing side to be a violation when
the opposing state believed its action was acceptable under their
agreement. The latter state-Treaties address the second problem
in two ways. The responsibility to enforce violations by
individual combatants is devolved to ratifying states; a state can
more easily investigate and punish its own soldiers than the
states who suffer the crimes of those individuals. The control of
individual violations limits the possibility that such violations
trigger mistaken retaliation, even if that control is erratic.
Treaties also help to create common expectations about the
level and type of violations outside --Treaties address the third
problem by screening out states unwilling to comply with a
treaty through ratification of that treaty. States that do not ratify
a treaty generally do not comply with the standards of that
treaty. Failure by a state to ratify a treaty indicates its likely
intention to violate that treaty in the event of war. Other states
then can anticipate that state’s likely violations and attempt to
limit their effect. I argue that treaties, and international law
more generally, aid reciprocal enforcement of agreements. The
dual roles of treaties—to create a shared understanding of
unacceptable conduct and to screen out those who will not
comply—are the central points of my argument. I begin with a
general discussion of the role of shared understandings in game
theory. I review a series of models that explain how the laws of
war work during wartime. On the basis of this analysis, I
discuss the strategic operation of the lThis content downloaded

from on Mon, 25 Nov 2019 19:14:54
UTC�� All use subject to
ms how a shared understanding of unacceptable conduct is
central to compliance with the standards of those laws, and how
ratification of a treaty helps to address uncertainty about other
states’ intentions by screening out those states that do not
accept the standard. I then discuss the practical political
problems of the laws of war from the perspective of my
argument. There are three problematic areas in treaty
formation—differences among states about the appropriate
standard of conduct, reciprocal enforcemenI. Treaties as Shared
Understandings Reciprocal enforcement depends on a shared
understanding of what conduct is unacceptable and what
consequences follow from such conduct. Not all possible shared
understandings are enforceable. The parties may not be willing
to carry out reciprocal punishment, that punishment may be
insufficient to deter violations, or difficulties monitoring the
standard could make effective reciprocity impossible. Laws of
war can be effective only to the extent that the parties can
enforce them against one another; they must--When the parties
can enforce a treaty among themselves, a wide range of possible
treaties are enforceable. The specific agreement matters. In the
absence of a shared understanding of which agreement is in
effect, actors may misinterpret one another’s actions or may
respond inappropriately to others’ acts. International law seeks
in part to create such a shared understanding among the parties.
Treaties codify shared understandings of what behavior is
unacceptable and what consequences may follow.Ratification o-
1 Effective law of war requires both a shared understanding and
the ability of states to enforce the law on one another. Political
institutions, of which international law is an example, can be
thought of as an equilibrium in a This content downloaded from
on Mon, 25 Nov 2019 19:14:54 UTC�� All
use subject to

ms game.An equilibrium requires strategies that are mutual best
replies and a common conjecture that all are playing their
equilibrium strategies. The former guarantees that no player
wishes to deviate from her equilibrium strategy; the latter that
all share a common understanding of how they will play the
game. International law can be thought of as the codification of
the common conjecture of a specific equilibrium, and the
players’ strategies on that equilibrium path describe the
behavior under that law. We c2 This analysis shifts our
attention from studying only the norms and standards in a treaty
to understanding the political problems of those norms and
standards in practice. Legal systems, in the sense of how
specific laws are understood, implemented, and enforced by
parties, are central to the analysis. Does a shared understanding
operate as the common conjecture of an equilibrium of military
competition during wartime, and what behavior should result
from that shared understanding? --II. Modeling the Enforcement
of the Laws of War If the laws of war codify the common
conjecture underlying an equilibrium that describes conduct
during wartime, we need to understand the logic of such an
equilibrium and the range of possible equilibria. The former
explains how and when an agreement limits violence during
wartime; the latter details the set of enforceable agreements.
This section discusses a progression of models of war, the laws
of war, and their enforcement during war. The conclusions of
these models of the laws of war illuminate why st3 War can be
thought of as a strategic competition over the stakes in dispute,
such as territory. This competition can be represented with a
war-of-attrition model where the sides fight over the military
balance between themselves.In each round, each state chooses
whether to quit or continue the war and a battle strategy if it
chooses to continue the war. The war continues until one side
concedes the stakes to the other by quitting.If both sides
continue the war in a round, the combination of their battle
stra4 5 This content downloaded from on Mon, 25 Nov 2019
19:14:54 UTC�� All use subject to

ms balance from its current value and imposes costs on both
sides.Each side’s costs of fighting in a round depend on the
current military balance, with costs rising as balance shifts
against a state, and the battle strategies of both sides. Each
round can be thought of as one battle in the war, and the sides
choose their battle strategies in the hope of shifting the balance
in their favor. 6 A side will quit when it is losing badly enough
on the battlefield, that is, when the military balance shifts far
enough against it that it prefers to quit rather than continue to
fight. A state’s break point is the value of the military balance
at which it is indifferent between quitting and continuing to
fight. A state will quit once the military balance is less
favorable than its break point. The model views battle outcomes
as determined solely by the interaction of the sides’ battle
strategies. Each side’s battle strategy specifies not only battle
plans, which are conventionally thought of as military strategy,
but also details of the employment of troops and weapons that
could affect the result or costs of the battle. For instance, a
battle plan executed using chemical weapons is a different
battle strategy from the same battle plan executed without
chemical weapons. Each player’s set of battle--The laws of war
can be thought of as a prewar agreement by the sides to abstain
from using certain battle strategies during the war. An
agreement not to use chemical weapons, for example, merely
means that the sides have agreed not to use any battle strategy
that employs chemical weapons. Of course, the agreement does
not prevent them from using those battle strategies in a war; it
merely specifies which strategies are deemed unacceptable. A
law of war is enforceable when neither side is willing to play
any of its proscribed battle strategies. Such compliance could
occur because neither side believes that banned strategies are
effective against lawful ways of fighting. If the sides believe
that banned strategies have military value, they still might be
able to enforce an agreement through reciprocity, which is
understood as the abandonment of the agreement after a first use

of a proscribed battle strategy. First use removes the agreed-
upon rest-7 This content downloaded from on Mon, 25 Nov
2019 19:14:54 UTC�� All use subject to
ms willingness to break an agreement. Reciprocity enforces a
law of war when the combination of long-run consequences and
audience costs exceeds the short-run gain of first use and so
prevents violations. The overall attraction of violating an
agreement to limit violence can be assessed by comparing the
warring parties’ break points with the constraints as opposed to
without them. If both break points shift in favor of one side
without the constraints, this side is more likely to win the war
and so gains from violating the agreement. If both break points
move in opposite directions, so that both sides require a higher
or lower level of defeat before surrendering, the effect of the
agreement on the chances of-1. 1. 1. when neither side would
use the proscribed strategies even if they were available; 2. 2.
when the military benefits of first use are small; 3. 3. when the
long-run military effect of the proscribed strategies does not
favor one side over the other; and 4. 4. when audience costs for
violations are large. The problems of enforcement loom in the
desirability of any agreement and in the question of which
agreements states should be willing to conclude. Agreements
that cannot be enforced in any case have little reason to exist in
the logic of the model.First and foremost, a formal agreement
helps to specify which battle strategies are acceptable and
which are unacceptable. Because the battle strategies in the
model detail how the sides fight as well as their battle plans,
there may only be small differences in c8 --Further, the large
number of strategies with small differences across many of them
suggests that a wide range of agreements that differ slightly
could This content downloaded from on Mon, 25 Nov 2019
19:14:54 UTC�� All use subject to
ms all be enforceable. If an agreement that battle strategies
{1,…, n} are acceptable and that battle strategies {n . 1,…, n .

k} are unacceptable can be enforced, then an agreement that
shifts strategy {n . 1} from unacceptable to acceptable can
probably also be enforced. When there are multiple equilibria,
such as the multiple standards that are enforceable here, the
specific common conjecture determines which equilibrium the
players are playing. Formal treaties on laws of war specify the
standard of proper b---The sketch of the model above assumes
that the war is fought under complete information—the players
know one another’s values for the outcomes of the game. This
common knowledge covers each side’s value of the prize—the
common source of incomplete information in war-of-attrition
models—and the costs and results of each pair of strategies.The
sides do not differ in their judgments of the efficacy of battle
strategies, and so they can predict when prewar agreements will
be violated. In actuality, states differ-9 surrendering.10 States
facing such uncertainty about their opponent’s willingness to
comply must judge compliance from reports about conduct on
the battlefield and behind the lines. These judgments are
complicated by uncertainty about whether observed violations
are the product of a decision by the opponent to violate the
agreement or individual action contrary to a state policy. The
former case calls for a reciprocal response; the latter does not.
Indeed, reprisal in the latter case could lead to a collapse of the
agreemenReaders should be aware that the following discussion
is not based on a formal model, but rather on an understanding
of the strategic dynamics that commonly result from incomplete
information. 9 See Richard Overy, Russia’s War: A History of
the Soviet War Effort, 1941–1945, at 297–98 (1997), on Soviet
use of German prisoners as labor; A. J. Barker, Prisoners of
War 99–100 (1975), on German use of Soviet prisoners as labor;
Ikuhiko Hata, From Consideration to Contempt: The Changing
Nature of Japanese Military and Popular Perceptions of
Prisoners of War through the Ages, in Prisoners of War and
Their Captors in World War II, at 253 (Bob Moore & Kent
Fedorowich eds. 1996), on Japanese policies designe10 This
content downloaded from on Mon, 25 Nov 2019 19:14:54

ms sought to comply. This noise varies with the specific subject
of the agreement. It is unlikely that individual commanders can
use chemical weapons without higher authorization, while
common soldiers hold the power to summarily execute soldiers
who are attempting to surrender on the battlefield. The models
discussed above assume that states have perfect control of their
militaries, which is contrary to the general discussion in this
section. Atrocities by individual soldiers can violate state
policy to comply with existing treaties, which creates both noise
and the two-level problem. This section draws on models of the
problems of reciprocity under noise and a two-level problem to
discuss how the legal system of the laws of war addresses these
problems. -Noise complicates the problem of determining when
a state should take reprisalsagainst perceived violations by the
other side. Were those atrocities a result of state policy or
individual violations? A rational response requires ignoring
low-level violations while responding to more significant
violaIn practice, states create “bright lines” that trigger
retaliation when crossed. Because observed atrocities could
combine state and individual violations and the other side is
likely to respond in turn to repris11 -tions.12 -These
uncertainties about compliance, both anticipated before a war
and actual during a war, complicate enforcement. Uncertainty
about the opponent’s willingness to live up to an agreement is
compounded by uncertainty about its compliance during the
war. As Section III discusses, decreasing both of these
uncertainties is one of the main reasons for formal treaties on
the laws of war. -III. Ratification as Screening Inferring other
states’ intentions to live up to a standard in advance of war is a
deeper problem. Here agreement on a single international
standard could I use “reprisal” in its original meaning of a legal
retaliatory response, as opposed to its current meaning of a
retaliatory atrocity. 11 Edward J. Green & Robert H. Porter,
Noncooperative Collusion under Imperfect Price Information,

52 Econometrica 87 (1984); George W. Downs & David M.
Rocke, Tacit Bargaining, Arms Races, and Arms Control
(1990); and George W. Downs & David M. Rocke, Optimal
Imperfection? Domestic Uncertainty and Institutions in
International Relations (1995). 12 -This content downloaded
from on Mon, 25 Nov 2019 19:14:54
ms help states separate themselves into those that accept the
standard and those that do not. The process of ratification
signifies acceptance by the ratifying state of the specific
standards in a treaty. Of course, states sometimes do violate
treaties that they have ratified, but failure to ratify is still a
clear signal of a state’s refusal to accept the standards of a
treaty. During World War II, the failure to ratify the 1929
Geneva Convention on POWs by at least one member of a
warring dyad corresponds well wof the brutality of combat in
those dyads.13 Given that ratification of a treaty does not
prevent a state from violating that treaty in future wars, why do
some states refuse to ratify treaties on the laws of war? There
are audience costs to ratifying a treaty cynically, with the
intention of ignoring its conditions. Other states may be
reluctant to make agreements with states that treat treaty
obligations cavalierly, which creates an international audience.
Governments also answer to domestic audiences. Between the
world wars, Japan sought to instill in this code to induce them
to fight to the death.14 -Ratification then can operate as a screen
on the intentions of states to observe the standards of a treaty.
Those who do not ratify a treaty screen themselves out as being
unwilling to live up to the treaty. The process is screening as
opposed to signaling because states either accept or reject the
treaty instead of stating publicly their future conduct during
wartime. The latter form of signaling would not establish a
common conjecture that the state would follow its stated
standard, nor would such declaratSee James D. Morrow, The
Institutional Features of the Prisoners of War Treaties, 55 Int’l

Org. 971 (2001). 13 Barker, supra note 10, at 122; Hata, supra
note 10. 14 This content downloaded from on Mon, 25 Nov
2019 19:14:54 UTC�� All use subject to
��131.94.186.70https://about.jstor.or g/ter
ms specific and legally binding, they provide a stronger signal
of state intentions than a simple statement would. For the states
that intend to comply with the treaty, screening out likely
violators allows them to have a better idea of whether an
opponent will violate the standards when a war begins. They
may be able to prepare themselves to respond appropriately to
reduce possible effects of first use. Their creation of a single
standard through treaty negotiations establishes a screen that
could separate out some states that would not live up to the
standard. Multiple levels of commitment to a treaty would
enhance scr----Screening, when successful, divides states into
those who intend not to comply with the treaty and those who
probably will. This division suggests another role of common
conjectures in the laws of war, in-group versus out-group
enforcement. If states can separate themselves publicly into
these two groups, then members of the in-group can act
differently toward members of the out-group, which makes their
shared standard stronger. For example, the Chemical Weapons
Convention separates states by ratification an--IV. The Practical
Politics of War In practice, the laws of war must address three
main issues: variation in state motivations concerning proper
conduct, violations by individuals as opposed to state
violations, and the difficulty of monitoring compliance. The
importance of each of these issues varies with the specific issue
addressed in a treaty. The way a specific agreement works in
practice (or fails to work) depends on the magnitude of the
problem that each of these issues poses for that agreement. The
practical problems of regulating the uStates vary greatly in their
interest in supporting restrictions on violence during wartime.
For instance, the United States has generally tried to uphold
those treaties that it has ratified but will not consider legal
restrictions on aerial bombardment. State policy on specific

restrictions on war varies with This content downloaded from
on Mon, 25 Nov 2019 19:14:54 UTC�� All
use subject to
ms the strategic effects of the limitation, a desire to curry favor
with public opinion domestically or internationally, and the
moral stance of the state. These variations drive both a problem
of distribution about which standards to adopt—different states
prefer different standards—and a problem of enforcement—
some states will not live up to an agreed-upon standard. -The
strategic effects of limiting violence cover a wide range of
reasons why states support or oppose such agreement in both
negotiations and practice. Militarily, an agreement may have an
asymmetric effect if it is successful, such as the restrictions on
submarine warfare that advantaged Great Britain relative to
Germany in the world wars. The side disadvantaged by that
agreement is unlikely to comply. Such asymmetric effects need
not take place on the battleﬁeld to have military consequences;
states can g--15 -States may choose to comply with standards to
seek support elsewhere. For example, Japan treated Russian
prisoners well during the Russo-Japanese War in order to attract
support from Western Often, the target audience is domestic.
Attempts by the U.S. military to portray recent bombardments
as precise, controlled, and aimed solely at military targets seek
to prevent a loss of public support for such military action.
Similarly, states may comply with codes of conduct because
their leaders believe that humanenations.16 -must resist
pressure from their own civilians to treat the enemy more
harshly.17 Paciﬁc islands.18 Barker, supra note 10, at 99–112.
15 Jonathan F. Vance, Objects of Concern: Canadian Prisoners
of War through the Twentieth Century 21–22 (1994). 16 See
John W. Dower, War without Mercy 53–57 (1986), on attitudes
of U.S. civilians toward the Japanese during World War II. 17
See Linderman, supra note 10, ch. 4. 18 This content
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