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Thou Shalt Not Kill: Social Psychological Processes and International
Humanitarian Law Among Combatants
Emanuele Castano
Sarajevo School of Science and Technology Daniel Muñoz-Rojas
International Committee of the Red Cross, Geneva, Switzerland
Sabina C
ˇehaji´
c-Clancy
Sarajevo School of Science and Technology
We report findings from an empirical study (N!339) of the attitudes and behavior of combatants from
four conflict-ridden countries (Bosnia-Herzegovina, Georgia, Republic of the Congo, and Colombia) who
were surveyed by delegates of the International Committee of the Red Cross. The study focuses on
violations of international humanitarian law (IHL), with a specific emphasis on violence against other
human beings. Results indicate that having been victim of violence is positively associated with violent
behavior committed in the past, notably by making it more likely for the combatant to be a volunteer in
an armed group, rather than a recruit. Also, status of the combatants (volunteer vs. recruited), having
committed violations in the past, and knowledge of IHL, jointly predict intentions to respect IHL in the
future. Finally, we find that the self-justification processes of demonization of the enemy predicts lower
intention to respect IHL, but high knowledge of IHL can act as a remedy.
Public Significance Statement
Armed conflict and its heavy toll on human life should never happen. But since it does, having rules
of engagement is better than not having them. This set of rules is International Humanitarian Law
(IHL), and it regulates, for instance, who are legitimate targets of violence and the treatment of
prisoners. A better understand of the conditions under which combatants respect these rules is thus
key to reduce the toll of conflict – and to facilitate conflict resolution and the building of a lasting
peace. Among a unique sample of combatants from four different areas of the world, this study
investigates social psychological processes that account for violence, violations of IHL rules and
intentions to respect such rules: the role of being a victim of violence, being a volunteer (vs. a recruit)
in the armed group, having committed violence in the past and the processes deployed to justify such
a violence. These findings, in conjunction with local and historical knowledge of the specifics of a
conflict, may inform policy makers, conflict-resolution practitioners and diplomats, in their efforts to
contain conflict and reduces its negative impact on human life and societies.
Keywords: intergroup violence, victimization, dehumanization, moral disengagement, international
humanitarian law
Editor’s Note. Continue the conversation by submitting your comments
and questions about this article/book review to PeacePsychology.org/
peaceconflict. (The Editor of PeacePsychology.org reserves the right to
exclude material that fails to contribute to constructive discussion.)
EMANUELE CASTANO received his PhD in social psychology. He is a
Professor of Psychology in the Department of Political Science and Inter-
national Relations, Sarajevo School of Science and Technology. His re-
search areas include Cultural Products and Social Cognition, Theory of
Mind and Theory of Society, Morality, Empathy, Collective Identities,
Social Justice, Conflict Resolution and Management, Mediation and Ne-
gotiation, International Relations, Existential Motives of Social Behavior,
and Organizational behavior.
DANIEL MUÑOZ-ROJAS received his PhD in social representation and
communication. He is Deputy Head of Delegation, International Commit-
tee of the Red Cross. His research interests revolve around questions of
social identity and social influence, social discrimination and the role of
threat and norms in intergroup behavior.
SABINA C
ˇehaji´
c-Clancy received her PhD in social psychology. She is
Associate Professor of Psychology in Department of Political Science and
International Relations, Sarajevo School of Science and Technology. Her
interests focus on intergroup reconciliation, group-based emotions, moral
responsibility, intergroup contact, and forgiveness.
WEARE THANKFUL to the many ICRC personnel who contributed to the
data gathering and to the ICRC for its support. We also thank Tali Daniely
and Joel Krim for their help editing and proofreading the paper, and Peter
Kardos, Daniel Bar-Tal, Ned Lebow, and Dario Paez for their useful and
thoughtful comments to earlier versions of this paper.
CORRESPONDENCE CONCERNING THIS ARTICLE should be addressed to Emanu-
ele Castano, Department of Political Science and International Relations,
Sarajevo School of Science and Technology, Hrasni!ka cesta 3a, Sarajevo,
71 000 Bosnia and Herzegovina. E-mail: emanuele.castano@ssst.edu.ba or
emanuele.castano@gmail.com
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Peace and Conflict: Journal of Peace Psychology
© 2019 American Psychological Association 2019, Vol. 1, No. 999, 000
1078-1919/19/$12.00 http://dx.doi.org/10.1037/pac0000410
1
A wealth of theoretical and empirical macrolevel work has been
conducted by social scientists investigating the role of political,
economic, social, and religious factors that lead to large-scale
violence (e.g., Lebow, 2010). These factors influence, and are
influenced by, social psychological processes that are ultimately
responsible for the conduct of violence (e.g., Bar-Tal, 2013; Sherif,
1966; Staub, 1992; Tajfel, 1982). For instance, an essentialized
perception of the other and its infrahumanization (Leyens et al.,
2000; Yzerbyt, Estrada, Corneille, Seron, & Demoulin, 2004) can
quickly turn into a blatant dehumanization when fueled by political
discourse or the need to justify in-group negative behavior (Cas-
tano & Giner-Sorolla, 2006; Castano, Leidner, & Slawuta, 2008),
and is associated with intergroup violence (e.g., Dower, 1987;
Fussell, 1989; Keen, 1986).
Valuable insights about these mechanisms emerge from empir-
ical research that, instead of relying on convenience samples or
university students, has focused on actual combatants in the very
many areas of the world that were experiencing violent armed
conflict or had experienced it in the recent past. Some have used
in-depth interviews or focus groups and have helped in elucidating
the role of ideology among demobilized combatants in Columbia
(Ugarriza & Craig, 2013) and identifying different “types” of
combatants based on interviews with leaders, combatants, wit-
nesses, and victims in Nigeria (Barrett, 2011). Other studies have
taken a more “quantitative” approach, investigating, for instance,
how the perpetuation of violent acts fosters an appetite for aggres-
sion among combatants (Meyer-Parlapanis et al., 2016).
This article also focuses on the behavior of combatants, and
reports findings from structured interviews conducted by delegates
of the International Committee of the Red Cross (ICRC) among
combatants that were engaged in acts of war/violent intergroup
conflict. Given the ICRC’s focus on international humanitarian
law (IHL; Di Lellio & Castano, 2015),
1
the main focus of the
empirical investigation was on IHL-relevant behavior. Such be-
haviors are violent in nature and thus their investigation is useful
to better understand general violent intergroup behavior that is not
sanctioned—for instance, lawful killing in war. This study aimed
at identifying predictors and correlates of violent past IHL viola-
tions (involving harm to another human being, as opposed to, say,
looting of a house) and of intentions to respect IHL in the future.
Accounting for Past Violations
A first aim of this paper is to investigate the relationship
between past victimization and violence. We hypothesized that a
predictor of violent violations is perceived or experienced victim-
ization: the “self-perception of having been the target, either mo-
mentarily or over time, of harmful actions emanating from one or
more other persons” (Aquino & Byron, 2002, p. 71). Individuals
themselves need not be the actual victim of violence to develop a
sense of victimhood; they can do so by virtue of their shared
identity (national, religious) with the actual victims (Noor, Brown,
& Prentice, 2008; Shaw, 2003). This collective victimhood can
have positive effects on intergroup relations if it is inclusive,
namely, if group members recognize others as victims as well
(e.g., Cohrs, McNeill, & Vollhardt, 2015; Vollhardt & Bilali,
2015). In its exclusive form, however, collective victimhood has
highly detrimental effects on intergroup relations, triggering a
pattern of revenge and violence (Bies, Tripp, & Kramer, 1997;
Skarlicki & Folger, 1997) and boosting anger and resentment
toward the perpetrator. This, in turn, may give high moral ground
to the (collective) self, for instance by typecasting it as a moral
patient (Gray & Wegner, 2009). Analyses of the Israeli-Palestinian
conflict, as well as the Balkan Wars of the 1990s, offer some
powerful insights on how this sense of collective victimization that
is exclusive to the ingroup prompts a cycle of violence, notably
because it fosters both preventive and revengeful acts (for a
review, see Bar-Tal, Chernyak-Hai, Schori, & Gundar, 2009).
If the feeling of being a victim by virtue of one’s social identity
can create such powerful feelings and lead to violent behavior,
being an actual victim of violence might be an even stronger
predictor of negative intergroup relations and violent intergroup
behavior (cf., Kreidie & Monroe, 2002). Research has produced
mixed findings in this regard. As cogently argued by Vollhardt
(2009), suffering can lead to altruism and have a positive impact
on intergroup reconciliation. Consistently, data from Rwanda and
the Eastern Democratic Republic of Congo show that personal
victimization can reduce social distance and increase social inclu-
sion (Vollhardt, 2009). Other studies, however, have shown a
negative impact of direct victimization. On a large, multicountry
sample of countries that have experienced violent intergroup con-
flict, Elcheroth (2006) found that being a victim of violence is
positively associated with acceptance of transgression (of the law)
and with anomy. Similarly, in Israel, Canetti-Nisim, Halperin, Sharvit,
and Hobfoll (2009) fond that having direct experience of terror
enhances psychological distress and a sense of threat, which, in
turn, result in more exclusionist political attitudes (see also Myers,
Hewstone, & Cairns, 2009). None of these studies, however, has
looked at the relationship between victimization, level of violence
committed in the past, and intentions about future violent behavior,
amid actual combatants. The context of our study allows us to look
at the effect victimization stemming from actual experience of
violence amid people who are combatants themselves. In this
context, we expect actual experiences of victimization to be asso-
ciated with negative intergroup behavior such as violations of IHL.
Victimization causes physical and psychological suffering, and
particularly the latter is likely to impact, among other things, on
attitudes and behavior toward outgroups, the ingroup and the
overall conflict (e.g., Cárdenas, Páez, Rimé, Bilbao, & Asún,
2014). For instance, victimization may lead to fear, withdrawal,
and perhaps even learned helplessness, and these mental states
could thus push individuals away from violence altogether or even,
as noted above, to develop more positive intergroup attitudes
(Vollhardt, 2009). If this were the prevalent reaction, we expect to
find either no relation between victimization and the status of the
combatant, namely, whether he is a recruit or a volunteer in the
army/armed group, or an inverse relation: the more victimization,
the less likely for the respondent to be a volunteer.
Victimization, however, may foster anger, outrage, and a desire
for revenge and thus have a mobilizing role (Bar-Tal & Hammack,
1
IHL is the law that regulates the conduct of armed conflicts (jus in
bello). It is comprised of several conventions (the Geneva Conventions and
the Hague Conventions), and treaties, case law, and customary interna-
tional law. Generally speaking, IHL is a set of rules that seek, for human-
itarian reasons, to limit the effects of armed conflict. It protects persons
who are not or are no longer participating in the hostilities and restricts the
means and methods of warfare.
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2CASTANO, MUÑOZ-ROJAS, AND C
ˇEHAJIC
´-CLANCY
2012), increasing the likelihood that people would volunteer to
fight the group who victimized them and their ingroup. In addition
to following from a desire to redress injustice (Chernick, 2003) and
to combat a threat to physical and symbolic annihilation via the
reaffirmation of one’s collective identity (Castano, 2004a; Cas-
tano, Yzerbyt, Paladino, & Sacchi, 2002) joining the collective
struggle can have mental health benefits: among Palestinians from
Gaza and the West Bank, increased militancy (against Israel) was
associated with less depression, posttraumatic stress disorder, and
suicidality (Kira et al., 2011). Given that participants in our study
were combatants, who almost, by definition, have not withdrawn
from the conflict, we hypothesize that, at least among this popu-
lation, victimization will predict extent of violent past behaviors.
In addition, we expect actual experiences of victimization to pre-
dict the likelihood of combatants being volunteers (as opposed to
recruits). If victimization predicts whether a combatant is a vol-
unteer or not, volunteering may, at least in part, account for the
expected effect of victimization on the extent of past violent
behavior carried out by the respondent. This conjecture is in line
with findings from research on trauma and violence, and specifi-
cally on appetitive aggression, “a rewarding perception of the
perpetration of violence” (Weierstall, Haer, Banholzer, & Elbert,
2013; p. 505). In a sample of mostly former combatants from
Burundi, Augsburger et al. (2017) found that appetite for aggres-
sion is predicted by lifetime self-committed violence and (among
males) by having experienced traumatic events (see also Weierstall
& Elbert, 2011).
Intentions to Respect IHL
A second aim of this paper is to predict intentions to respect IHL
and engage in future violent behavior. We hypothesize that past
violent behavior (which constitute IHL violations) predicts inten-
tions to respect IHL in the future (Ajzen & Fishbein, 1980). We
further expect intentions to respect IHL to be predicted by knowl-
edge of IHL. Norms affect behavior (e.g., Cialdini, Reno, &
Kallgren, 1990; Manstead, 2000), and it is thus reasonable to
expect that knowledge of the norms that regulate conflict (IHL
knowledge) predicts intentions to behave in accordance to such
norms. Discussion with ICRC delegates suggested a third variable
should also be related to intentions to respect IHL: status of the
combatants. Although reasons for volunteering are many and may
vary from one context to another, compared to recruited combat-
ants, volunteers may have greater practical, symbolic, and emo-
tional stakes in the conflict. As pointed out above, we expect them
to be more likely to have suffered from violence themselves. We
thus believe that intentions to respect IHL may also be lower
among volunteers than among recruits. In this regard, too, research
on appetitive aggression provides important insights. Amid mem-
bers of the Congolese armed forces it was found that appetite for
aggression is positively predicted by the extent of violence one has
perpetrated in the past and by the status of the combatants: vol-
unteers display greater appetite for violence compared to those
who had been forced to join (Weierstall et al., 2013).
Violence and Self-Justification
A third aim of this paper is to shed light on the role of
self-justificatory mechanisms deployed by individuals who report
having committed violations in the past, in accounting for inten-
tions to respect IHL in the future. Self-justificatory processes help
maintain and reestablish positive self-evaluation, integrity, and
equanimity (Steele, 1988). Foremost among the self-justificatory
processes is simple denial (Cohen, 2001), but the palette of justi-
fications available to the individual is much broader. Bandura
(1990) calls these practices, strategies of moral disengagement,
among which we find advantageous comparisons (“They did
worse things to us”) and euphemistic labeling (the use of the term
“collateral damage” to indicate killing of innocent civilians). In the
context of intergroup conflict research has shown the important
role of dehumanization (Dower, 1987; Fussell, 1989; Grossman,
1995; Keen, 1986; Kelman, 1973; Staub, 1987, 1990) as both
predictor and consequence of intergroup violence (Castano &
Giner-Sorolla, 2006; C
ˇehaji´
c, Brown, & Gonzalez, 2009; Coman,
Stone, Castano, & Hirst, 2014; Leidner, Castano, & Ginges, 2013).
Similarly, work on intractable conflicts (Bar-Tal, 1998; Boulding,
1989) has discussed the interplay of animosity and delegitimiza-
tion of the other, which allows them to explain the violence that
they perpetrate and the development of a sense of entitlement, if
not moral duty, to kill them (Bar-Tal, 1990, 2000; Bar-Tal, Avra-
hamzon, Sibley, & Barlow, 2016; Bar-Tal & Hammack, 2012;
Castano et al., 2008; Reicher, Haslam, & Miller, 2014). We
subsume these concepts under the umbrella term of demonization
of the enemy (Castano, 2011; Giner-Sorolla, Leidner, & Castano,
2012) that we measure with a series of items (e.g., “I believed this
was a way of overcoming evil”) alongside less elaborate strategies
such as displacement of responsibility (e.g., “i was drunk”) and
obedience (“I was just doing my job). The latter has long been
shown to be a justification that individuals give for perpetrating
violence against others, as shown in the famous experiment by
Milgram (1974), in which participants willingly delivered danger-
ously high electrical shocks to another participant in a learning
experiment. (The other participant was, of course, a confederate,
and the shocks were not real, unbeknownst to the participants.)
Obedience seems to be a particularly likely self-justification
method among soldiers, who are embedded in a strict hierarchy,
and are routinely obeying orders from their superiors.
Method
Participants
Three hundred thirty-nine participants were combatants from
four different countries that experienced violent conflict at the time
of data collection (year: 1999) or had been involved in such
conflict in recent times. Given the difficulty of collecting such a
data, this Nsimply the maximum number of participants that the
ICRC delegates were able to recruit in the amount of time they
could allocate to the research project, given their other commit-
ments. The limited Nis adequate to conduct the analyses we report
below. Of the 339, a total of 17 participants were not included in
the analysis because of missing values on all the variables ana-
lyzed and reported below, leaving an Nof 323. Bosnia-
Herzegovina (98), Georgia (89), Republic of the Congo (82) and
Colombia (54). The Communication Department of ICRC re-
viewed and approved the content of the questions and the research
protocol in light of its humanitarian mission and its ethical code of
conduct, and assured anonymity and confidentiality to the inter-
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3
VIOLENCE, DEHUMANIZATION AND IHL AMONG COMBATANTS
viewees. Table 1 reports means and standard deviations for the
pertinent variables (described below), for the four countries.
Procedure and Material
Data were obtained via structured interviews conducted by
ICRC delegates. Respondents answered questions orally and in-
terviewers noted their responses. Interviews were conducted in the
native language of the combatant. Given the nature of the ques-
tions asked to participants social desirability could have played a
role. Four features of the data collection aimed at minimizing its
possible impact. Participants: (a) were repeatedly told that their
responses, which were of course confidential, had no bearings on
any action that the ICRC would take in that context; (b) were also
told about the importance of providing spontaneous and truthful
answers, and this was stressed by the interviewer during the
interview; (c) were not paid to participate, in order to minimize the
motivation to please the interviewer/ICRC so to receive the money
and to think that socially desirable answers could lead to them
being further contacted and paid for other interviews; and (d) after
being introduced to the survey and explained the goals, partici-
pants were asked if they wished to continue or not, and it was made
clear that there was no pressure to continue. Here, we focus on a
subset of variables.
Violent victimization was measured by asking participants
whether they had endured a series of 12 hypothetical events.
Respondents’ answers were coded as 1 (yes)or0(no). A factor
analysis was computed on these items, which resulted in two
factors accounting for (27% and 19% of the variance). Four items
loaded onto a factor that referred to violence against property (e.g.,
“Has your home been looted?”) and four loaded onto a factor that
referred to violence experienced by the self (e.g., “Have you been
tortured?”). Remaining items had noninterpretable loadings. Given
our focus, a composite score was computed for the items referring
to violence against the self (see bolded items under Victimization
in the Appendix), to which we refer as violent victimization (M!
.12; SD !.24; Cronbach’s alpha !.74). Since this variable was
skewed (3.17) and attempts to normalize were unsuccessful it was
decided to create an additional, dichotomous variable, by assigning
0 to respondents who reported never being a victim of violence and
1 to those who reported at least one event.
Combatant status. Respondents were asked whether they had
been recruited (100), volunteered (211), or forced to join the
army/armed group of which they were a part (12). The 12 respon-
dents reported having been forced to join were eliminated from the
analysis when the variable was used.
Past violations of IHL. Participants were asked about their
past behavior as combatants. The question “Have you done any of
the following while a combatant, or do you know any other
combatant on your side who has?” was followed by 11 items (see
the Appendix). Respondents indicated whether they, somebody
they knew, or neither had performed any of these behaviors. We
focus here exclusively on responses about the respondents’ behav-
ior, coding for the presence or absence of the behavior. Seven of
these items referred to violent behavior perpetrated directly against
a person (e.g., killing a captured enemy combatant, attacking a
hospital or a member of the Red Cross, torturing a prisoner), while
four referred to less violent behavior (e.g., forcing someone to
leave his home; looting or destroying a house). Similarly to what
was done for the variable victimization, we focused on violations
of IHL perpetrated directly against a human being, and created a
score for past violations committed by the respondent by averaging
the corresponding seven items (see bolded items under Violent
Past Violations in the Appendix). This score, named “violent past
violations,” could vary between 0 and 1 (M!.05, SD !.13;
Cronbach’s alpha !.88). Since this variable was also severely
skewed and attempts to normalize were unsuccessful an additional,
dichotomous variable was created, by assigning 0 to respondents
who reported not having committed any act of violence and 1 to
those who reported having committed at least one
Self-justification. Participants who reported having commit-
ted violations of IHL were further asked why they did so. They
were presented with 11 choices and could indicate whether each
one of them applied or not. Factor analyses revealed that items
loaded into three factors. The first factor, accounting for 30% of
the variance, was labeled “displacement of responsibility,” the
second factor (15%) “demonization,” and the third (10%) “obedi-
ence” (see items under Justification in the Appendix). Scores were
thus created by averaging participants’ responses to these catego-
ries. These scores could vary between 0 and 1 (displacement of
responsibility, M!.33, SD !.34, Cronbach’s alpha !.74;
demonization, M!.46, SD !.38, Cronbach’s alpha !.75;
obedience (single item), M!.57; SD !.49). Because only
combatants who reported having committed violations had justi-
fication scores, the sample for analyses involving these variables
was smaller (N!88).
Table 1
Descriptive Statistics by Country
Bosnia Herzegovina Colombia Republic of the Congo Georgia
Variable M SD "M SD "M SD "M SD "
Past violations of IHL .01
a
.08 .92 .10
be
.17 .86 .08
cef
.17 .80 .05
af
.10 .91
Violent victimization .12
a
.24 .73 .15
a
.23 .72 .09
a
.20 .63 .15
a
.28 .82
Intentions to respect IHL 3.18
a
.58 .79 2.91
b
.62 .71 3.26
a
.69 .68 2.99
b
.54 .63
Knowledge of IHL .85
a
.22 .70 .71
b
.34 .84 .83
ac
.21 .56 .75
bc
.24 .65
Displacement of responsibility .44
a
.43 .71 .17
bc
.21 .50 .5
ad
.30 .66 .25
acd
.39 .57
Demonization .53
a
.51 .95 .43
a
.35 .59 .49
a
.37 .73 .44
a
.44 .87
Obedience .78
a
.44 .73
ab
.44 .47
ac
.51 .45
ac
.51
Note. IHL !international humanitarian law; "!Cronbach’s alpha. Means with different subscripts differ at p#.05.
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4CASTANO, MUÑOZ-ROJAS, AND C
ˇEHAJIC
´-CLANCY
Intentions to respect IHL. Participants were told by their
respective interviewers, “I am now going to describe some things
that can happen in war. I would like you to imagine that you are
in each situation and tell me how you would behave if it were up
to you to make the decisions.” The situations participants were
asked to imagine referred to the pillars of IHL. For instance:
“Would you attack civilians who had helped the enemy by sup-
plying him with food or shelter of their own free will?” or “Would
you cut off supplies of food, water and medicines to civilians who
have fed or sheltered enemy combatants?” Participants indicated
their answer from 1 (No, never)to4(Yes, definitely; see the
Appendix under Intentions to Respect IHL) Scores were computed
by averaging participants’ answers to the six questions, and then
reversed, so that high scores meant strong intentions to respect IHL
(M!3.10; SD !.61; Cronbach’s alpha !.69).
Knowledge of IHL. Six items measured knowledge of IHL
(e.g., “Does IHL ban attacks on enemy combatants in a town or
village if it is known that many civilians will die as a result?”;
“Does IHL allow you to ill-treat or torture an enemy prisoner in
order to get important military information from him?). On each
item, participants scored 0 for the wrong answer and 1 for the
correct answer. A composite score was created by averaging
the six items (M!.79; SD !.25; Cronbach’s alpha !.69). (See
the Appendix under Knowledge of IHL for items.)
Results
The population of combatants interviewed for this study was
unfamiliar with the process of interviewing, and it was made clear
to them that they could stop at any time, or simply skip any
question they were asked. Thus, most variables had some missing
values, causing the statistics reported below to have different
degrees of freedom. Participants come from four different coun-
tries. Here we do not focus on country-specific patterns, but rather
on identifying relations between variables that held over and
beyond such specificities. Congruently, we report analyses without
country as a covariate, and we only report country effects for a
specific analysis if entering it as a covariate altered the pattern of
findings. Degrees of freedom can vary slightly because of missing
values on specific variables.
Accounting for Past Violent Violations of IHL
A first theoretically meaningful predictor is combatant status:
volunteer versus recruit. It was used as predictor in a generalized
linear model (GLM) with violent past violations as the dependent
variable. Combatant status was a significant predictor, F(1, 294) !
5.96, p#.01, $
2
!.02, such that volunteers reported engagement
in violent past violations to a greater extent than recruited com-
batants (M!.06 and M!.02, respectively). Adding country as
covariate, however, reduced the effect of combatant status, F(1,
289) !2.10, p#.14, $
2
!.02, although the adjusted means
indicated that the pattern remained the same (adj.M!.06 and
adj.M!.03, for volunteer and recruited combatants, respectively).
We will return to this point in the discussion. Analyses using the
dichotomous version of the variable past violent violations con-
firmed the main result, chi-square !4.45, p#.03. Among
volunteers, 27% reported having committed violence, while among
recruited only 11% did.
Second, we looked at the effect of violent victimization.
Violent victimization (dichotomous) marginally predicted vio-
lent past violations, F(1, 290) !3.54, p#.06, $
2
!.01. As
expected, those who had been victim of violence reported
greater violent past violations (M!.07) than those who re-
ported not being a victim (M!.04). When using the continuous
version of Violent Victimization, the results were similar, F(1,
290) !3.27, p#.07, %!.10.
We then tested whether the effect of violent victimization on
violent past violations was mediated by combatant status. It was
predicted that violent victimization would increase likelihood that
the respondent be a volunteer, which, in turn, is associated with
greater tendency to perpetrate violence as measured by violent past
violations. Mediation was assessed using MPlus bootstrapping for
dichotomous mediators (Muthén & Muthén, 1998–2012). We
found a significant indirect effect of violent victimization on
violent past violations via combatant status: b!.075, SE !.063,
95% CI [.015, .223], and a nonsignificant direct effect of violent
victimization on violent past violations: b!.155, SE !.121, 95%
CI [&.030, .369], suggesting that combatant status mediated the
relationship between violent victimization and violent past viola-
tions.
Intentions to Respect IHL
Three predictors of Intentions are theoretically meaningful:
combatant status (recruit vs. volunteer); violent past violations;
and knowledge of IHL—from now on referred to as “knowledge.”
As reported above, combatant status and violent past violations are
not independent: the former predicts the latter. However, there is
plenty of unexplained variance in violent past violations, after
accounting for the effect of combatant status, to justify including
them both as predictors. Furthermore, the two should be consid-
ered when investigating intentions to respect IHL because (a) past
behavior is a likely determinant of future behavior; and (b) anec-
dotal evidence reported by ICRC personnel suggests that status of
the combatant should affect intentions, over and beyond its effect
through violent past violations.
A GLM with intentions as dependent variable and the three
predictors with their interactions as independent variables revealed
the main effects of both knowledge and violent past violations, and
a two-way interaction between combatant status and violent past
violations. These were qualified by a three-way interaction, F(7,
288) !3.75, p#.05, $
2
!.01, and we thus interpret the
higher-order interaction. Separately, a two-way GLM were com-
puted for volunteer and recruited combatants. Among recruited
combatants, only knowledge was significant, F(3, 90) !5.90, p#
.01, $
2
!.06, indicating that the greater the knowledge, the greater
the intentions to respect IHL, %!.32. Among volunteers, both
main effects were significant and qualified by an interaction, F(3,
198) !5.56, p#.02, $
2
!.03. This indicated that knowledge had
a positive effect on intentions to respect IHL at both levels of
violent past violations, but this was weaker at high levels ('1SD)
of violent past violations, %!.16, p#.01, than at low levels (&1
SD) of violent past violations, %!.35, p#.001.
Violence and Self-Justification
Participants who reported committing violations of IHL were
further asked about their motivations for having done so, and their
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5
VIOLENCE, DEHUMANIZATION AND IHL AMONG COMBATANTS
answers resulted in scores on three justification categories: dis-
placement (of responsibility), demonization, and obedience.
Scores of these three variables were entered into a GLM model as
continuous, centered predictors using intentions as criterion, and
controlling for combatant status and knowledge—which, as re-
ported above, has an impact on intentions. Because only combat-
ants who reported having committed violations had justification
scores, the sample for this regression was smaller (N!88). In this
reduced sample combatant status was not a reliable predictor, but,
replicating the finding reported above using the whole sample,
knowledge was, F(5, 83) !8.15, p#.005, $
2
!.08. The greater
the knowledge, the greater the intentions to respect IHL, %!.28.
Among the justifications, displacement had a marginal effect, F(1,
83) !3.62, p#.06, $
2
!.04: The greater the displacement of
responsibility, the stronger the intentions to respect IHL, %!.20.
Demonization was also significant, F(1, 83) !11.16, p#.001,
$
2
!.12: The greater the demonization of the enemy, the lesser
the intentions to respect IHL in the future %!&.35.
2
Given the significant effect of demonization on intentions, and
the applied value of assessing the role of knowledge of IHL among
combatants, we assessed whether this effect was moderated by
knowledge. A GLM analysis was thus performed on intentions,
using demonization, knowledge (both centered) and their interac-
tion as independent variables. The interaction did not reach sig-
nificance, F(3, 90) !1.73, p#.19, $
2
!.02. We nonetheless
disentangled the nonsignificant interaction for exploratory pur-
poses. Knowledge at a marginal effect at low values of demoni-
zation (&1SD), t(90) !1.83, p#.07, %!.22 but a significant
effect at high values of demonization ('1SD), t(90) !3.30, p#
.001, %!.47. A look at means levels showed that while at low
levels of demonization high versus low knowledge individuals did
not differ much (M!3.39 vs. 3.12, respectively), at high levels of
demonization low knowledge individuals scored significantly
lower on intentions (M!2.53) compared to high knowledge
individuals (M!3.12). This pattern shows how knowledge of IHL
can buffer the effects of demonization of the enemy.
Discussion
In this study we investigated the role of social psychological
factors on the behavior of combatants. Specifically, we looked at
the interplay of victimization, combatant status (volunteer vs.
recruited), past violent violations of IHL, and intentions to respect
IHL in the future. The moderating role of knowledge of IHL and
justification strategies was also assessed.
A first research question focused on the role of previous expe-
rience as a victim of violence in the context of intergroup conflict
in predicting (reported) violent past behavior such as violations of
IHL (where violent violations refer to violence against human
beings, as opposed to property), as well as on the possible medi-
ational role of status of the combatant. Results showed that violent
experienced victimization is associated with greater likelihood of
being a volunteer (as opposed to recruited), and that this, in turn,
predicts greater violations of IHL (Bar-Tal & Hammack, 2012).
This result is consistent with the above-referenced research studies
appetite aggression, which show that such “appetite” is predicted
by the level of violence one has committed in the past and by
having experienced trauma (see also Weierstall & Elbert, 2011).
Appetite is related to our intentions variable; of the two predictors,
one is virtually identical to our measure of previously committed
violence and the second, trauma, is a correlate of our victimization
variable. Research on appetitive aggression has also specifically
found that volunteers display greater appetite for violence than
those who had been forced to join; a result that is very consistent
with the pattern of findings we observe in the current study
(Weierstall et al., 2013).
When interpreting the result concerning the impact of victim-
ization it is important to remember that our sample contained only
combatants. It is possible that a significant proportion of individ-
uals who are victims of violence withdrew from the conflict
altogether, and may have even migrated out of the country. As
noted earlier, the specific experience of violence can lead to a
variety of emotional responses, such as fear and anger. While
anger is thought of as an approach emotion, which leads to
engagement and confrontation, fear is conceived as an avoidance
emotion, related to withdrawal (Frijda, 1986; Mackie, Devos, &
Smith, 2000). Thus, as a result of the specifics characteristics of
the violence in conjunction with their own predispositions, some
victims might have experienced primarily the emotion of fear and
thus withdrawn from the conflict. Others victims whose emotional
response was primarily in terms of anger, on the contrary, might
have engaged in the conflict, for instance, by volunteering as
combatant—thus ending up in our sample. For this reason, we
should not conclude that victimization necessarily leads to engage-
ment with the conflict, but, rather, that among a sample of com-
batants having been the victims of violence in the past increases
the likelihood of a combatant being a volunteer, which, in turn,
impacts their behavior in violent conflict. As noted above, this
serves several psychological functions, including redressing a
sense of justice (Chernick, 2003) and fighting existential anxiety
through social identification (Castano & Dechesne, 2005); it also
provides mental health benefits (Kira et al., 2011).
A second question that was addressed focused on intentions to
respect IHL in the future. Here we tested the joint effects of three
factors: knowledge of IHL, status of the combatants, and the extent
of violent past violations. The pattern differed depending on the
status of the combatants. For recruited combatants, the picture was
fairly simple. Greater IHL knowledge leads to greater intentions to
respect it. Knowledge and clarity with regard to what is considered
acceptable and nonacceptable behavior in war is an important
predictor of behavior, as research on the effects of norms suggests
(e.g., Manstead, 2000). Among volunteers, violent past violations
of IHL also had an impact on intentions, but this effect was
moderated by knowledge. While knowledge mattered both among
those who reported low and those who reported high levels of past
violations of IHL, the effect of knowledge was weaker among the
latter. This suggests that while imparting knowledge is a key factor
in reducing violations of IHL, it is particularly important to do so
before combatants begin committing violations. This result is
consistent with the ICRC efforts to impart IHL knowledge to all
armed forces.
2
For these analyses too, we checked for the effect of country. Adding
country to the model did not alter the effect of knowledge or of demoni-
zation. The only difference was that the effect of deresponsabilization
vanished. However, it should be noted that four this analysis the Nwas
much reduced. Therefore the interpretation of the model with country as
covariate is problematic.
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6CASTANO, MUÑOZ-ROJAS, AND C
ˇEHAJIC
´-CLANCY
The role of past violations on the behavior of combatants,
described above, is likely due to inoculation effects (e.g., Brown-
ing, 1992; Martens, Kosloff, Greenberg, Landau, & Schmader,
2007; Staub, 1992). Violence begets violence, and once a person
has committed violence, norms against committing violence are
likely to weigh less than other factors (such as the need for
revenge) in their decision-making process. Furthermore, the mo-
rality systems which inform IHL, and specifically the “do not
harm” moral principle, may give way to other moral systems that
are less likely to support IHL-adherent behavior, such as “in-group
loyalty” or “respect for authority.” Building on the work on moral
foundations (e.g., Haidt, Graham, & Joseph, 2009), a series of
experiments showed that the relative salience of morality princi-
ples shifts depending on contextual factors (Leidner & Castano,
2012). In these experiments, it was the witnessing of ingroup-
perpetrated violence which undermined the salience of IHL-
consistent principles such as do not harm. Among combatants, it is
likely that being the perpetrator (or the target) of violence leads to
the same shift: the conflict becomes even more clearly about
hurting an enemy who has no morals and about obeying the
ingroup’s authorities, which thus ensures the welfare of the in-
group. The third set of findings emerging from our study sheds
further light on this process.
Among the self-justification processes that were investigated,
displacement of responsibility had a marginal effect on intentions
to respect IHL: the greater the displacement of responsibility for
past violent violations, the greater the intentions to respect IHL in
the future. This effect may seem paradoxical, but it is consistent
with the idea that if individuals can find an explanation for their
violent actions which does not involve denigrating the victims or
dehumanizing them (Castano & Giner-Sorolla, 2006), they do not
need to defend said actions, can acknowledge their inappropriate-
ness, and thus develop intentions not to engage in similar actions
in the future.
Demonization was negatively associated with intentions to re-
spect IHL in the future. Demonization corresponds to an essen-
tialistic negative interpretation of the outgroup’s behavior, which,
in this case, is violent behavior. It should be noted that the measure
did not simply tap into the perception of the enemy as evil; it was
about mentioning this reason (and correlated ones) to explain one’s
past violent behavior against the enemy. The demonization effect
on violence (Bar-Tal, 1990; Giner-Sorolla et al., 2012) is rein-
forced by the motivation to explain one’s behavior (Castano &
Giner-Sorolla, 2006). This finding points to the importance of
interventions aimed at modifying the image of the enemy held by
combatants in postconflict, transitional moments. Needless to say,
this is an extremely difficult outcome to achieve. In addition to
psychological needs (Castano, 2004b), this perception is influ-
enced by long-standing and deeply held beliefs about the other,
likely fostered by political discourse and propaganda prior to and
during conflict. Yet, de-demonization of the enemy emerges as an
important factor to reduce willingness of combatants to engage in
violent behavior in the future, and thus reduce intergroup conflict.
While the interaction between knowledge of IHL and demoni-
zation did not reach significance, we explored the impact of
knowledge at high and low levels of demonization, for it may offer
some indication for future research conducted with larger samples.
What we observed was that high knowledge brings levels of
intentions to respect IHL in the future among high demonizers to
the same level as low demonizers (see also Bar-Tal & Teichman,
2005). To the extent that knowledge of IHL acts as a teaching or
reminder of the universality of humanitarian law, this pattern is
consistent with recent findings by Leidner, Kardos, and Castano
(2018). These authors found that while pragmatic arguments
against torture (e.g., “Torturing prisoners is against the interests of
our own military”) do not have an impact on people’s attitudes
about torture and their support for it as a form of interrogation,
moral arguments (e.g., “Torturing prisoners is against the ideals of
the United States of America and its military”) reduced support for
torture, especially among the most hawkish participants.
We believe that the results reported above are of interest in as
much as they help shedding light on the complex web of social
psychological processes that are related to the violent behavior of
combatants. While interpreting these results, however, we should
keep in mind that they are based on self-report. As such, and given
the topic at hand, it is possible that social desirability concerns
might have impacted on participant’s responses. In order to min-
imize social desirability we took the four precautions detailed in
the Procedure section: including several reminders that responses
were confidential and had no bearings on ICRC action, and that
participation was voluntary and could be stopped at any time with
no prejudice; stressing the importance of truthfulness and sponta-
neity; and no remuneration. We did not include, in our survey,
specific social desirability scales. As it is typical in research using
combatants, in the studies on behavior of combatants and partic-
ularly on self-reporting of past violence that we have discussed
here, social desirability has not been directly measured. One ex-
ception is the study by Weierstall and Elbert (2011), which looked
at appetitive aggression amid a large sample of 1,632 former
combatants and participants in war-affected regions. In this study
the authors also used a shorter version of the Minnesota Multipha-
sic Personality Inventory Lie scale (Meehl & Hathaway, 1946), a
measure of social desirability. Their results showed no correlation
between social desirability tendencies and scores on the appetitive
aggression scale. Neither the precautions we took, nor previous
practice justifies or previous findings ensure, that the answers that
were given to our survey are completely truthful. Taken together,
however, the above offers some reassurance about the significance
of our findings.
It is also worth speculating about the possible effects of social
desirability on our dataset. One obvious effect would be the
underreporting of socially undesirable behavior. Another, more
pernicious effect, is that the underreporting could impact the
multivariate level of analyses. It is possible that those who re-
ported, say, lower levels of or no prior past violence, in fact
committed more or some of it, and it is possible that they are not
randomly distributed across all levels of the other variables, such
as having being the victim of violence and/or being a volunteer
versus a recruit. If so, we may be overestimating the relationship
between the variables that were investigated. Yet, it is not obvious
to expect that people who had lower incidence of victimization in
the past would be less willing to admit to having committed
violence against others, or more likely to say that they will respect
IHL in the future. If strong social desirability concerns were at play
they should be most evident in the questions about intentions to
respect IHL in the future—given that the participants were aware
that the interviewer was a representative of the ICRC and that
ICRC concerns itself with IHL. Yet, this variable presented a
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7
VIOLENCE, DEHUMANIZATION AND IHL AMONG COMBATANTS
rather normal distribution, with a kurtosis of &.57 and a skewness
of &.33, and not the highly skewed distribution one would expect
if the variable was heavily influenced by social desirability con-
cerns.
When conducting research on topics such as these, in addition to
be mindful about the motivation that respondents may have in
responding in specific ways, it is, of course, of paramount impor-
tance to think about the potential impact that the questions them-
selves may have on participants. ICRC is committed to protect
human beings, and, in fact, reducing harm (both physical and
psychological) is the very raison d(
être of the ICRC. Thus, in
addition to reviewing and approving the protocol, an effort was
made to ensure that the participants were not harmed in any way.
Participants were reminded unequivocally, after the survey was
introduced, that they were under no obligation to continue the
survey and could simply end their participation at that point. They
were also reminded, during the survey, that they were not obliged
in any way to answer each question, and, in fact, some skipped
some questions. Finally, the interviewers were delegates of the
ICRC, who have undergone extensive training in dealing with all
the correlates of violence and who also value immensely their
relation with the individuals belonging to the armed groups and
state armies they interact with during their stay in a given country,
which tends to last a few years. Perhaps because of all of this there
was no report of any participant feeling distressed by the inter-
viewing context. We cannot categorically exclude that some dis-
comfort might have been experienced by the participants in our
study, but we hope such distress will be outweighed by the benefits
that may stem from a better understanding of the social psycho-
logical underpinnings of violent conflict.
As noted earlier, our sample was comprised of combatants from
four countries (Bosnia-Herzegovina, The Republic of the Congo,
Georgia, and Columbia). Important differences exist between these
countries in terms history, language, culture, ethnic composition,
socioeconomic status, and, of course, the specific nature of the
conflict they experienced. Using country as a covariate turned out
to impact on only one of the major analyses reported here, namely,
the effect of combatant status on violent past violations (of IHL).
This result does not suggest that differences between countries can
be ignored when it comes to policy recommendation to prevent or
reduce conflict. It simply shows, consistent with the aim of the
present article, that some discernible, meaningful patterns emerge
that can help us build models of how social psychological factors
impact the behavior of combatants. Findings such as those pre-
sented here are useful because they tell us something about rela-
tions between fundamental social-psychological processes, but
when an applied goal is present they need to be understood in
concert with the social, political, cultural, economic, and historical
specificities of the context at hand. Future research with larger
samples is needed, so to be able to account for moderating factors
and provide more fine-grained analyses of how social psycholog-
ical factors impact on respect for IHL and, more broadly, on
intergroup violence.
Concluding Remarks
We reported findings from an empirical investigation of poten-
tial predictors of violent behavior in the context of intergroup
conflict. The data comes from an international sample of actual
combatants, reporting on their past and future behavior, as well as
on several social psychological factors related to such behavior
and intentions. As such, it is a unique sample, which is rarely
available in social psychological research, or in the social sciences
in general. While the contexts investigated were all characterized
by war, and thus violence was, in many instances, sanctioned, we
focused on violent behaviors that are not sanctioned, namely,
violations of IHL. Several important findings emerge.
First, being the actual victim of violence is a determinant of
one’s violent behavior, and that this is at least in part due to the fact
that victims (at least in the contexts that we investigated) are
particularly likely to become volunteer combatants. Second, inten-
tions to respect IHL in the future is affected by multiple factors:
the extent of past violent violations committed in the past, the
status of the combatant (volunteer vs. recruit), and the knowledge
of IHL. The pattern of findings points to the importance of the
work of the ICRC, alongside other institutions, in promulgating
knowledge of IHL. We do not know the exact mediating factors
through which this knowledge exerts its positive effect. The most
obvious one is that combatants are more likely to behave according
to IHL when they know exactly what it says. This is, of course, a
trivial, yet basic, factor. It could also be that coming into contact
with such a body of laws and norms changes the perspective that
combatants have on the enemy and the overall conflict and thus
their motivation to engage in “unnecessary” violent behavior. IHL
makes, directly and indirectly, the common humanity of the two
conflicting parties painfully salient. As suggested by social psy-
chological findings (for a review, see Castano, 2012) this human-
ization is likely to foster more positive behavior over and beyond
the important effect of norms.
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(Appendix follows)
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Appendix
Scales Used to Measure the Constructs of Interest
Victimization (Yes/No/Refuse to Reply). Utilized items are in
bold.
1. Have you been forced to leave your home?
2. Have you been taken prisoner?
3. Have you been held captive or taken hostage?
4. Have you been tortured?
5. Have you been deliberately humiliated?
6. Have you lost contact with any member of your family?
7. Has any member of your immediate family been killed
during the war? By “immediate family” I mean a son,
daughter, father, mother, brother, sister, grandmother,
grandfather, grandson, or granddaughter.
8. Have any of your possessions been seriously damaged?
9. Have you been injured during the fighting?
10. Have soldiers or other combatants taken your food?
11. Has your home been looted?
12. Has anyone you know well been sexually assaulted or
raped by soldiers or other combatants?
Violent Past Violations (Me/Somebody I know/Neither/Refuse to
respond). Utilized items are in bold.
Have you done any of the following while a combatant, or do
you know any other combatant on your side who has?
1. forced someone to leave his home
2. killed a captured enemy combatant
3. held someone captive or taken someone hostage
4. tortured a prisoner
5. publicly humiliated a civilian who had supported the
enemy
6. attacked a hospital or a member of the Red Cross
7. killed a civilian who had been supporting the enemy
8. forced children or very young people to go into combat
9. taken food that belonged to someone else
10. looted or destroyed a house
11. sexually assaulted someone
Justifications (Yes/No/Refuse to respond). Bold, italic, or normal
font refers to, respectively, displacement of responsibility, demoni-
zation, and obedience.
Do you remember why you did what you did?
1. I hated the enemy
2. I had lost control
3. I was under the influence of drugs or alcohol
4. I was afraid
5. I was obeying orders
6. I knew that the enemy was doing the same
7. I wanted revenge for what had been done to me
8. I did not know the rules of war
9. I was not the person in charge
10. I was dragged along by the rest of the group
11. I believed this was a way of overcoming evil
Intentions to Respect IHL (No, Never; Probably not; Probably;
Yes, definitely)
1. Would you attack civilians who had helped the enemy by
supplying him with food or shelter of their own free will?
2. Would you cut off supplies of food, water and medicines
to civilians who have fed or sheltered enemy combatants?
3. Would you attack a group of enemy who were hiding in a
village, even if your attack was going to kill a large
number of civilians?
4. If the enemy executed people from your side whom they
had captured, would you do the same to enemy prisoners?
5. Would you ill-treat a prisoner to obtain important military
information?
(Appendix continues)
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VIOLENCE, DEHUMANIZATION AND IHL AMONG COMBATANTS
6. Would you attack an ambulance marked with a red cross
if you knew it was carrying injured enemy combatants?
Knowledge of IHL (Yes, international humanitarian law allows
that; No, international humanitarian law does not allow that;
Refused/no reply)
1. Does IHL allow you to deprive civilians of food, water or
medicines if they openly support the enemy?
2. Does IHL ban attacks on enemy combatants in a town or
village if it is known that many civilians will die as a
result?
3. Does IHL law say that you must not kill a captured enemy
combatant even if the enemy are executing your comrades
when they are captured?
4. Does IHL allow you to ill-treat or torture an enemy prisoner
in order to get important military information from him?
5. Does IHL ban combatants from attacking an ambulance
marked with the Red Cross, even if the vehicle is carrying
injured enemy combatants?
6. Does IHL allow combatants to attack civilians who are
giving the enemy food and shelter of their own free will?
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