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Incentives and Constraints: A Configurational Account of European Involvement in the anti-Daesh Coalition

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In 2014, the United States initiated the formation of a multilateral military operation against Daesh in Syria and Iraq. Eventually, more than 70 states joined the anti-Daesh coalition. However, contributions to the military effort have been characterized by great variance, especially among EU member states. While some states took leading roles in the airstrikes, others provided training for Iraqi and Kurdish forces, and still others did not get involved beyond voicing their support for the policy. Against this backdrop, this article makes a twofold contribution to the literature on military coalitions and security policy. Empirically, the article provides a mapping of the then 28 EU member states’ military engagement in the fight against Daesh in Syria and Iraq. Analytically, fuzzy-set Qualitative Comparative Analysis (fsQCA) is applied to account for the observed pattern of military involvement, using an integrative framework that combines international and domestic factors. The results demonstrate that multiple paths led towards EU military involvement in the anti-Daesh coalition. At the same time, international-level incentives, such as external threat and/or alliance value feature prominently in all three identified paths. The analysis further underscores the value of a configurational perspective, because neither an external threat nor alliance value are sufficient on their own to bring about the outcome. Across the set-theoretic configurations, these conditions either combine with other “push” factors or with the absence of constraints against military involvement. In line with the latter, the article highlights the policy relevance of institutional constraints, especially legislative veto rights, since most of those countries that were involved in the airstrikes of the anti-Daesh coalition did not have formal parliamentary involvement on matters of military deployment policy.
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RESEARCH ARTICLE
Incentives and constraints: a configurational account of
European involvement in the anti-Daesh coalition
Patrick A. Mello*
Technical University of Munich, Hochschule für Politik München, München, Germany
*E-mail: mello@hfp.tum.de
(Received 18 February 2021; revised 16 November 2021; accepted 17 November 2021; first published online 24 February 2022)
Abstract
In 2014, the USA initiated the formation of a multilateral military operation against Daesh in Syria and Iraq.
Eventually, more than 70 states joined the anti-Daesh coalition. However, contributions to the military effort have
been characterized by great variance, especially among EU member states. While some states took leading roles in
the airstrikes, others provided training for Iraqi and Kurdish forces, and still others did not get involved beyond
voicing their support for the policy. Against this backdrop, this article makes a two-fold contribution to the litera-
ture on military coalitions and security policy. Empirically, the article provides a mapping of the then 28 EU
member statesmilitary engagement in the fight against Daesh in Syria and Iraq. Analytically, fuzzy-set
Qualitative Comparative Analysis (fsQCA) is applied to account for the observed pattern of military involvement,
using an integrative framework that combines international and domestic factors. The results demonstrate that
multiple paths led towards EU military involvement in the anti-Daesh coalition. At the same time, international-
level incentives, such as external threat and/or alliance value feature prominently in all three identified paths. The
analysis further underscores the value of a configurational perspective, because neither an external threat nor alli-
ance value are sufficient on their own to bring about the outcome. Across the set-theoretic configurations, these
conditions either combine with other pushfactors or with the absence of constraints against military involvement.
In line with the latter, the article highlights the policy relevance of institutional constraints, especially legislative
veto rights, since most of those countries that were involved in the airstrikes of the anti-Daesh coalition did not
have formal parliamentary involvement on matters of military deployment policy.
Keywords: coalition warfare; foreign fighters; Islamic State; legislative constraints; security policy
Introduction
In September 2014 President Obama announced the formation of a multilateral coalition to roll
backthe terrorist threat emanating from the so-called Islamic Statein Iraq and Syria (WH,
2014).1Three months later, representatives from across the globe met in Brussels and passed
a joint statement that outlined goals in the global fight against Daesh, including the support
of military operations, capacity building, and training, as well as addressing the unfolding
humanitarian crisis in the region (DoS, 2014). On November 17, 2015, in the wake of a series
of terrorist attacks in Paris, including the bombing at the Bataclan concert hall, and the earlier
attacks against the satirical newspaper Charlie Hebdo, France invoked Article 42 (7) of the
© The Author(s), 2022. Published by Cambridge University Press on behalf of European Consortium for Political Research. This is an Open
Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which
permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
1The group is variously referred to as IS (Islamic State), ISIS (Islamic State in Iraq and al-Sham), ISIL (Islamic State in Iraq
and the Levant), or Daesh (al-Dawla al-Islamiya fil Iraq wa al-Sham). The US government mostly uses the term ISIL,
whereas France and the UK have made it their policy to call the group Daeshbecause that term carries negative connotations
in Arabic and it does not legitimize the group as an Islamic state(Connable et al., 2017).
European Political Science Review (2022), 14, 226244
doi:10.1017/S1755773921000333
https://doi.org/10.1017/S1755773921000333 Published online by Cambridge University Press
European Unions Lisbon Treaty, calling upon European solidarity and assistance in the fight
against Daesh (EP, 2015). Three days later, the UN Security Council passed Resolution 2249,
condemning Daesh for its continued gross systematic and widespread attacks directed against
civiliansand calling upon member states to take all necessary measures in compliance with inter-
national law.
Since 2014, more than 70 states and five international organizations have officially joined the
multidimensional fight against Daesh.2In March 2019, the last Daesh-held territory in Syria was
re-captured by coalition-backed forces. However, contributions to the US-led military coalition
have been characterized by great variance, especially among EU member states. While some states
took leading roles in the airstrikes against Daesh, others provided training for local forces, often
within the Kurdish Training and Coordination Center (KTCC) in Erbil, and still others did not get
involved beyond expressing their political support for the policy. How to explain this variation
among EU member statescontributions to the anti-Daesh coalition? Several studies have docu-
mented the early phases of the US-led coalition and explored potential explanations for the
observed variance in deployment policies across countries (McInnis, 2016; Saideman, 2016;
Haesebrouck, 2018), whereas others have focused on individual countriescontributions
(Doeser and Eidenfalk, 2019; Massie, 2019; Pedersen and Reykers, 2020), but there has not been
a systematic comparison of EU member state involvement in the fight against Daesh.3Since the
2015 incident was the first invocation of the Lisbon Treatys mutual defense clause, it is of partic-
ular policy relevance to conduct such a comparison across EU members and their foreign and
security policies. Focusing on the nexus between international and domestic politics, this paper
also speaks to the dynamics of multilateral military coalitions that have become pervasive in inter-
national security, as nearly all contemporary conflicts occur in the context of alliances, coalitions,
or international organization auspices (Kreps, 2011; von Hlatky, 2013; Auerswald and Saideman,
2014; Weitsman, 2014; Mello and Saideman, 2019; Schmitt, 2019).
Against this backdrop, the article makes a two-fold contribution to the literature on security
policy and participation in military coalitions. Empirically, it provides a mapping of the then 28
EU member statesmilitary engagement in the fight against Daesh in Syria and Iraq, whose contri-
butions ranged from combat involvement in the air strikes, air support functions, the provision of
training to local forces, to mere political and/or logistical support for the coalition. Analytically,
fuzzy-set Qualitative Comparative Analysis (QCA) is applied to develop a configurational account
for the observed pattern of EU involvement in the anti-Daesh coalition, based on an integrative
theoretical framework that combines international- and domestic-level factors, which are concep-
tualized as incentives and constraints for decisions on military involvement. The conditions
include the number of citizens who joined Daesh as foreign fighters (as an indicator for an external
threat), the value placed on a countrys alliance relationship, the political left-right position of its
government, the presence of parliamentary veto rights over military deployments, and a measure
of the extent to which the public perceives terrorism and foreign fighters as a security challenge.
As a set-theoretic comparative method, QCA is ideally suited to account for complex causation,
indicated by the presence of multiple paths (equifinality) and combinations of conditions
(conjunctural causation) leading to an outcome. This makes it a suitable methodological choice
for this study because none of the explanatory conditions are expected to be individually necessary
and/or sufficient. To the contrary, theory and prior work suggest combinations of conditions and
alternative paths towards the outcome.
2Among other organizations, the fight against Daesh has been supported by the European Union, Arab League, NATO,
INTERPOL, and the Community of Sahel-Saharan States.
3The studies by Saideman (2016) and Haesebrouck (2018) were limited to the initial phase of the anti-Daesh coalition,
without taking into account later contributions, such as the military involvement of Germany, Italy, and Poland, among
others. Importantly, these studies also did not consider public opinion as an explanatory factor. Moreover, this contribution
draws on newly available sources documenting the presence of foreign fighters in Syria and Iraq, which were not available as
prior studies appeared (e.g., TSC, 2017; UNODC, 2019).
European involvement in the anti-Daesh coalition 227
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Indeed, the results demonstrate that multiple paths led towards EU military involvement in the
anti-Daesh coalition. At the same time, international-level incentives, such as external threat
and/or alliance value feature prominently in all three identified paths. Moreover, the analysis
underscores the value of a configurational perspective because neither external threat nor alliance
value are sufficient on their own to bring about the outcome. Across the configurations entailed in
the set-theoretic solution, these either combine with other pushfactors or with the absence of
constraints against military involvement. In line with the latter, the paper highlights the policy
relevance of institutional constraints, especially legislative veto rights, since most of those
countries that were involved in the airstrikes of the anti-Daesh coalition did not have formal
parliamentary involvement on matters of military deployment policy (Ruys et al., 2019).
This suggests that legislative veto rights can, under certain preconditions, constrain the war
involvement of democracies, which resonates with prior studiesfindings (Dieterich et al.,
2015; Wagner, 2018) and underlines the political importance of this institutional constraint.
The article proceeds in four steps. The next section develops the integrative theoretical frame-
work to account for EU contributions to the anti-Daesh coalition. This is followed by an intro-
duction to the articles method and data. The ensuing section contains the set-theoretic analysis of
EU countriesmilitary contributions and a discussion of the analytical results. The article
concludes by summarizing its findings, outlining the relevance for studies on security policy
and coalition warfare, describing inherent limitations of the present study, and suggesting direc-
tions for future research.
Accounting for military contributions to the anti-Daesh coalition
Why do states decide to join military coalitions? Prior studies alternately emphasize the impor-
tance of alliance membership (Snyder, 1997), threat perception (Walt, 1987), international hier-
archy (Lake, 2009), alliance value (Davidson, 2014), or diplomatic embeddedness (Henke, 2017)
as reasons why states decide to join military coalitions. Apart from these general explanations, for
the anti-Daesh coalition it might have also mattered that many countries did not want to repeat
their experiences from the long-lasting campaigns in Afghanistan and Iraq (Saideman, 2016;
Schmitt, 2019). Moreover, domestic institutions and politics may have played important roles
in the decision-making processes on whether or not to participate militarily in the coalition
(Milner and Tingley, 2015). Decisions on military contributions are usually decided at the cabinet
level, which means they are subject to party politics (Wagner et al.,2017). Governments further
operate under institutional and legal constraints, such as parliamentary veto rights over military
deployments (Peters and Wagner, 2011; Ruys et al.,2019) and they usually observe public opinion,
which can form an additional constraint against military involvement (Baum and Potter, 2015;
Everts and Isernia, 2015). Building on previous efforts to combine such international and
domestic-level explanations (e.g., Bennett et al., 1997; Haesebrouck, 2018; Massie, 2019; Mello,
2019), this article develops an integrative theoretical framework to explain EU member states
military contributions to the anti-Daesh coalition in Iraq and Syria, as outlined in the following
sections.4
External threat
From a realist perspective, a primary driver of why states join a military coalition or increase their
allied cooperation is that they feel threatened (Walt, 1987). The swift rise of Daesh combined with
an apparent increase in terrorist activity in Europe and elsewhere certainly increased leaders
4The focus on five international and domestic-level factors should not be taken to rule out the existence of other potentially
relevant factors that could not be considered in this study. However, the analytical results show that the integrated framework
provides for consistent and comprehensive paths towards military involvement in the anti-Daesh coalition.
228 Patrick A. Mello
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willingness to do somethingabout this new phenomenon (Gerges, 2016), especially after the
occurrences in Paris in January 2015, when terrorists killed 12 people in their attack on the satir-
ical newspaper Charlie Hebdo, and during the series of terrorist attacks in November 2015,
including the bombing at the Bataclan concert hall where 130 people were murdered, after which
France subsequently invoked Article 42 (7) of the European Unions Lisbon Treaty, calling upon
European solidarity in the fight against Daesh. This was compounded by reports about a steady
flow of foreign fighters arriving in Syria and Iraq to join Daesh (UNODC, 2019). While estimates
vary, most reports came to the conclusion that a substantial share of the 30,000 foreign fighters
who joined Daesh originated from Western Europe, including large numbers from France,
Germany, and the UK, and smaller numbers from Belgium, Denmark, the Netherlands and
Sweden (Dodwell et al.,2016; TSC, 2017).5Since some of these foreign fighters have committed
extreme acts of violence in Daesh-held territory, and others have engaged in terrorist activities in
third countries, their eventual return to their countries of origin was seen as a grave security threat
in many European states. Hence, the external threat perspective suggests that countries with
foreign fighters in Syria and Iraq had a particular incentive to join the anti-Daesh effort.
Alliance value
Another explanation for military involvement in coalition operations pertains to the value that
states place on their alliance relationship (Davidson, 2014; Massie, 2019). This is related, but
not identical to long-standing arguments about alliance dependence (Bennett et al., 1997;
Snyder, 1997). Accordingly, states may value a security alliance and their relationship with an
alliance leader for different reasons. These may be related to their security needs, but the reasons
can also derive from status seeking (Pedersen and Reykers, 2020), concerns about reputation
(Oma and Petersson, 2019), or economic incentives (Newnham, 2008; Henke, 2019). For example,
Eastern European countries particularly the Baltic states and Poland value NATO membership
and their close relations with the USA because this serves as a credible security guarantee against
the threat posed by neighboring Russia (Doeser and Eidenfalk, 2019). Others, such as Denmark,
the Netherlands, or the UK, traditionally regard a close relationship with the USA as a way to
maintain international influence and standing (Ringsmose, 2010).6Applying such arguments
to NATO, Ringsmose (2010, 331) distinguishes between Article 5ersand Atlanticists.
The former are states that feel insecure or threatened and thus emphasize NATOs mutual defense
clause. The latter are countries that traditionally maintain special relationshipswith the USA.
Both of these groups would be expected to support and contribute to US-led military operations,
like the anti-Daesh coalition, even when such a mission is conducted outside the official organi-
zational framework of NATO.
Parliamentary veto rights
Recent institutionalist work has explored the role of parliaments in security policy and investi-
gated the effects of specific forms of institutional constraints, such as constitutional restrictions
and parliamentary veto rights on the security policies of consolidated democracies (Peters and
Wagner, 2011; Dieterich et al.,2015). This literature emphasizes that decisions about military
deployments are often dependent upon structural and procedural restrictions, and that parlia-
ments are important actors also in security policy, particularly, but not exclusively, when legis-
latures hold a formal veto right over military missions (Kesgin and Kaarbo, 2010; Oktay, 2018;
Coticchia and Moro, 2020). While mandatory parliamentary involvement can also yield
5On the economic drivers of Daeshs recruitment of foreign fighters, see Brockmeyer et al. (2018). The role of women in
Daesh is analyzed in Loken and Zelenz (2017).
6For an illustration of alliance value considerations in Canada, see von Hlatky and Massie (2019).
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unintended consequences (Lagassé and Mello, 2018), the general expectation is that whenever
legislatures have a say on military missions this creates an additional hurdle for government
engagement. To be sure, this is not an absolute constraint. But when there is substantial public
opposition, then military contributions are not expected to be approved by parliament.7
Moreover, due to a fusion between government and opposition in parliamentary democracies,
such preferences against military engagement will often be anticipated by governments. This
means that, more often than not, governments will refrain from submitting a motion on a military
deployment if they have reason to fear a parliamentary veto on the issue.8
Party politics
The realist conjecture that politics stops at the waters edgehas long dominated IR thinking about
partisanship and security policy (Gowa, 1998; Milner and Tingley, 2015). Yet an emerging literature
shows that ideological differences between parties on the left and the right also affect the way that
parties formulate foreign and security policies and how they implement these once in government
(Rathbun, 2004; Hofmann, 2013;Wagneret al., 2017; Coticchia and Vignoli, 2020; Wenzelburger
and Böller, 2020). For instance, Wagner et al. (2017) demonstrate that while right-of-center parties
are generally more supportive of military missions, theres a curvilinear relationship with decreasing
support towards both ends of the political spectrum. Yet, when examining actual involvement in
military operations, Haesebrouck and Mello (2020) find that left-wing governments were more
inclined to participate(2020, 581). Given this mixed evidence, it is difficult to derive clear-cut
expectations on partisanship for the anti-Daesh coalition. On the one hand, coalition activities
are multi-faceted and range from airstrikes to training of local forces and humanitarian aid.
On the other hand, the military effort is decidedly robust, and it takes place outside the organiza-
tional frameworks of NATO or the EU. On this basis, right-of-center governments may be expected
to be more supportive of actually deploying forces than their left-leaning counterparts.
Public opinion
Public opinion is a central building block in many theories of the democratic peace and demo-
cratic conflict behavior more generally (Doyle, 1983; Everts and Isernia, 2015; Ozkececi-Taner,
2017). The reasoning behind the idea of a public constraintgoes back to Kants famous proposi-
tion that citizens would decide against war if they had a say in the decision, assuming that they
would have to bear the brunt of the burden of warfighting (Kant, 2007, 100). Yet, when applied to
a contemporary context, we may call into question whether the public truly constitutes a
constraint on government behavior because the population is unequally affected by the human
and material costs of war (Kriner and Shen, 2010). However, as studies have shown, given that
certain preconditions are met, public opinion can stop governments from unpopular military
engagements. For instance, Dieterich et al. (2015) show that war-averse publics, combined with
institutional constraints, stopped many European governments from becoming engaged in the
Iraq War. More generally, Baum and Potter (2015) argue that public opinion and media access
are key variables to understand democratic constraint in foreign policy. From this perspective,
public support, or a lack thereof, can be seen as a key element to account for decisions on military
engagements. As developed below, this papers empirical focus rests on public threat perception,
understood as the extent to which citizens regard terrorism and foreign fighters as an important
security challenge for the European Union.
7A prime example is the Iraq War of 2003, where parliamentary veto rights and public opposition nearly always served as a
constraint on war involvement (Dieterich et al.,2015).
8The most prominent case of a parliamentary veto occurred in August 2013, when the British House of Commons voted
against Prime Minister Camerons proposal to engage in Syria (Kaarbo and Kenealy 2017; Strong, 2018).
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An integrated model of coalition contributions
Given the inherent multi-dimensionality of foreign policy decision-making, it seems appropriate
to expect complex interactions between the various relevant factors outlined in the previous
section. Against this backdrop, it is important to underline that none of the five aforementioned
factors is expected to independently account for the observed variance in military contributions to
the anti-Daesh coalition. Instead, I expect these conditions to form combinations of conditions
that either push towards military contribution or constrain a military engagement. The first two
factors, external threat and alliance value are both expected to be push factors that motivate
governments to join the anti-Daesh coalition. To the contrary, parliamentary veto rights and a
lack of public threat perception are considered to be constraints on government assertiveness.
Their combination is expected to be sufficient for the absence of military participation
(non-outcome). As mentioned above, party politics can cut both ways (Rathbun, 2004).
Yet, the general expectation would be that right-of-center governments are more willing to
contribute militarily than their left-leaning counterparts (Wagner et al.,2017), especially for
military operations that are aimed at fighting terrorism, such as the anti-Daesh coalition, even
though recent work suggests that left governments might be more inclined to become involved
militarily (Haesebrouck and Mello, 2020). From a methodological angle, each individual factor is
regarded as an INUS condition, which is an insufficient but necessary part of a condition, which is
itself unnecessary but sufficient for the result(Mackie, 1965, 245). INUS conditions essentially
encapsulate the idea of causal complexity that is central to Qualitative Comparative Analysis
and their conceptualization has informed numerous QCA applications (see, for instance, Ide,
2018). The method of QCA is introduced in the next section.
Method
This paper uses fuzzy-set Qualitative Comparative Analysis (QCA; Ragin, 2008) to investigate the
expected complex interaction between explanatory factors. As a set-theoretic method, QCA aims
at identifying necessary and sufficient conditions for an outcome. QCA is ideally suited to recog-
nize the combination of more than one factor (conjunctural causation) and the existence of
multiple pathways toward an outcome (equifinality). While QCA is widely used in many areas
of the social sciences (Rihoux et al., 2013), it can still be considered a novel approach in interna-
tional relations, and conflict research in particular. That being said, recent years have seen a
number of QCA applications in these fields, including on topics such as sanctions against authori-
tarian regimes (Grauvogel and von Soest, 2014), peace agreements (Caspersen, 2019), interna-
tional arms control treaties (Böller, 2021), post-conflict gender equality (Bhattacharya and
Burns, 2019), coalition defection in multilateral military operations (Mello, 2020), or the effective-
ness of international peacebuilding (Mross et al., 2021).
In contrast to the crisp-set variant of QCA, which works with binary values, fuzzy-set QCA
allows researchers to take into account qualitative and quantitative differences (Ragin, 2008).
Fuzzy sets can assume any value between 0 and 1. Using a software-based procedure,9quantitative
datasets can be calibrated into fuzzy sets by assigning three empirical anchors, which are
determined by the researcher.10 These three thresholds designate which scores in the data are
considered fully ina specified fuzzy set (resulting in a fuzzy value of 1), which scores are regarded
as neither in nor out(these receive a fuzzy value of 0.5), and which scores are fully outof the
respective set specified (receiving a fuzzy value of 0). The direct method of calibrationapplies a
9The analysis in this paper was conducted within the R software environment, using the packages QCA(Duşa, 2019) and
SetMethods(Oana and Schneider, 2018).
10For qualitative data, fuzzy scores are typically assigned manually, based on previously developed coding rules. The
calibration of the outcome uses this qualitative assignment approach to constructing fuzzy sets. See Table 1 and Table A1
in the online appendix.
European involvement in the anti-Daesh coalition 231
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logistic function that transforms the raw data into fuzzy values, based on anchors set by the
researcher (Ragin, 2008). This procedure returns fine-grained fuzzy values that show whether
a case is qualitatively rather inside or outside a set and to what quantitative extent the case shows
membership in a given fuzzy set.
Recent work emphasizes that crisp sets and fuzzy sets can, occasionally, yield different results
(Rohlfing, 2020, 86). As a robustness test, I complemented the fuzzy-set analysis with a crisp-set
alternative. Table A5 (online appendix) shows that the results are substantively identical, while
crisp sets lead to perfect consistency, PRI, and coverage scores. This means that the results are
robust, irrespective of which type of set is chosen. In line with good practices of calibration
(Skaaning, 2011;Duşa, 2019; Mello, 2021; Oana et al., 2021), I also report the calibration ranges
within which the results of the set-theoretic analysis do not change. The SetMethods package for
R provides a function to conduct such a test (Oana and Schneider, 2018; Oana et al., 2021), the
results of which are reported in Table A1. Other robustness tests concern the coding of the
outcome and a restricted model of conditions (see Tables A6 and A7 in the appendix). The first
test confirms that the results are not sensitive to a different assignment of scores, such as when
lower-level military involvement is assigned more weight in the calibration, whereas the second
effectively yields Path 2 of the reported intermediate solution (Table 1).
Military participation in the anti-Daesh coalition
The outcome to be explained is the military participation of the EU 28 in the anti-Daesh coali-
tion, also known as operation Inherent Resolve. The multilateral coalition was formed under
President Obama in September 2014 (WH, 2014),11 after a request from the Iraqi government.
Military operations against Daesh were initially limited to Iraqi territory and subsequently
expanded to Syria (in 201516). Combat intensity reached peaks in the summer of 2017,
when the UK-based NGO Airwars.orgreported civilian deaths due to airstrikes by the
Table 1. Solution paths for military participation in the anti-Daesh coalition
Paths
1234
External threat ••
Alliance value ••
Right executive
Parliamentary veto rights ⦻⦻
Public support ⦻⦻
Consistency 0.99 0.90 0.82 1.00
PRI 0.99 0.88 0.78 1.00
Raw coverage 0.53 0.31 0.31 0.33
Unique coverage 0.16 0.09 0.11 0.13
Covered cases/uniquely covered cases (bold) BEL DEU GBR DNK
FRA GBR ITA FRA
GBR ITA POL
ITA
NLD
Solution consistency 0.90
Solution PRI 0.88
Solution coverage 0.87
Model/total M2/2
Note: Black circles indicate the presence of a condition, crossed-out circles its absence. The solution entails two logically equivalent models.
Model 2 was chosen for the substantive interpretation due to its higher solution consistency and coverage. For a comparison, see Table A3.
11The official coalition website provides general information and details on individual countriescontributions: https://
theglobalcoalition.org (accessed November 16, 2021).
232 Patrick A. Mello
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US-led coalition of up to 2,600 in Iraq and 1,300 in Syria.12 Table 2summarizes military
contributions across the EU28 (including the UK before Brexit).13
Essentially, there are three groups of countries. The first group includes those that were actively
involved in the airstrikes, either by bombing targets themselves (UK, France, Belgium, Denmark,
and the Netherlands) or through the provision of air support or reconnaissance operations
(Germany, Italy, and Poland). Notably, contributions in this category were made at different
points in time. Whereas the UK and France conducted airstrikes from September 2014 onward,
Belgium, Denmark, and the Netherlands followed a month later. Italy deployed reconnaissance
aircraft in November 2014, while Germany followed in similar functions in December 2015, and
Poland in June 2016. The second group of countries contains those who limited their contribution
to training local forces, mostly at the Kurdish Training Coordination Center (KTCC) in Erbil, but
also in other locations. While all of these were small-scale training missions, some countries
deployed substantial numbers (between 30 and 500 soldiers, including Spain, Hungary,
Finland, Sweden, Romania, and Portugal), whereas others send only a handful of officers for
the instruction of local forces (the Baltic countries and Slovenia). Finally, a third group of coun-
tries made no material contributions beyond logistics (overflight and basing rights in Greece and
Table 2. Military contributions to the anti-Daesh coalition
Country
Fuzzy
value Military Contribution to the anti-Daesh coalition Since Personnel
UK 1.0 Air strikes in Iraq and Syria, training local forces 09/2014 1350
France 1.0 Air strikes in Iraq and Syria, training local forces 09/2014 1000
Netherlands 1.0 Air strikes in Iraq and Syria, training local forces 10/2014 150
Belgium 1.0 Air strikes in Iraq and Syria, training local forces 10/2014 150
Denmark 1.0 Air strikes in Iraq and Syria, training local forces 10/2014 140
Italy 0.8 Air support, training local forces 11/2014 1500
Germany 0.8 Air support, training local forces 12/2015 1200
Poland 0.8 Air support 06/2016 150
Spain 0.2 Training local forces 01/2015 480
Hungary 0.2 Training local forces 01/2015 116
Finland 0.2 Training local forces 01/2015 100
Sweden 0.2 Training local forces 08/2015 70
Romania 0.2 Training local forces 01/2016 50
Portugal 0.2 Training local forces 01/2015 30
Latvia 0.1 Training local forces 11/2015 6
Estonia 0.1 Training local forces 08/2016 6
Slovenia 0.1 Training local forces 09/2016 6
Lithuania 0.1 Training local forces 01/2017 6
Czech Republic 0.1 Training local forces 08/2017 4
Cyprus 0.0 Political and logistical support (overflight and basing) ––
Greece 0.0 Political and logistical support (overflight and basing) ––
Austria 0.0 Political support ––
Bulgaria 0.0 Political support ––
Croatia 0.0 Political support ––
Luxembourg 0.0 Political support ––
Slovakia 0.0 Political support ––
Ireland 0.0 No involvement ––
Malta 0.0 No involvement ––
Sources: Own compilation based on Drennan (2014), McInnis (2016), Saideman (2016), informa tion from ministries of defense, and the
coalition website: http://theglobalcoalition.org (accessed October 8, 2020).
12These are estimates based on varying quality of reporting. For the observed timeframe, casualty data on Syria reached a
higher level of confidence (e.g., confirmation by several sources or accepted responsibility by a belligerent). Detailed assess-
ments are available at: https://airwars.org/conflict/coalition-in-iraq-and-syria/ (accessed November 16, 2021).
13The table draws on Drennan (2014), McInnis (2016), and Saideman (2016), updated with information from countries
ministries of defense and the coalition website (see above). Emphasis is placed on countriescore military contribution, not
taking into account other forms of regional involvement, such as humanitarian aid.
European involvement in the anti-Daesh coalition 233
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Cyprus) or expressions of political support (Austria, Bulgaria, Croatia, Luxembourg, and
Slovakia). Two countries did not officially endorse the anti-Daesh coalition (Ireland and Malta).
Fuzzy values reflect the primary criterion of whether countries were involved in the airstrikes,
with slightly lower values assigned to those who restricted their contribution to air support. While
training contributions often also entailed substantial military personnel, these were assigned lower
scores due to the different qualitative nature of the involvement. From the perspective of demo-
cratic politics, key questions concern the risks associated with a military deployment and the
legality and legitimacy of the mandate. Hence, the fuzzy values reflect the major difference
between contributing to the airstrikes (which often requires parliamentary approval) and other
kinds of contributions, which are often outside the scope of parliamentary veto rights and receive
substantially less attention in parliament and among the public.14
Explanatory conditions: data and calibration
The set-theoretic analysis contains five explanatory conditions: external threat (T), alliance value
(A), right executive (R), parliamentary veto rights (V), and public threat perception (P). Table 3
lists the EU 28 by relevant cabinet or government leader and provides raw data and calibrated
fuzzy values for the included conditions. This section summarizes the fuzzy-set calibration of the
included conditions and outcome, which is the transformation of qualitative and/or quantitative
raw data into set-theoretic membership scores used for QCA (Ragin, 2008; Schneider and
Wagemann, 2012; Mello, 2021). Additional documentation is given in the online appendix.
External Threat indicates whether citizens of the respective state have gone to Syria or Iraq to
join Daesh as foreign fighters. Data on foreign fighters stems from the Soufan Center and Global
Strategy Network (TSC, 2017). Given the nature of the phenomenon, the numbers cited remain
estimates, albeit most of these have been confirmed in later investigations (see also UNODC,
2019). For September 2015, a total of 30,000 foreign fighters from over 100 countries were esti-
mated to be in Syria. About 5,000 of these came from EU countries. The empirical pattern is rela-
tively clear-cut: 12 EU states had citizens who joined Daesh as foreign fighters, many of these
countries also experienced deaths from jihadi-motivated terrorist attacks on their own soil.15
The fuzzy-set condition external threat was calibrated so that all countries with foreign fighters
receive fuzzy-set values above 0.50, whereas those without received a value of 0. Countries with
200 or more foreign fighters were considered fully insidethe set external threat.
Alliance Value reflects whether a country has specific incentives to contribute militarily, rooted
in its alliance relationship. The measure rests on an aggregate index that takes into account:
(1) whether the country has a formal alliance membership in NATO; (2) is considered dependent
on the alliance for its security; and (3) whether it is generally regarded as following an Atlanticist
foreign policy orientation. The first indicator simply distinguishes between NATO and non-
NATO members. The second indicator, alliance dependence reflects the security concerns of
countries like the Baltic states Estonia, Latvia and Lithuania as well as Poland. Due to their
conflictive neighborhood with Russia, these four EU members have the greatest interest in
securing a strong partnership with the USA and therefore seek to maintain a status as loyal
NATO members. Finally, the third indicator takes into account countries with a strong
Atlanticist foreign policy orientation such as the UK, Denmark, and the Netherlands, as apparent
from the UKs traditional special relationshipwith the USA or the Danish opt-outfrom the EUs
Common Foreign and Security Policy (CFSP). My estimate of Atlanticist foreign policy
14See also the robustness test reported in Table A6.
15There is empirical overlap between countries that experienced jihadi-motivated terrorist attacks on their own soil and
those with foreign fighters in Iraq and Syria. However, while six countries recorded deadly terrorist attacks during the
observed timeframe (GTD, 2018), 12 of the EU-28 had citizens as foreign fighters among Daesh (TSC, 2017). Hence rather
than analyzing these factors separately, this study focuses on foreign fighters.
234 Patrick A. Mello
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Table 3. EU governments and explanatory conditions
Country
Cabinet/govern-
ment leader
External threat Alliance value Right executive
Parl.
veto Public support
Fuzzy
values
Foreign
fighters
Fuzzy
values
Alliance
index
NATO
member
Atlant.
orient.
Alliance
depend.
Fuzzy
values
Left-right
(CHES)
Crisp
values
Fuzzy
values
Public
opinion
Austria Faymann II 0.99 296 0.00 0 0 0 0 0.52 5.03 1 0.00 70%
Belgium Di Rupo II 1.00 478 0.19 1 1 0 0 0.57 5.09 0 0.98 91%
Bulgaria Borisov II 0.53 10 0.19 1 1 0 0 1.00 7.02 1 0.73 88%
Croatia Milanovic 0.00 0 0.19 1 1 0 0 0.00 2.97 1 0.03 79%
Cyprus Anastasiades II 0.00 0 0.00 0 0 0 0 1.00 8.45 1 0.95 90%
Czech Republic Sobotka 0.00 0 0.19 1 1 0 0 0.25 4.62 1 0.73 88%
Denmark Thorning-Schmidt II 0.89 145 0.95 2 1 1 0 0.07 4.11 1 0.95 90%
Estonia Roivas I 0.00 0 0.95 2 1 0 1 0.99 6.55 1 0.30 85%
Finland Stubb I 0.76 80 0.00 0 0 0 0 0.79 5.45 1 0.99 92%
France Hollande 1.00 1910 0.19 1 1 0 0 0.00 3.20 0 0.98 91%
Germany Merkel III 1.00 915 0.95 2 1 1 0 0.69 5.27 1 0.11 82%
Greece Samaras II 0.00 0 0.19 1 1 0 0 0.98 6.25 0 0.40 86%
Hungary Orban III 0.00 0 0.19 1 1 0 0 0.99 6.61 1 0.40 86%
Ireland Kenny I 0.00 0 0.00 0 0 0 0 0.80 5.48 1 0.01 77%
Italy Renzi 0.83 110 0.95 2 1 1 0 0.01 3.40 0 0.07 81%
Latvia Straujuma 0.00 0 0.95 2 1 0 1 1.00 7.17 1 0.22 84%
Lithuania Butkevicius 0.00 0 0.95 2 1 0 1 0.03 3.79 1 0.95 90%
Luxembourg Bettel I 0.00 0 0.19 1 1 0 0 0.18 4.49 1 1.00 94%
Malta Muscat I 0.00 0 0.00 0 0 0 0 0.09 4.20 1 0.99 92%
Netherlands Rutte III 0.98 280 0.95 2 1 1 0 0.82 5.52 0 0.95 90%
Poland Tusk II 0.00 0 1.00 3 1 1 1 0.94 5.96 0 0.16 83%
Portugal Passos Coelho I 0.00 0 0.95 2 1 1 0 0.99 6.61 0 0.88 89%
Romania Ponta III 0.00 0 0.95 2 1 1 0 0.01 3.57 1 0.88 89%
Slovakia Fico II 0.00 0 0.19 1 1 0 0 0.01 3.40 0 0.11 82%
Slovenia Cerar 0.00 0 0.19 1 1 0 0 0.01 3.26 0 0.30 85%
Spain Rajoy I 0.95 204 0.95 2 1 1 0 1.00 7.60 1 0.88 89%
Sweden Lofven I 0.99 300 0.00 0 0 0 0 0.01 3.40 1 0.11 82%
UK Cameron I 1.00 850 0.95 2 1 1 0 1.00 6.91 0 0.07 81%
European involvement in the anti-Daesh coalition 235
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orientation follows prior work in its classification (Asmus et al., 2004; Biehl et al., 2013; GMF,
2014). To be considered inside the set alliance value, a country needs to effectively show two
out of three indicators. Hence, based on the aggregate alliance index, countries with a score of
1.25 and above are considered rather inside the set alliance value, whereas scores of 2 and above
indicate full membership and less than 0.75 full non-membership. This means that all countries
that score on two or more dimensions of the index are considered fully inside the set alliance value
and those that score on a single dimension are considered rather outside the set. Table 3displays
the individual scores and the resulting fuzzy values for this condition.
Right Executive refers to governmentspolitical positions on a left-right scale. The estimate
draws on partisanship data provided by the ParlGov database (Döring and Manow, 2018), which
in turn originates from the Chapel Hill Expert Survey (CHES, Bakker et al., 2015). Since many of
the EU 28 have coalition governments, partiesindividual left-right scores and their parliamen-
tary seat share was used to calculate a weighted left-right score for the overall government.
The general left-right variable in the CHES data runs from 0 for extreme left to 10 for extreme
right. Using the direct method of calibration, this data was turned into fuzzy values where a score
of 5 is a natural cross-over, resulting in fuzzy values of 0.50, and 6 and 4 were used as upper and
lower boundaries (fully inside and fully outside the set right executive, respectively).
Parliamentary Veto Rights reflects a legislatures formal right to veto military deployments.
The key distinction is whether or not a parliament enjoys the right to debate and decide upon
military missions before the armed forces are dispatched. If such a formal veto right exists,
the respective country is coded as 1, if not it is assigned a score of 0. My estimate primarily draws
upon the ParlCon data set (Wagner et al., 2010) and subsequent updates (Wagner, 2018), as well
as data from the PAKS project (Dieterich et al., 2015).16 Of the EU 28, a total of 18 countries
have parliamentary veto rights that apply to ad hoc coalitions such as the anti-Daesh coalition.
Notably, some countries adopt different procedures depending on whether an operation takes
place within the institutional context of NATO, CFSP, or as part of an ad hoc coalition of
countries.17 Several countries have also amended their constitutions in recent years, such as
Spain, France, and Italy.18
Finally, High Threat Perception reflects European citizensattitudes towards terrorism and the
foreign fighters phenomenon and whether people believed that terrorism and foreign fighters
would pose increased security challenges for the EU in the coming years. My estimate draws
on data from a Special Eurobarometer survey on European citizensattitudes towards security
(EC, 2015). The survey was requested by the European Commission and conducted in March
2015, when the terrorist attacks on Charlie Hebdo in Paris, which occurred on January 7,
2015, were still fresh in peoples minds (EC, 2015). The survey collected responses from
28,083 Europeans across all EU member states, which makes it a suitable choice for this study.19
On average among the EU 28, 68% of the respondents said that the security challenge from
terrorism and foreign fighters was likely to increase, with responses from individual countries
ranging from 42% in Latvia and 44% in Lithuania to 79% in Germany and 80% in the
16These coding criteria mean that political conventions, such as in the UK where an informal veto right has emerged, are
not considered to have the same strength as formal war powers (see Kaarbo and Kenealy, 2017; Strong, 2018).
17One example is Bulgaria, where a constitutional ruling in 2003 effectively removed mandatory parliamentary approval for
NATO missions (Wagner et al., 2010, 39).
18In Spain the constitutional amendment after the Iraq War led to a de facto parliamentary veto right (Wagner et al., 2017).
Constitutional reform in France has given the parliament more rights, but these do not amount to a formal veto (Ostermann,
2017). Italy lacked mandatory parliamentary approval when the anti-Daesh coalition was initiated, but the situation has
changed with a new law that was passed in December 2016 (Coticchia and Vignoli, 2020).
19Survey question QA5.2 asked Would you say that the following challenges to the internal security of the EU are likely
to increase, decrease or remain unchanged over the next years? Terrorism (including the foreign fightersphenomenon)
(EC, 2015, T20).
236 Patrick A. Mello
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Netherlands. Accordingly, countries were coded as being fully insidethe set high threat percep-
tion if 70% or more of the respondents saw an increased security challenge from terrorism and
foreign fighters. The 0.50 cross-over was set at 62.5%, which effectively separates the group of
countries with average to high responses (65% and higher) from those with below-average
responses (60% and less). Scores below 50% were considered fully outsidethe set high threat
perception. Table 3lists the raw data and calibrated fuzzy values for the included conditions.
Table A1 and Figure A1 in the appendix provide additional documentation.
Set-theoretic analysis
The first stage in the analytical procedure of QCA is the testing for necessary conditions. Table 4
shows that none of the five included conditions passes the conventional threshold of 0.90 consis-
tency (Schneider and Wagemann, 2012), and thus none can be considered necessary for the
outcome of military participation in the anti-Daesh coalition. This also holds for the absence
(negation) of each of the included conditions.
Table 4. Testing for necessary conditions
Condition
Presence of condition Absence of condition
Consistency Coverage Relevance Consistency Coverage Relevance
External threat 0.777 0.647 0.816 0.270 0.144 0.428
Alliance value 0.760 0.518 0.695 0.326 0.203 0.533
Right executive 0.563 0.347 0.579 0.510 0.350 0.631
Parliamentary veto rights 0.352 0.178 0.403 0.648 0.590 0.814
Public support 0.646 0.389 0.582 0.515 0.364 0.649
Table 5. Truth table for military participation in the anti-Daesh coalition
Conditions Outcome
NConsistency PRI CountryTARVP MP
1 0 0 0 1 1 1 1.00 1.00 France
1 0 1 0 1 1 1 1.00 1.00 Belgium
1 1 0 1 1 1 1 1.00 1.00 Denmark
1 1 1 0 0 1 1 1.00 1.00 UK
1 1 1 0 1 1 1 1.00 1.00 Netherlands
1 1 0 0 0 1 1 0.97 0.96 Italy
1 1 1 1 0 1 1 0.82 0.74 Germany
0 1 1 0 0 1 1 0.80 0.72 Poland
0 1 1 0 1 0 1 0.31 0.02 Portugal
1 1 1 1 1 0 1 0.30 0.07 Spain
0 1 1 1 0 0 2 0.29 0.03 Estonia, Latvia
0 0 1 1 1 0 2 0.26 0.02 Cyprus
0 0 1 1 0 0 1 0.25 0.03 Hungary, Ireland
1 0 1 1 1 0 1 0.25 0.04 Bulgaria, Finland
0 1 0 1 1 0 2 0.22 0.06 Lithuania, Romania
1 0 0 1 0 0 1 0.21 0.04 Sweden
0 0 0 1 0 0 1 0.20 0.04 Croatia
1 0 1 1 0 0 2 0.18 0.06 Austria
0 0 0 1 1 0 3 0.17 0.02 Czech Republic, Luxembourg, Malta
0 0 1 0 0 0 1 0.13 0.03 Greece
0 0 0 0 0 0 2 0.11 0.01 Slovakia, Slovenia
Notes: T =external threat; A =alliance value; R =right executi ve; V =parliamentary veto rights; P =public support; MP =Military
Participation, bold cases hold membership >0.50 in the outcome.
Empty rows are omitted for presentational purposes (see online appendix for a table with logical remainders).
European involvement in the anti-Daesh coalition 237
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The second stage is the truth table analysis, which aims at identifying individual conditions or
combinations of conditions that consistently lead towards the outcome. Table 5displays the truth
table for the outcome military participation in the anti-Daesh coalition (MP) and the explanatory
conditions, external threat (T), alliance value (A), right executive (R), parliamentary veto
rights (V), and public threat perception (P). With five conditions, this explanatory model entails
25 =32 rows of logically possible combinations of conditions. As indicated in the table, rows 22 to
32 are omitted, because these do not contain any empirical cases. These are logical remainder
rows, which can be incorporated in the minimization to derive QCA solution terms.
As measures of fit, Table 5shows consistency, which reflects the extent to which a row
(combination of conditions) is sufficient for the outcome MP. The second indicator is PRI, which
refers to the proportional reduction in inconsistency. This measure can help to identify ambig-
uous subset relationships, which can be the case if PRI is considerably lower than consistency
(see Schneider and Wagemann, 2012, 242). To minimize the truth table and to derive solution
terms, a consistency cut-off point is set by the researcher. This indicates which rows are consid-
ered to be consistent enough to be included in the ensuing Boolean minimization procedure.
Here, an effective consistency threshold of 0.87 is used, higher than the recommended minimum
of 0.75 (Ragin, 2008, 46). This means that the top seven rows are included in the minimization
procedure. Notably, this entails all cases that show the outcome (printed in bold in Table 5)
and there are no contradictory rows with cases that show the outcome and those that do not
as part of the same configuration, which meets an important criterion for the truth table analysis
(cf. Rihoux and De Meur, 2009).
The third stage of the set-theoretic analysis with QCA is the minimization of the truth table.
Based on a Boolean minimization algorithm, the software (the QCApackage in R, Duşa, 2019)
can derive three solution terms, which differ in how they treat logical remainders, resulting in
more or less parsimonious or complex solutions. Table 1displays the intermediate solution term
for the outcome military participation in the anti-Daesh different combinations of conditions,
which are listed in the left-hand rows. I follow established notation, where black circles () refer
to the presence of a condition and crossed-out circles (‘•’) indicate a conditions absence. Below
each path are listed the measures of fit, including coverage scores. These reflect how much of the
empirical data is explained by each path. Moreover, the table lists which countries/cases are
covered by which path and which of these are solely accounted for by an individual path (bold
font). The lower end of the table details the total solution consistency and coverage, and the
number of models derived (a single model). The intermediate solution incorporated four direc-
tional expectations, which guide the inclusion of logical remainder rows, namely the presence of
an external threat (T), alliance value (A), public threat perception (P), and the absence of parlia-
mentary veto rights (V) which were expected to contribute towards the outcome. Because party
political incentives can cut both ways, as discussed above, no specific expectations were formu-
lated for this condition. The complete truth table with an indication of which logical remainders
were used for the intermediate solution as simplifying assumptions is documented in the online
appendix (Table A2).
What do the results tell us about contributions to the anti-Daesh coalition? There are four
notable findings. First, it is apparent that all solution paths contain either an external threat
(Paths 1 & 2), or alliance value (Path 3), or a combination of these two conditions (Path 1).
This underscores the relevance of international-level incentives for coalition contributions as
most of those countries that contributed militarily had foreign fighters in Iraq and Syria (many
of these countries also experienced jihadi terrorism on their own soil), and many valued their
alliance membership in NATO and their relationship with the USA. Moreover, the analysis docu-
ments the utility of a configurational perspective that integrates international- and domestic-level
factors (Bennett et al.,1997; Haesebrouck, 2018; Massie, 2019), because neither external threat nor
alliance value are sufficient on their own to bring about the outcome. Throughout the three paths,
238 Patrick A. Mello
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the two conditions combine with other push factors (Path 1 and Path 2) and with the absence of a
constraint against military involvement (Path 2 and Path 3).
Second, the results also show that many of those countries that made meaningful
military contributions do not have legislatures with an ex ante veto right over military deploy-
ments (parliamentary war powers). Precisely, it is the absence of this institutional constraint that
characterizes Path 2 and Path 3 (either in combination with an external threat and public threat
perception or together with alliance value, a right executive, and the absence of public threat
perception, respectively). This finding broadly resonates with studies that have emphasized the
relevance of parliamentary veto power on military deployments (Peters and Wagner, 2011;
Ruys et al.,2019), but which have also highlighted that there is an interaction between institutional
rules, political preferences, and the context of military missions (Wagner, 2018, 131; Mello, 2019,
49). Of those that participated militarily, only the legislatures in Germany and Denmark have
formal veto rights over military deployments (hence these two countries are uniquely covered
by Path 1 instead of Path 2), and Germany limited its involvement to air support, arguably
due to political and constitutional considerations, if the parliamentary debates in the
Bundestag following upon the terrorist attacks against Charlie Hebdo and the Bataclan are taken
as an indicator. Indeed, the German governments policy on the anti-Daesh coalition seems to
reflect the countrys traditional reluctance when it comes to military involvement and warfighting
(Brummer and Oppermann, 2016). This contrasts with Denmark, where involvement in US-led
military coalitions enjoys broad political support and has become part of the countrys strategic
culture (Jakobsen and Rynning, 2019). These political preferences also help to explain why the
institutional rules of formal parliamentary involvement on military deployments did not stop
Denmark from engaging in airstrikes against Daesh in Syria and Iraq.
Third, the analysis shows that rightist partisanship was associated with military involvement,
which resonates with the direction expected by most of the literature on party politics and security
policy (Hofmann and Martill, 2021; Wagner et al.,2017). Yet, this finding must be qualified
because a right executive features in only one of the three solution paths and this combination
is solely populated by Poland (Path 3). Moreover, when we examine Table 5, we also see that three
countries that were involved in the air strikes did not have right executives (France, Denmark, and
Italy). Based on the discussion in the theory section, this is not too surprising, because the anti-
Daesh coalition was neither a classic left-of-center military mission, like a humanitarian military
intervention (cf. Rathbun, 2004), nor a purely right-of-center strategic use of force, but a mixture
of both types of missions, where clear-cut partisan patterns are less prone to materialize, even
though a recent study on EU member statesinvolvement in military operations since the late
1990s found that left governments, by-and-large were more inclined to participatein these mili-
tary missions (Haesebrouck and Mello, 2020, 579).
Finally, public threat perception is the only condition that appears in two qualitative states in the
solution term (presence and absence of the respective condition). However, apart from the case of
Poland, public threat perception was present among all of the cases that showed the outcome
(Belgium, Denmark, France, Germany, Italy, Netherlands, and UK). As such, this pattern resonates
with the expectations derived in the theory section. While Poland was considered to be rather outside
the set public threat perception, this case contained three conditions that were directed towards mili-
tary involvement and which thus arguably outweighed the lower level of threat perception.
Drawing on public opinion data from a Special Eurobarometer survey on public perceptions of
terrorism and the foreign fighters phenomenon (EC, 2015), this paper has made a first step
towards filling a gap that previous studies identified, but which had not yet been addressed with
comparative data (Haesebrouck, 2018; Saideman, 2016). That said, public opinion on foreign and
security policy, and especially on military missions, is notoriously difficult to measure. This is one
reason why many comparative studies have not taken it into account, even though it is often
acknowledged as an important factor to consider. To further explore this factor, future work could
focus on the development of public opinion throughout the anti-Daesh coalition, among a
European involvement in the anti-Daesh coalition 239
https://doi.org/10.1017/S1755773921000333 Published online by Cambridge University Press
smaller subset of EU member states, where more fine-grained data might be available. Such an
approach was taken, for instance, in a temporal comparison of public support for military involve-
ment during the Afghanistan missions of Canada and Germany throughout the ISAF mission
(Lagassé and Mello, 2018).
Conclusion
This paper has analyzed military contributions from the EU 28 to the anti-Daesh coalition in
Iraq and Syria. The results of the configurational analysis highlight the importance of external
threats and alliance considerations, as well as the policy relevance of institutional constraints,
particularly legislative veto rights. Concerning the former, all countries that contributed militarily
to the airstrikes did so either under the presence of an external threat, as when some of their own
citizens joined Daesh as foreign fighters, or because of alliance considerations. This broadly reso-
nates with expectations formulated in realist-inspired empirical work on state behavior with
regard to military coalitions (Davidson, 2014; Pedersen and Reykers, 2020). Yet, it is also clear
that domestic factors cannot be disregarded, especially institutional constraints like parliamentary
war powers (Peters and Wagner, 2011; Ruys et al.,2019). These seem to have posed an effective
constraint on executive decision-making, as only two countries with a legislative veto on military
deployments, Denmark and Germany, participated in the airstrikes, and the latter restricted its
military involvement to air support functions, arguably for political reasons. In Denmark, the
broad political support for expeditionary warfare and involvement in US-led coalitions arguably
outweighed the institutional constraint posed by mandatory parliamentary involvement.
Clearly, and this appears to be a broader trend beyond operation Inherent Resolve, govern-
ments seek the added legitimacy of parliamentary approval, also in countries where parliament is
not formally involved in security policy and where there is no obligation on executives to debate
and vote on missions. Among others, this was the case in Belgium and the UK, where involvement
in the anti-Daesh coalition was decided upon by parliament (Strong, 2018; Fonck et al., 2019).
Notably, partisanship did not yield pronounced patterns. In the light of prior studiesresults,
this is not too surprising, because the anti-Daesh coalition did not constitute a traditional
left-of-center military mission, as in a humanitarian military intervention, nor was it driven purely
by strategic considerations, which the political right would support. Instead, the military coalition
was a mixture of both types of missions, where clear-cut partisan patterns should not be expected.
However, as Hofmann and Martill (2021, 322) acknowledge in a recent review, party politics is
more variegated in its effects than we might wish to accept. Hence, the failure to detect clear-cut
patterns of partisanship should not be taken to imply that party politics did not matter for
decision-making during the anti-Daesh coalition.
With its focus on providing a European comparison of military contributions and a framework
of five international- and domestic-level factors, it was beyond the scope of this paper to explore
the multidimensional nature of the fight against Daesh. Prospective studies could complement this
with a comparison of humanitarian aid and capacity-building efforts in the region. Moreover,
emphasis could be placed on the human security dimension of the airstrikes, investigating the
conditions under which civilian deaths occurred and comparing the accountability mechanisms
of the involved countries.20 Finally, another aspect that deserves a focused treatment is the time
dimension, taking into account the entry and exit of various allies throughout the military
campaign, as we know that coalition withdrawal often occurs as a function of domestic politics.
Recent studies have covered this at the individual case level, for instance for the war in Iraq
(McInnis, 2019; Mello, 2020). Here, it would be worthwhile to explore whether similar dynamics
also occurred during the coalition against Daesh. Finally, as mentioned at the outset of this paper,
the anti-Daesh coalition received support from more than 70 states and five international
20The UK-based NGO Airwars.orghas collected a host of data on both aspects.
240 Patrick A. Mello
https://doi.org/10.1017/S1755773921000333 Published online by Cambridge University Press
organizations. Future studies could explore the involvement of other groups of countries, for
instance in the MENA region and sub-Saharan Africa, also with focused comparisons between
democracies and non-democracies among those involved in the coalition.
Supplementary material. To view supplementary material for this article, please visit https://doi.org/10.1017/S17557739
21000333.
Acknowledgements. I would like to thank Amos Fox, James Rogers, and the three anonymous reviewers for their helpful
comments on earlier versions of this article. For research assistance during the initial stages, I am grateful to Danielle Al-Qassir
and Teslin Augustine.
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Cite this article: Mello PA (2022). Incentives and constraints: a configurational account of European involvement in the anti-
Daesh coalition. European Political Science Review 14, 226244. https://doi.org/10.1017/S1755773921000333
244 Patrick A. Mello
https://doi.org/10.1017/S1755773921000333 Published online by Cambridge University Press
... As in other fields of the social sciences, a majority of FPA studies using QCA are situated at the country level, comparing across a medium number of states. Examples include democracies' involvement and non-involvement in the Iraq War of 2003 (Mello 2012(Mello , 2014, countries' participation in the multilateral coalition against the "Islamic State" (Haesebrouck 2018;, NATO burden sharing in Libya (Haesebrouck 2017b), the role of junior partners in coalition warfare (Schmitt 2018), the political contestation of military missions (Haesebrouck and van Immerseel 2020), the implementation of sanctions against "Arab Spring" countries in the Middle East and North Africa (Boogaerts 2018;Boogaerts and Drieskens 2020), the occurrence of unintended consequences of UN sanctions in targeted states (Meissner and Mello 2022), and the allocation of the foreign ministry to junior partners in governing coalitions of parliamentary democracies (Oppermann and Brummer 2020). Other studies operate at different levels, for instance examining the influence of ethnic identity groups on U.S. foreign policy (Rubenzer 2008), the inclusion of human rights in territorial peace agreements (Caspersen 2019), the conditions under which democratic leaders' opted for defection from the multilateral Iraq War coalition (Mello 2020), the foreign policy behavior of Brazil in various international crises (de Sá Guimarães and de Almeida 2017), agency slack within UN organizations (Heldt et al. 2022), military intervention in Africa (Kisangani and Pickering 2022), conceptions of international order, as expressed in Australian and Chinese policy documents (van Nieuwenhuizen 2019), and even international arbitration under Hellenistic rulers in ancient times (Grynaviski and Hsieh 2015). ...
... As in other fields of the social sciences, a majority of FPA studies using QCA are situated at the country level, comparing across a medium number of states. Examples include democracies' involvement and non-involvement in the Iraq War of 2003 (Mello 2012(Mello , 2014, countries' participation in the multilateral coalition against the "Islamic State" (Haesebrouck 2018;, NATO burden sharing in Libya (Haesebrouck 2017b), the role of junior partners in coalition warfare (Schmitt 2018), the political contestation of military missions (Haesebrouck and van Immerseel 2020), the implementation of sanctions against "Arab Spring" countries in the Middle East and North Africa (Boogaerts 2018;Boogaerts and Drieskens 2020), the occurrence of unintended consequences of UN sanctions in targeted states (Meissner and Mello 2022), and the allocation of the foreign ministry to junior partners in governing coalitions of parliamentary democracies (Oppermann and Brummer 2020). Other studies operate at different levels, for instance examining the influence of ethnic identity groups on U.S. foreign policy (Rubenzer 2008), the inclusion of human rights in territorial peace agreements (Caspersen 2019), the conditions under which democratic leaders' opted for defection from the multilateral Iraq War coalition (Mello 2020), the foreign policy behavior of Brazil in various international crises (de Sá Guimarães and de Almeida 2017), agency slack within UN organizations (Heldt et al. 2022), military intervention in Africa (Kisangani and Pickering 2022), conceptions of international order, as expressed in Australian and Chinese policy documents (van Nieuwenhuizen 2019), and even international arbitration under Hellenistic rulers in ancient times (Grynaviski and Hsieh 2015). ...
... 14 Finally, it must be highlighted that despite its rigorous structure, QCA allows for ample flexibility in tailoring the analysis to the requirements of an individual research project. As such, the method can be used with qualitative and quantitative types of data, in small to large settings and with various forms of analytical steps and approaches (Mello 2021(Mello , 2017Schneider and Wagemann 2012;Rihoux and Ragin 2009;Pagliarin, La Mendola, and Vis 2022). But the method is not without limitations. ...
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