Exploring the Driving Forces Behind Iran’s Nuclear Deterrence Strategy: A Novel Methodological Approach

ABSTRACT

The perplexing nature of Iran’s nuclear program is evident in its simultaneous growth of enrichment capacity and the concurrent denial of any aspirations toward nuclear weapons development. This conundrum calls for a rigorous examination of Iran’s deterrence policy and the identification of obstacles hindering the adoption of a nuclear deterrence strategy. The present study’s contribution is thus twofold. Firstly, employing a Systematic Literature Review (SLR) and the Delphi technique, it delves into the intricacies of Iran’s nuclear policy and identifies thirteen driving factors inhibiting the development of nuclear weapons. Secondly, by employing the DEMATEL technique, the article determines the importance of individual factors on Iran’s nuclear strategy as well as the causal relations among them. This study, which draws on the analysis of original data, concludes by highlighting the pivotal role of the Shia religion and the ideology of leaders in Iran’s way of war and deterrence strategy.

KEYWORDS:

• Deterrence
• Iran
• nuclear weapon
• ballistic missiles
• asymmetric war

Introduction

The Iranian leadership consistently claims that Iran’s military strategy is essentially defensive, relying on deterrence for the safekeeping of the country in the face of external threats (Ajili and Rouhi 2019; Eslami and Vieira 2020, 2022, 2023). However, the United States, Israel, and Arab countries around the Persian Gulf have always seen Iran as their first-class threat (Ghanbari Jahromi 2015; A. M. Tabatabai and Samuel 2017; Takeyh 2003), especially following the development of Iran’s nuclear program since 2003 and its enrichment of uranium to 84% in 2023 that occurred alongside the rapid advancement of Iran’s intercontinental ballistic missile, hypersonic munitions, and drone programs¹ (Eslami 2021, 2022).

This research investigates an internal view of Iran’s nuclear policy, decodes the black box of Iran’s strategy to deter its adversaries, and explains why and under what circumstances Iran has adopted this strategy and not others. After the US invasion of Iraq in 2003, “deterrence” (bazdarandegi) has been one of the key concepts in the statements of Iranian officials. There is a great deal of confusion, however, about the concept of deterrence in Iran. Reviewing the existing literature on Iran’s deterrence policy demonstrates two main research streams in the field. The first group of scholars claim that a sense of threat and insecurity has pushed Iran towards adopting a nuclear deterrence. Accordingly, Iran is developing or would need to develop nuclear weapons sooner or later (Dobbins 2011; Duus 2011; Edelman, Krepinevich, and Montgomery 2011; Evron 2008; Guldimann 2023; Guzansky and Golov 2015; Parasiliti 2009; S. Sagan, Waltz, and Betts 2007; Waltz 2012). The second group of researchers argues that Iran’s deterrence concept is independent of Iran’s nuclear program. To them, Iran’s deterrence is highly dependent on asymmetric ways of war, including ballistic missiles, proxies, drones, naval guerilla warfare, and cyber technologies (Ahmadian and Mohseni 2019, 2021; Ajili and Rouhi 2019; Freedman 2017; Olson 2016). This research is positioned in the second group of studies acknowledging that nuclear bombs are considered prohibited in Iran, and the country has decided to adopt a conventional (non-nuclear) deterrence against its adversaries. There is still a gap in Iranian security studies, however, which needs to be filled through systematic and comprehensive research. In particular, while most recent studies have been devoted to explaining how to deter Iran from acquiring nuclear bombs (Alcaro 2021; Byman 2018; Dalton 2017; Edelman, Krepinevich, and Montgomery 2011; Hicks and Dalton 2017; Katzman, McInnis, and Thomas 2020; Kaye and Wehrey 2023; Mandelbaum 2015; A. Tabatabai 2019), research explaining what kind of factors have been preventing Iran from adopting a nuclear deterrence have been rare.²

Aiming to identify the main factors preventing Iran from adopting nuclear deterrence, and to understand the impact of individual factors on Iran’s deterrence strategy, the present contribution draws on a mixed method of analysis. The aspiration to provide a more systematic account of Iran’s nuclear policy is in line with the most recent tendency to employ quantitative methods in security studies (Eslami, Sotudehfar, et al. 2021; Johnston 2016; Kaltenthaler, Silverman, and Dagher 2020; Liberman and Skitka 2019; Macdonald and Schneider 2019; Quek and Johnston 2017; S. D. Sagan and Valentino 2017). This innovative method of analysis was developed in three main phases: (1) a Systematic Literature Review (SLR), (extracting the elements preventing Iran from adopting a nuclear deterrence strategy from the existing literature); (2) Delphi technique (validating the findings by a panel of experts); and (3) survey (distributed among eighteen experts and evaluated through a DEMATEL technique), which demonstrates the impact of each factor on Iran’s nuclear deterrence and identifies the most influential factors driving Iran’s conventional deterrence and causal relationships among them.

While the subject of the forthcoming research is specialized and narrow, the number of people who have the necessary knowledge and background to participate in this research is limited. Accordingly, only two groups of Iranian experts were considered to be qualified participants in this study and the respondents to this survey. First, Iranian scholars with at least 15 years of experience in the field of security studies with an established record of publications on Iran’s nuclear strategy. Second, Iranian generals with the experience of participation and command of military operations during the Iran-Iraq war, in fighting ISIS, or others with the experience of participation and command of regional and extra-regional military missions and operations (mostasharane nezami). To this end, and in line with the mentioned standards, 27 experts were identified and contacted, of which 67%, corresponding to 18 experts, agreed to respond to study questionnaires.

This article is structured as follows. It begins with a short overview of Iran’s perspective on deterrence. It then explains and justifies the methodological approach, with the three steps of the proposed analysis discussed in three subsequent sub-sections. Finally, the article draws on the findings of the analysis and introduces factors preventing Iran from adopting nuclear deterrence and demonstrate the causal relations among them. The last section concludes.

Iran’s Concept of Deterrence

Before the revolution, Iran was one of America’s closest allies in the Middle East. The United States had considered no restrictions on the supply of weapons to Iran in order to prevent the influence of communism in Iran and the Middle East (Blight et al. 2012; Dolatabadi 2017). Accordingly, the United States had promised to meet Iran’s defense needs, provided that Iran made no attempt to acquire a nuclear weapon (Adib-Moghaddam 2006; Olson 2016; Shannon 2019). After the 1979 revolution, Iran’s foreign and security policy changed towards a new, anti-Western and hardline orientation (Adib-Moghaddam 2005).

The Islamic Revolution, which has been underpinned by the notion of religious democracy (mardom salari dini) complemented with velayat e faqih (the rule of Jurisprudence), has been inherently denying the interests of the great powers and opposing the existing world order (Ghamari-Tabrizi 2014; Murray 2009), with many international actors openly opposing Iran’s views in the international arena. Strategic challenges of post-Revolution Iran started immediately with the war with Iraq, followed by the war against terrorism and ISIS and proxy wars in the region (Eslami, Bazrafshan, Sedaghat, et al. 2021). However, the country has always been facing a comprehensive threat from the United States and Israel (Barzegar 2014; Chubin 2014; Connell 2010; Ghanbari Jahromi 2015). Nowadays, Iran is surrounded by many American military bases on the ground and many warships and submarines in the sea. This reality, in addition to the existing sense of threat and insecurity that was fostered especially by the experience of war with Iraq, has been pushing Iran to pay constant attention to its deterrence capabilities (Ajili and Rouhi 2019; Aminian and Zamiri-Jirsarai 2016; Papageorgiou, Eslami, and Duarte 2023; A. Tabatabai 2019; A. M. Tabatabai and Samuel 2017; Vieira 2023; Ward 2005)

After 2003 and the US attack on Iraq, the US invasion of Iran became Iran’s main threat. At the same time, the potential threat from Israel has always existed in Iran’s defense perception (Connell 2010; Czulda 2016; Taremi 2005). Adjusting its approach, by 2005, Iran developed the so-called “mosaic defense” doctrine. Besides a focus on naval and air-defense capabilities to disrupt the enemy’s control of the sea and air lanes, “mosaic defense” essentially employs an asymmetrical approach by the IRGC and the Army (Artesh), through the mobilization of a large, dispersed militia force to engage in attritional warfare against the invading forces (Ajili and Rouhi 2019; Olson 2016; Vatanka 2004). Iran’s uranium enrichment emerged in 2003 as a means of deterrence, however, in parallel with Iran’s security and defense programs.

While the emergence of terrorist groups in the region and insecurity in the borders of Iran affected Iran’s military behavior, several indicators attest that Iran has, since 2012, been changing its defensive/deterrent system, adding an offensive dimension by relying on hybrid warfare (Chubin 2009; Ghanbari Jahromi 2015; A. Tabatabai 2019; Yossef 2019). The associated “forward defense” doctrine implies that Iran should fight its opponents outside its borders to prevent conflict inside Iran (Olson 2016; Ajili and Rouhi 2019; Eslami and Al-Marashi 2023; Akbarzadeh, Gourlay, and Ehteshami 2023. Today, five main dimensions illustrate the nature of this deterrence policy and its offensive approach: ballistic missiles, proxies, drone and naval guerilla warfare, and cyber (Ajili and Rouhi 2019; Aminian and Zamiri-Jirsarai 2016; Connell 2010; Olson 2016).

However, Iran’s reliance on asymmetric ways of wars as a form of conventional deterrence has not implied that the country has disregarded the role of its nuclear program in its deterrence strategy. In other words, while there has been no concrete evidence of Iran’s intentions to develop nuclear weapons, the enrichment of uranium at a high level since 2003 has indicated Iran’s readiness to develop a clear military dimension of its ostensibly peaceful nuclear program. In this vein, under the guidance of Ayatollah Khamenei, Iran has devised a distinct approach to deterrence that has been leveraging the benefits of nuclear programs as a means of deterrence while simultaneously avoiding the strategic disadvantages stemming from the possession of actual nuclear weapons (Kazemzadeh 2020).

Analytical Framework: A Novel Methodological Approach

The main questions guiding the present study are (1) What factors prevent Iran from adopting a nuclear deterrence strategy? and, (2) What are the causal relations between the factors that prevent Iran from adopting a nuclear deterrence strategy?

To address the two research questions, the study employs a mixed-method approach (Johnson, Onwuegbuzie, and Turner 2007). Accordingly, it draws on a Systematic Literature Review (SLR) and Delphi technique to answer the first research question (Bench and Day 2010) and the DEMATEL technique to explore the causal relationships between the identified and validated factors (associated with the second research question). In this line, deploying the SLR serves to extract and identify the elements preventing Iran from adopting a nuclear deterrence strategy from the existing literature. The Delphi technique validates the identified factors and adding some missing elements in the existing literature by a panel of experts, and DEMATEL demonstrates the causal relations between the validated factors based on a data collected through an original survey of 18 experts.

A: Systematic Literature Review (SLR)

The state of the art on Iran’s deterrence policy demonstrates a number of elements driving Iran’s deterrence policy. Aiming to identify the factors preventing Iran from adopting a nuclear deterrence, a SLR was conducted (Paul et al. 2021). The SLR is “a specific methodology that locates existing studies, selects and evaluates contributions, analyses and synthesizes data, and reports the evidence in such a way that allows reasonably clear conclusions to be reached about what is known and what is not known” (Denyer and Tranfield 2009, 672). To this end, in the first stage of the SLR, eighty-nine studies about Iran which involve “deterrence” in their title or keywords and were published in main domestic and international databases within the time period of 2005–2023 were reviewed (see Table 1).

Table 1. SLR algorithm.

#	Main activity	Explanation
1	Keywords	Deterrence, Nuclear Deterrence, Containment
2	Context	Iran
3	Database selection	Web of Science, Google Scholar, Scopus, Sid.ir, Noormags, Magiran
4	Research language	English and Persian
5	Scientific standard	Peer-reviewed journals
6	Time period	2005 to 2023

In the second phase of the SLR, all existing studies were screened. The studies were filtered through context evaluation, scientific standard, time period, and line of argument. While excluding book chapters, think tank articles, conference papers, studies that were conducted before 2005, in addition to studies claiming that Iran’s deterrence predominantly is or tends to be nuclear, sixteen peer-reviewed articles were selected as the point of departure for extracting the main factors preventing Iran from adopting a nuclear deterrence strategy (see Table 2).

Table 2. Studies found through the SLR review algorithm.

#	Main activity	Number of studies after the main activity	Excluded papers
1	Keyword and context	89	0
2	Scientific standard (only peer-reviewed articles)	38	51
3	Time limits	31	7
4	Argument screening	16	15

Focusing on the selected studies, a set of twelve factors preventing Iran from adopting a nuclear deterrence strategy were identified. According to the research conducted by local and international scholars, (1) international organizations such as the United Nations, (2) international agreements such as the Nuclear Non-Proliferation Treaty (NPT) and the Joint Comprehensive Plan of Action (JCPOA), (3) international pressures and threats including sanctions, (4) Shia religion, (5) no need for nuclear deterrence, (6) relying on conventional deterrence, (7) international security environment, (8) cost-benefit considerations, (9) the strategic culture of Iran, (10) cognitive decision-making process in Iran, (11) the ideology of the leaders, and (12) asymmetrical deterrence capabilities are the main factors deterring Iran from development of nuclear weapons (see Appendix 1).

The main criticism regarding the resulting set of twelve factors is their exact number and the subjectivity underpinning their selection. As such, the extracted factors need to be validated by a panel of experts through the Delphi technique before conducting the quantitative analysis.

B: Delphi Technique

The Delphi method provides a structured group communication process for a panel of experts to reach a consensus in collectively evaluating evidence and providing expert judgments. The method comprises two or more rounds of structured questionnaires, each followed by aggregation of responses and anonymous feedback to the participants (Mukherjee et al. 2015; Sablatzky 2022).

Aiming to measure the perception of experts regarding individual factors preventing Iran from developing a nuclear deterrence strategy, the study employed a Likert scale from 1 (for completely disagree) to 5 (completely agree). According to Musa et al. (2019), if the average of experts’ responses is more than 3.5, it can be inferred that the experts validate the factors. The rounds will be continued to the point that Kendall’s coefficient of each round reaches at 0.8 and this would be the stop point. In this research, four rounds of questionnaires were carried out with eighteen experts in February 2021 (Table 3).

Table 3. The result of Delphi method after four rounds of survey.

#	Questions	R1 Mean	R2 Mean	R3 Mean	R4 Mean	Kendall’s Coefficient	Final result
1	Diplomacy and international agreements (NPT-JCPOA)	3.517	3.615	3.640	3.641	0.85	Approved
2	Cost-benefit considerations	4.129	4.165	4.171	4.179	0.87	Approved
3	International pressures (economic sanctions)	3.832	3.836	3.847	3.852	0.82	Approved
4	International organizations	3.509	3.511	3.525	3.549	0.83	Approved
5	Strategic culture of Iran	4.006	4.108	4.160	4.175	0.83	Approved
6	Asymmetric ways of warfare	4.018	4.053	4.106	4.119	0.85	Approved
7	Relying on conventional deterrence (via BMP)	Merged (66%)	——–	———	———	———	Merged
8	Shia religion	4.186	4.289	4.352	4.365	0.84	Approved
9	Cognitive decision-making process	3.673	3.688	3.691	3.709	0.86	Approved
10	The ideology of the leaders	3.919	3.925	3.994	4.003	0.82	Approved
11	International security environment	3.506	3.520	3.521	3.521	0.83	Approved
12	No need of Iran to nuclear deterrence	Omitted (83%)	———	———	———	———	Omitted
13	Lack of financial resources	———	3.875	3.881	3.884	0.80	Approved
14	Scientific weakness	———	3.611	3.619	3.625	0.81	Approved
15	Iran’s logic to prevent the formation of nuclear competition in the region	———	3.856	3.955	3.981	0.81	Approved
16	Public objection against weapons of mass destruction	———	3.001	3.020	3.106	0.80	Disapproved

In addition to providing their perceptions on the factors identified in the SLR, the panel of experts suggested the inclusion of four new factors in the initial round of the Delphi survey. These factors are (1) the lack of financial resources for research and development, (2) scientific weakness and lack of access to scientific databases, (3) Iran’s logic/aspiration to prevent the formation of a nuclear competition in the region, and (4) public objection against weapons of mass destruction (WMDs). These four factors were incorporated into the second round of the Delphi survey.

Additionally, during the first round, 66% of the experts believed that “relying on conventional deterrence (via BMP)” should be merged with “asymmetrical deterrence capabilities and method of warfare of Iran”. Taking this into account, factor number 6 and 7 were combined. Furthermore, 83% of the experts considered “No need of Iran for nuclear deterrence” to be a consequence of Iran’s current deterrence strategy rather than a cause of it, and, therefore, this factor was excluded from the questionnaire based on their recommendation.

After distributing four rounds of questionnaires to eighteen experts, it was found that there was disagreement regarding the significance of “Public objection against WMDs” as a factor preventing Iran from adopting a nuclear deterrence strategy. The final average score for this factor was calculated to be 3.106, which is below the threshold of 3.5. Consequently, all experts agreed on the remaining thirteen factors that are considered the main drivers behind Iran’s deterrence strategy. The final list of factors preventing Iran from developing nuclear weapons determined through the Delphi method is presented in Tables 3 and 4.

Table 4. Factors preventing Iran’s nuclear deterrence.

#	Questions
D1	Diplomacy and international agreements (NPT-JCPOA)
D2	Cost-benefit considerations
D3	International pressures including economic sanctions and financial threats
D4	International organizations and Institutions
D5	Strategic culture of Iran
D6	Asymmetrical deterrence capabilities and method of warfare of Iran
D7	Shia religion
D8	Cognitive decision-making process
D9	Ideology of the leaders
D10	International security environment
D11	Lack of financial resources for research and development
D12	Scientific weakness and lack access to scientific databases
D13	Iran’s logic to prevent formation of a nuclear competition in the region

C: Dematel

Although the first research question guiding the present study has been responded to in the previous section (Table 4), the second question remains unanswered. Aiming to understand which factor has the most impact in preventing Iran from adaptation of nuclear deterrence and determine the causal relationship among identified factors, the DEMATEL technique was employed.

The Decision-Making Trial and Evaluation Laboratory (DEMATEL) method (Fontela and Gabus 1976) is an improvised type of structural modeling approach. This technique is a structuring tool used for analyzing and understanding the cause-and-effect relationship among factors under consideration (Tsui, Tzeng, and Wen 2015). The knowledge of decision-makers is incorporated in the method to develop a cause-and-effect diagram that shows the influence of each factor on another (Keskin 2015).

DEMATEL is one of the techniques of Soft Operational Research (SOR). This technique aims to identify and create awareness about the relationships between the components of phenomena, not to generalize the results in terms of statistical probabilities.

As problem structure methods such as DEMATEL and Delphi rely on the opinions of experts to explain the relationships between factors (Azar, Khosravani, and Jalali 2019; Chung-Wei and Gwo-Hshiung 2009), data was gathered from a limited number of experts in the specific field of study. It should be noted that the findings obtained through this approach heavily depend on the experts’ perception of the phenomena under investigation. Therefore, if data were collected from different experts, the results could potentially vary. The main strategy of the present study was to distribute the questionnaire among the most qualified available experts who are considered to be the representatives of Iran’s internal debate on deterrence strategy. In March 2022, the DEMATEL questionnaire was distributed to a panel consisting of eighteen experts.

To deploy the DEMATEL technique, a pair-wise questionnaire was designed and distributed it among eighteen experts (including seven military experts and eleven academic experts) in the field of Iran’s nuclear policy. In line with this, the experts demonstrated the impact of individual elements of Iran’s deterrence policy on the other elements and showed the causal relationships among them (see the questionnaire in appendix 4).

The data was analyzed based on the following steps:

Step 1:

In the first step of my DEMATEL analysis, the initial relationship matrix was generated for each expert using Equation (1)(1) $a_{\mathit{ij}}=\frac{1}{H}\sum _{\mathit{k}=1}^H{x}_{ij}^k$(1) . The matrix is a pair-wise comparison generated using the scale (0 – No influence, 1 – Very low influence, 2 – Low influence, 3 – Medium influence, 4 – High influence, 5 – Very high influence), to depict the interrelationship of factors. The notation of x_ij indicates the degree to which the respondent believes factor i affects factor j. For i = j, the diagonal elements are set to zero.

In total, k matrices are obtained where k represents the number of experts:

$A^k=\left[x_{ij}^k\right]$

The overall direct relationship matrix A is obtained as follows:

$\mathit{A}=\left[a_{\mathit{ij}}\right]$

(1) $a_{\mathit{ij}}=\frac{1}{H}\sum _{\mathit{k}=1}^H{x}_{ij}^k$(1)

The average matrix A (presented in Table 5) can be constructed based on Equation 1(1) $a_{\mathit{ij}}=\frac{1}{H}\sum _{\mathit{k}=1}^H{x}_{ij}^k$(1) :

Table 5. The average matrix A.

	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13
D1	0	1.83	3.79	1.82	3.77	3.02	0.55	2.87	0.99	3.74	3.89	4.27	1.87
D2	4.11	0	1.42	0.89	1.17	3.89	0.49	3.77	1.26	2.35	1.92	1.15	4.52
D3	4.72	4.89	0	2.17	3.61	3.82	0.61	3.86	2.47	1.25	4.78	4.51	1.25
D4	4.59	3.25	4.29	0	1.04	3.07	0.61	3.01	0.61	4.16	3.47	2.17	2.16
D5	4.61	4.21	1.17	1.97	0	4.85	0.56	4.31	3.85	3.15	0.61	2.78	3.89
D6	3.98	4.15	4.16	3.89	4.10	0	0.56	0.95	0.79	3.77	1.78	1.25	3.56
D7	4.72	4.83	2.96	0.56	4.95	4.87	0	4.58	5	4.51	0.55	1.5	4.39
D8	4.63	3.98	2.06	0.84	1.49	3.11	0.56	0	1.25	1.67	0.88	0.91	3.49
D9	4.82	4.79	3.28	2.75	4.52	3.55	1.34	4.15	0	3.56	0.52	0.55	4.27
D10	3.79	3.67	4.21	3.96	4.67	4.31	0.78	2.85	1.93	0	2.98	2.43	4.21
D11	0.52	4.16	0.93	0.15	0.55	3.75	0.61	1.08	0.61	1.26	0	3.89	0.78
D12	1.17	3.15	0.62	0.07	0.81	3.56	0.75	0.35	0.78	0.92	1.19	0	0.42
D13	3.75	4.66	1.06	2.55	1.95	4.07	0.52	1.78	1.19	3.38	0.56	0.44	0

Each item in Table 6 of matrix represents the average of experts’ opinion towards pairwise comparisons of individual factors.

Table 6. The normalized initial direct-relation matrix.

	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13
D1	0.000	0.042	0.087	0.042	0.087	0.070	0.013	0.066	0.023	0.086	0.090	0.098	0.043
D2	0.095	0.000	0.033	0.021	0.027	0.090	0.011	0.087	0.029	0.054	0.044	0.027	0.104
D3	0.109	0.113	0.000	0.050	0.083	0.088	0.014	0.089	0.057	0.029	0.110	0.104	0.029
D4	0.106	0.075	0.099	0.000	0.024	0.071	0.014	0.069	0.014	0.096	0.080	0.050	0.050
D5	0.106	0.097	0.027	0.045	0.000	0.112	0.013	0.099	0.089	0.073	0.014	0.064	0.090
D6	0.092	0.096	0.096	0.090	0.094	0.000	0.013	0.022	0.018	0.087	0.041	0.029	0.082
D7	0.109	0.111	0.068	0.013	0.114	0.112	0.000	0.106	0.115	0.104	0.013	0.035	0.101
D8	0.107	0.092	0.047	0.019	0.034	0.072	0.013	0.000	0.029	0.039	0.020	0.021	0.080
D9	0.111	0.110	0.076	0.063	0.104	0.082	0.031	0.096	0.000	0.082	0.012	0.013	0.098
D10	0.087	0.085	0.097	0.091	0.108	0.099	0.018	0.066	0.044	0.000	0.069	0.056	0.097
D11	0.012	0.096	0.021	0.004	0.013	0.086	0.014	0.025	0.014	0.029	0.000	0.090	0.018
D12	0.027	0.073	0.014	0.002	0.019	0.082	0.017	0.008	0.018	0.021	0.027	0.000	0.010
D13	0.086	0.107	0.024	0.059	0.045	0.094	0.012	0.041	0.027	0.078	0.013	0.010	0.000

Step 2:

The normalized initial direct-relation matrix is calculated according to the following equation: Equation 2(2) $\mathit{S}=\frac{1}{{\sum }^{\mathit{j}=1}\mathit{n}{a}_{\mathit{ij}}}$(2)

(2) $\mathit{S}=\frac{1}{{\sum }^{\mathit{j}=1}\mathit{n}{a}_{\mathit{ij}}}$(2)

Each element in matrix D falls between zero and one.

Step 2 is to calculate the normalized initial direct-relation matrix D, depicted below (Table 6):

Each item in this table is the normalized amount of experts’ opinion towards pair-wise comparisons of individual factors. Accordingly, the result would be a number between Zero and One.

Step 3:

In the third step, the total relation matrix calculated and is defined as matrix T:Equation 3(3) $\mathit{T}=\mathit{D}{\left(\mathit{I}-\mathit{D}\right)}^{-1}$(3)

(3) $\mathit{T}=\mathit{D}{\left(\mathit{I}-\mathit{D}\right)}^{-1}$(3)

Where I is the identity matrix (Table 7).

Step 4:

The sum of the rows and the sum of columns (presented in Table 8) are calculated as given below and are separately denoted as R and C within the total-relation matrix D: Equation 4(4) $\mathit{R}={\left[r_i\right]}_{\mathit{n}\times 1}={\left[\sum _{\mathit{j}=1}^n{a}_{\mathit{ij}}\right]}_{\mathit{n}\times 1}$(4)

(4) $\mathit{R}={\left[r_i\right]}_{\mathit{n}\times 1}={\left[\sum _{\mathit{j}=1}^n{a}_{\mathit{ij}}\right]}_{\mathit{n}\times 1}$(4)

(5) $\mathit{C}={\left[c_i\right]}_{1\times \mathit{n}}={\left[\sum _{\mathit{i}=1}^n{a}_{\mathit{ij}}\right]}_{1\times \mathit{n}}$(5)

According to Equations 4(4) $\mathit{R}={\left[r_i\right]}_{\mathit{n}\times 1}={\left[\sum _{\mathit{j}=1}^n{a}_{\mathit{ij}}\right]}_{\mathit{n}\times 1}$(4) and 5(5) $\mathit{C}={\left[c_i\right]}_{1\times \mathit{n}}={\left[\sum _{\mathit{i}=1}^n{a}_{\mathit{ij}}\right]}_{1\times \mathit{n}}$(5) , each item in the body of matrix Table 9 is the amount of relationship between related i and j. In line with this, R_i stands for the sum of influences rate of each i, and C_j stands for sum of impactability of each j.

Table 7. The total relation matrix.

	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13
D1	0.000	0.042	0.087	0.042	0.087	0.070	0.013	0.066	0.023	0.086	0.090	0.098	0.043
D2	0.095	0.000	0.033	0.021	0.027	0.090	0.011	0.087	0.029	0.054	0.044	0.027	0.104
D3	0.109	0.113	0.000	0.050	0.083	0.088	0.014	0.089	0.057	0.029	0.110	0.104	0.029
D4	0.106	0.075	0.099	0.000	0.024	0.071	0.014	0.069	0.014	0.096	0.080	0.050	0.050
D5	0.106	0.097	0.027	0.045	0.000	0.112	0.013	0.099	0.089	0.073	0.014	0.064	0.090
D6	0.092	0.096	0.096	0.090	0.094	0.000	0.013	0.022	0.018	0.087	0.041	0.029	0.082
D7	0.109	0.111	0.068	0.013	0.114	0.112	0.000	0.106	0.115	0.104	0.013	0.035	0.101
D8	0.107	0.092	0.047	0.019	0.034	0.072	0.013	0.000	0.029	0.039	0.020	0.021	0.080
D9	0.111	0.110	0.076	0.063	0.104	0.082	0.031	0.096	0.000	0.082	0.012	0.013	0.098
D10	0.087	0.085	0.097	0.091	0.108	0.099	0.018	0.066	0.044	0.000	0.069	0.056	0.097
D11	0.012	0.096	0.021	0.004	0.013	0.086	0.014	0.025	0.014	0.029	0.000	0.090	0.018
D12	0.027	0.073	0.014	0.002	0.019	0.082	0.017	0.008	0.018	0.021	0.027	0.000	0.010
D13	0.086	0.107	0.024	0.059	0.045	0.094	0.012	0.041	0.027	0.078	0.013	0.010	0.000

Table 8. Calculation of R and C.

	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13	R
D1	0.187	0.237	0.209	0.141	0.216	0.258	0.047	0.198	0.104	0.218	0.194	0.212	0.187	2.408
D2	0.251	0.167	0.145	0.110	0.145	0.245	0.040	0.197	0.095	0.175	0.135	0.123	0.225	2.053
D3	0.313	0.324	0.145	0.158	0.228	0.298	0.053	0.238	0.144	0.188	0.226	0.231	0.196	2.742
D4	0.290	0.267	0.226	0.104	0.164	0.260	0.049	0.205	0.095	0.231	0.193	0.172	0.196	2.451
D5	0.320	0.312	0.180	0.164	0.160	0.320	0.053	0.251	0.174	0.235	0.137	0.187	0.259	2.751
D6	0.292	0.296	0.230	0.196	0.235	0.206	0.049	0.175	0.107	0.235	0.162	0.157	0.236	2.576
D7	0.382	0.383	0.254	0.166	0.311	0.378	0.050	0.303	0.229	0.305	0.165	0.194	0.318	3.438
D8	0.254	0.240	0.152	0.104	0.146	0.221	0.040	0.113	0.092	0.154	0.110	0.114	0.197	1.937
D9	0.349	0.345	0.237	0.191	0.271	0.316	0.072	0.268	0.104	0.259	0.150	0.157	0.284	3.002
D10	0.322	0.324	0.254	0.214	0.270	0.332	0.060	0.237	0.144	0.180	0.203	0.200	0.276	3.016
D11	0.116	0.196	0.091	0.059	0.087	0.186	0.033	0.097	0.057	0.105	0.058	0.146	0.101	1.332
D12	0.112	0.156	0.074	0.050	0.082	0.163	0.032	0.071	0.054	0.086	0.075	0.051	0.081	1.086
D13	0.248	0.264	0.142	0.148	0.164	0.251	0.041	0.161	0.095	0.200	0.110	0.110	0.134	2.067
C	3.437	3.510	2.338	1.805	2.479	3.433	0.620	2.511	1.494	2.573	1.917	2.053	2.691

Table 9. Causal relations among the factors.

	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10	D11	D12	D13
D1	1	1	1	0	1	1	0	1	0	1	1	1	1
D2	1	0	0	0	0	1	0	1	0	0	0	0	1
D3	1	1	0	0	1	1	0	1	0	1	1	1	1
D4	1	1	1	0	0	1	0	1	0	1	1	0	1
D5	1	1	0	0	0	1	0	1	0	1	0	1	1
D6	1	1	1	1	1	1	0	0	0	1	0	0	1
D7	1	1	1	0	1	1	0	1	1	1	0	1	1
D8	1	1	0	0	0	1	0	0	0	0	0	0	1
D9	1	1	1	1	1	1	0	1	0	1	0	0	1
D10	1	1	1	1	1	1	0	1	0	0	1	1	1
D11	0	1	0	0	0	1	0	0	0	0	0	0	0
D12	0	0	0	0	0	0	0	0	0	0	0	0	0
D13	1	1	0	0	0	1	0	0	0	1	0	0	0

Step 5:

A threshold value to obtain the digraph is set up in step 5. Since matrix T provides information on how one factor affects another, it is necessary for a decision-maker to set up a threshold value to filter out some negligible effects. In doing so, only the effects greater than the threshold value would be chosen and shown in a figure. In this study, the threshold value is set up by computing the average of the elements in matrix T. The digraph can be acquired by mapping the dataset of (r + c, r − c) (Shieh, Wu, and Huang 2010).

The threshold value is calculated as 0.1826.

A causal diagram is drawn by mapping the values of (R_ij+C_ij, R_ij−C_ij), where the horizontal axis refers to the values of (R_ij+C_ij) while the vertical axis refers to the values of (R_ij−C_ij) (Si et al. 2018) (see Table 9).

Step 6:

Step 6 (ri + cj) shows the total effects given and received by factor i. (ri + cj) indicates the degree of importance that factor i plays in the entire system. On the contrary, the difference (ri − cj) depicts the net effect that factor i contributes to the system. Specifically, if (ri − cj) is positive, factor i is a net cause, while factor i is a net receiver or result if (ri − cj) is negative (Table 10).

While R is the amount of influencing and C is the amount of impactability of each factor, R+C demonstrates the accumulation of effectiveness and impactability of individual deterrence factors, and R-C is the net amount of effectiveness (influentiality). To this end, the biggest amount of R+C is devoted to asymmetric ways of war which has the most powerful network among the factors and in Figure 1 is located in the far right of the horizontal axis. Similarly, the largest amount for R-C is associated with Shia religion, which is at the top of the vertical axis.

Figure 1. Illustration of the causal relations among the factors.

Results and Discussion

The results presented in Tables 3 and 10, and Figure 1 provide a response to the two main research questions guiding this study. SLR and Delphi techniques demonstrate thirteen factors preventing Iran from adopting a nuclear deterrence policy and DEMATEL unveils the influence rate of individual factors on Iran’s deterrence policy and shows the causal relation between these factors. The analysis reveals that these factors mutually influence one another. Nevertheless, it is observed that six factors exert greater influence than being influenced, while seven factors are more susceptible to being impacted than being influential.

Table 10. Calculation of R+C and R-C.

Factors	R	C	R+C	R-C
Shia religion	3.438	0.6198	4.0577	2.8182
International security environment	3.0161	2.5728	5.5889	0.4433
The ideology of the leaders	3.0022	1.4939	4.496	1.5083
Strategic culture of Iran	2.7509	2.4788	5.2297	0.2721
International pressures	2.7418	2.3383	5.0801	0.4034
Asymmetrical deterrence capabilities	2.5762	3.4331	6.0094	−0.8569
International organizations	2.4514	1.8046	4.256	0.6467
Diplomacy and international agreements	2.4081	3.4371	5.8452	−1.029
Iran’s logic to prevent the formation of a nuclear competition	2.0668	2.6909	4.7577	−0.6241
Cost-benefit considerations	2.0534	3.5101	5.5635	−1.4567
Cognitive decision-making process	1.9369	2.5106	4.4475	−0.5737
Lack of financial resources	1.332	1.9172	3.2492	−0.5852
Scientific weakness	1.0864	2.0529	3.1393	−0.9665

According to my research’s findings that are based on the perception of experts, the Shia religion with an influence rate (R-C) of 2.8182 is widely regarded as the primary influential factor inhibiting Iran’s adoption of a nuclear deterrence strategy. The religious factor not only shapes the direction of Iran’s deterrence policy but also significantly impacts nine out of thirteen driving factors behind said policy. Among all factors influencing Iran’s deterrence policy, only international organizations, lack of financial resources, and scientific weaknesses are not influenced by Shia religion.

While rationality is an essential criterion for evaluating a country’s security policy, it is not sufficient on its own. Military behavior cannot be comprehensively understood solely within rational terms, as cultural factors also come into play, such as the influence of the Shia religion in Iran. Thus, if the Shia religion did not form the foundation of Iran’s way of life, there would likely be different interpretations of concepts such as enemy and friend, as well as conventional defense and deterrence strategies.

The ideology of Iranian leaders, particularly Ayatollah Khamenei, Iran’s Commander in Chief of all military forces, with an R-C of 1.5083, holds great significance in determining potential military approaches to deter aggression against the country. Ayatollah Khamenei has consistently emphasized that the possession, development, and use of nuclear weapons are religiously prohibited within Shia doctrine. This specific ideology of Ayatollah Khamenei is one of the primary factors preventing the adoption of a nuclear deterrence strategy by Iran. This finding aligns with the results of my analysis, which affirms the influential role of the ideology of leaders influenced by the Shia religion, impacting nine other factors, albeit to a lesser degree than the Shia religion itself. Consequently, it is ranked as the second most influential factor hindering Iran’s adoption of a nuclear deterrence strategy.

Excluding the “role of Shia jurisprudence” and the “ideology of leaders” from the equation would yield different and inaccurate outcomes. Without these two factors, Iran could have maintained its status as a key ally of the United States in West Asia, eliminating any room for hostility with the United States and Israel. Presently, Iran possesses the potential capability to enrich to levels above 90%. Without the religious and ideological constraints, Iran could have developed its own nuclear deterrence capabilities, similar to neighboring Pakistan. Hence, I assert that the role of the Shia religion in Iran’s military behavior holds great importance and should not be underestimated. The findings of the current study, therefore, prove the arguments of Taremi (2005), Nowrouzani (2009), Guzansky and Golov (2015), and Eslami and Vieira (2022). Figure 2 visually demonstrates the causal relationship between the Shia religion and the ideology of leaders and the various other factors impeding Iran from embracing a nuclear deterrence policy.

Figure 2. The influence of Shia religion and ideology of leaders on other factors.

In contrast to the aforementioned domestic factors, the subsequent trio of factors impeding Iran from adopting a nuclear deterrence strategy are of an international nature. International organizations and institutions such as the United Nations and International Atomic Energy Agency with an R-C of 0.6467, alongside international pressures like economic sanctions and political isolations with an R-C of 0.4034, as well as the international security environment with an R-C of 0.4433, exert influence on Iran’s deterrence policy and preclude the adoption of a nuclear deterrence strategy. Although these three factors have a relatively equal impact on Iran’s deterrence policy, their overall influence remains modest.

Based on the outcome of this analysis, Iran’s abstaining from nuclear warheads may be attributed more to internal factors such as the Shia religion and the ideological stance of its leaders rather than the imposition of comprehensive sanctions or the oversight of international organizations. Accordingly, the means for managing Iran’s nuclear ambitions should be examined within the framework of the Shia religion and the ideological orientation of its leaders. To this end, the present study disproves the research findings of Sagan et al. (2007), Parasiliti (2009), Dobbins (2011), and Drezner (2022). It is worth noting that, despite the relatively low level of influence of these three factors (international organizations, international pressures, and international security environment), they are interconnected with a growing number of factors and are subject to influence from a significant array of them. Consequently, their significance in shaping Iran’s deterrence policy persists.

Iran’s strategic culture with an R-C of 0.2721 is a significant determinant in the country’s reluctance to adopt a nuclear deterrence strategy. Strategic culture is deeply rooted in historical experiences such as the Iran-Iraq war, the geographical location of Iran in an unstable region, diverse ethnicities and languages that contribute to the national identity, and the tenets of the Shia religion. Deterrence, alongside self-sufficiency and a distrust of global powers, is a crucial principle within Iran’s strategic culture. Viewing strategic culture as a set of norms and beliefs regarding the use of force, it is evident that strategic culture plays a vital role in shaping Iran’s approach to deterrence. This analysis reveals that Iran’s strategic culture both influences and is influenced by a range of factors, with seven factors found to prevent the country from adopting a nuclear deterrence strategy, which is in line with the research of Cain (2002), Knepper (2008), and Gerami (2018), and proves their arguments.

The next seven factors preventing Iran from adopting a nuclear deterrence strategy have a low R-C and high R+C (impactability). Scientific weaknesses with a R-C of −0.9665 and R+C of 3.1393 and lack of financial resources with a R-C of −0.5852 and R+C of 3.2492 are good instances for this claim. As an isolated country, Iran is in hardship to access the scientific achievements of different countries in the field of nuclear sciences. Accordingly, most of Iran’s nuclear progress including the development of advanced centrifuges and increasing the enrichment level has been made by trial and error, which is time consuming, dangerous, and expensive. Moreover, Iran has problems with securing the national budget due to international sanctions. This financial problem limits Iran’s investment in its nuclear program.

Iran’s cognitive decision-making process with a R-C of −0.5737 and R+C of 4.4475 and its logic to prevent the formation of nuclear competition in the region with a R-C of −0.6241 and R+C of 4.7577 as well as cost and benefit calculations with a R-C of −1.4567 and R+C of 5.5635 are three other factors preventing Iran from adopting a nuclear deterrence strategy. They are influenced by an increased number of factors, especially Shia religion, international security environment, international organizations, and Iran’s strategic culture. Accordingly, the benefits of adopting a nuclear deterrence strategy are considered to be less than its costs for Iran as a Shia regime that is located in an insecure region.

Diplomacy and international agreements with a R-C of −1.029 and R+C of 5.8452, such as the NPT and the JCPOA, are also among factors affecting Iran’s nuclear policy and deterring the country from pursuing a nuclear deterrence strategy. While the prevailing viewpoint among Western scholars, such as Sagan et al. (2007), Parasiliti (2009), Dobbins (2011), Kroenig (2018), Maher (2020), Arena (2021) and Drezner (2022), emphasizes the significance of diplomatic engagement and international cooperation in averting Iran’s development of nuclear warheads, the analysis indicates that the impact of diplomacy on Iran’s deterrence policy is relatively limited. This finding supports the notion that Iran has shown reluctance to negotiate over its defense capabilities.

Furthermore, asymmetric deterrence capabilities with a R-C of −0.8569 and R+C of 6.0094 assume a significant role in deterring Iran from embracing a nuclear deterrence strategy (see figure 3). Essentially, by relying on asymmetric methods of warfare, Iran perceives no necessity in developing a nuclear deterrence strategy. In this vein, this research proves Olson (2016), Freedman (2017), Ajili and Rouhi (2019), Ahmadian and Mohseni (2019, 2021), Eslami and Vieira (2020, 2022), Akbarzadeh et al. (2023) and all contributions pointing at a close connection between Iran’s deterrence strategy and its asymmetric ways of war and forward defense doctrine. This analysis demonstrates that the influence of asymmetric deterrence capabilities is intertwined with various factors, rendering it the most intricate causal relationship network with other factors. Consequently, asymmetric ways of war are seen as viable alternatives to a nuclear deterrence strategy. This approach enables Iran to safeguard the country’s interests while upholding the tenets of Shia religion and the leaders’ ideological principles. Moreover, in the sphere of international security, asymmetric deterrence capabilities are more widely accepted and less subject to criticism than a nuclear deterrence strategy due to its adherence to international treaties and agreements and absence of sanctions. Ultimately, asymmetric deterrence capabilities help prevent the emergence of nuclear competition in the region and aligns with the cost and benefit calculations of the Islamic Republic of Iran.

Figure 3. The causal relation network of asymmetric deterrence capabilities.

Conclusion

Following the 2003 US invasion of Iraq, Iran’s official and semi-official documents have placed significant emphasis on the notion of “deterrence” (bazdarandegi). The advancement of Iran’s ballistic missile program, coupled with its increasing capabilities in uranium enrichment, increases the perception that Iran is actively pursuing the development of nuclear weapons. In 2021, Iran’s Atomic Energy Organization (sazmane energie atomi) declared that the country was capable of enriching uranium up to the level of 90%. Iranian leadership consistently asserts, however, that the ballistic missile program serves as a substitute for nuclear weapons rather than a means of delivering nuclear warheads. In this vein, Iran’s deterrence approach remained non-nuclear, centered primarily on the insecurity of its borders and the threat of the United States and Israel, without being supplanted by a deterrence strategy with nuclear weapons as its cornerstone.

Aiming to identify the factors inhibiting Iran’s development of a nuclear deterrence strategy and to ascertain the causal relations among these factors, this study employed a novel analytical approach integrating SLR, Delphi, and DEMATEL techniques. The findings of this analysis revealed a comprehensive inventory of thirteen internal and international factors influencing Iran’s deterrence strategy (Table 4). Notably, these factors not only impact Iran’s deterrence policy but also exhibit interconnected causal relationships, collectively impeding Iran’s pursuit of nuclear bombs. An in-depth examination of the thirteen factors obstructing Iran’s advancement in nuclear military capabilities reveals that ten of these factors possess broader applicability beyond Iran and are pertinent to other nations. Elements such as international organizations, diplomacy, international security environment, international economic pressure, lack of financial resources, scientific weaknesses, cost-benefit calculations, cognitive decision-making processes, and logic/aspiration to prevent nuclear competition are germane to other countries as well. Hence, it prompts the inquiry as to why Pakistan, a Muslim nation situated in a comparable “geography of threat”, opted for nuclear deterrence while Iran did not. Addressing this query necessitates an exploration of factors exclusive to Iran and its distinct governance framework.

This analysis underscores the paramount influence of Shia religious beliefs and the ideological stance of Iranian leaders in obstructing the adoption of a nuclear deterrence strategy by Iran. Moreover, the centrality of Shia religion in shaping the ideological orientation of Iranian leadership underscores the unique role of these two distinctive factors within the Iranian political framework, steering Iran towards eschewing nuclear deterrence strategies in favor of asymmetric ways of war. Consequently, the religious prohibition within Shia doctrine against the possession of weapons of mass destruction stands as the primary impetus driving Iran’s significant investments in ballistic missile programs. Leveraging Shia religious tenets, Ayatollah Khamenei, in his capacity as the Valie Faghih, regards ballistic missiles not as a delivery mechanism for nuclear warheads, but as a viable substitute for nuclear armaments. The delegation of the deterrence mission to ballistic missiles has led to the development of one of the largest and most diverse ballistic missiles arsenal by Iran.

This study presents a policy recommendation for world leaders who have sought to deter Iran from acquiring nuclear capabilities through regime change initiatives. Taking into consideration the implications that altering the regime in Iran may yield unintended consequences for its nuclear program, the most feasible approach to influence Iran’s nuclear pursuits appears to be through diplomatic engagement and negotiation with the existing leadership of the Islamic Republic of Iran that is not interested in the development of nuclear bombs due to Shia religious constraints.

In conclusion, this study lays the foundation for two potential avenues of future research. Firstly, an exploration of the influence of domestic factors, including religion, leadership ideologies, and strategic culture on the deterrence policies of distinct nuclear nations could be pursued using a systematic research framework akin to the one employed in this study. Secondly, the methodological approach introduced in this study can be used to scrutinize and elucidate the underlying motivations driving the nuclear ambitions of individual countries.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the This study was conducted at the Research Centre in Political Science (uIDB/CPO/00758/2020), university of Minho/university of Évora, and supported by the Portuguese Foundation for Science and Technology (FCT) and the Portuguese Ministry of Education and S [uIDB/CPO/00758/2020].

Notes on contributors

Mohammad Eslami

Mohammad Eslami is an Assistant Professor of International Relations at the University of Minho in Portugal and an Integrated Member of the Research Center for Political Science (CICP). He was also a research fellow at the Arms Control Negotiation Academy of the Davis Center for Russian and Eurasian Studies at Harvard University. His research interests primarily relate to International Security, Arms control, Nuclear Proliferation, and Middle East Studies. He has published in International Affairs, Third World Quarterly, Journal for Peace and Nuclear Disarmament, Journal of Asian Security, Small Wars and Insurgencies and Spanish Journal of Political Science and wrote book chapters to several edited volumes published by Springer and Palgrave Macmillan, among others. Mohammad’s most recent book The Arms Race in the Middle East, was published by Springer in 2023.

Notes

¹ I would like to express my deep gratitude to Program-specific Associate Professor Hibiki Yamaguchi, the Journal’s editor, as well as Professor Alena Vieira and the two anonymous reviewers. Their insightful comments played a crucial role in enhancing the quality of this manuscript.

² The genesis of deterrence theorizing can be traced back to the imperative to address the advent of the atomic bomb. Subsequently, a second wave emerged during the 1950s and 1960s wherein game theory was incorporated to shape the prevailing understanding of nuclear strategy (Knopf 2009; Nye 2020; Ven Bruusgaard 2016). The third wave, which materialized in the 1970s, used statistical and case-study methods to empirically test deterrence theory, predominantly in relation to instances of conventional deterrence. This investigation draws on the advancements made by the third generation of deterrence studies (Knopf 2010; Lupovici 2016; Williams 2021).

Appendix 1.

SLR of Iran nuclear deterrence strategy

Table

c	Author(s) and publication year	Journal	Factors preventing Iran from adopting nuclear deterrence strategy
1	Sagan et al. (2007)	Journal of International Affairs	International Organizations International agreements
2	Nowrouzani (2009)	Military Sciences (Persian)	Diplomacy and international agreements- Shia religion
3	Parasiliti (2009)	Survival	International organization International agreements
4	Dobbins (2011)	Survival	Shia religion International pressures including sanctions
5	Edelman et al. (2011)	Foreign Affairs	Diplomacy and international agreements- Economic sanctions-International organizations
5	Waltz (2012)	Foreign Affairs	Diplomacy and international agreements- Economic sanctions-International organizations
7	Dolatabadi (2013)	Defense Policy (Persian)	Iran’s asymmetrical method of warfare- Shia religion-Cognitive decision-making process- The ideology of the leaders
8	Chubin (2014)	Survival	No need for nuclear deterrence Relying on conventional deterrence
9	Barzegar (2014)	International Spectator	International security environment- International agreements- Religion
10	Ghanbari Jahromi (2015)	Defence Studies (Persian)	International Organizations-International agreements-Shia Religion-International pressures including sanctions-Asymmetrical method of warfare- Ideology of the leaders
11	Guzansky and Golov (2015)	Comparative Strategy	International security environment-Cost-benefit considerations-Strategic culture of Iran-Shia Religion-Cognitive decision-making process- The ideology of the leaders
12	Aminian and Zamiri-Jirsarai (2016)	Security Horizons (Persian)	Iran’s asymmetrical method of warfare- International security environment-Cost-benefit considerations-International Organizations
13	Freedman (2017)	Comparative Strategy	Iran’s asymmetrical method of warfare- International sanctions- Cost and benefit calculations- Financial threats
14	Ahmadian and Mohseni (2019)	International Affairs	Relying on conventional deterrence via BMP Asymmetrical deterrence capabilities Drawing on costs and benefits calculations
15	Maher (2020)	Review of Economics and Political Science	International agreements (NPT-JCPOA)
16	Ansari Fard and Haji-Yousefi (2023)	Geopolitics Quarterly	Relying on conventional deterrence via BMP Asymmetrical deterrence capabilities

Appendix 2.

Iran nuclear deterrence factors based on their frequency in papers (SLR)

Table

#	Factor	Frequency
1	Diplomacy and international agreements (NPT-JCPOA)	5
2	Cost-benefit considerations	4
3	Economic sanctions and financial threats	4
4	International Organizations	3
5	International pressures including sanctions	2
6	Asymmetrical deterrence capabilities and method of warfare	2
7	Relying on conventional deterrence (via BMP)	2
8	Shia religion	2
9	Cognitive decision-making process	1
10	Ideology of the leaders	1
11	International security environment	1
12	No need to nuclear deterrence	1
13	Strategic culture of Iran	1

Appendix 3.

Delphi primary questionnaire

Table

#	Questions	Very low	low	Moderate	High	Very High
1	To what extent the “diplomacy and international agreements (NPT-JCPOA)” impacts the deterrence of Iran from approaching to nuclear weapons?
2	To what extent the “cost-benefit considerations” impacts the deterrence of Iran from approaching to nuclear weapons?
3	To what extent the “economic sanctions and financial threats” impacts the deterrence of Iran from approaching to nuclear weapons?
4	To what extent the “International Organizations” impacts the deterrence of Iran from approaching to nuclear weapons?
5	To what extent the “International pressures including sanctions” impacts the deterrence of Iran from approaching to nuclear weapons?
6	To what extent the “Asymmetrical deterrence capabilities and method of warfare of Iran” impacts the deterrence of Iran from approaching to nuclear weapons?
7	To what extent the “Relying on conventional deterrence (via BMP)” impacts the deterrence of Iran from approaching to nuclear weapons?
8	To what extent the “Shia religion” impacts the deterrence of Iran from approaching to nuclear weapons?
9	To what extent the “Cognitive decision-making process” impacts the deterrence of Iran from approaching to nuclear weapons?
10	To what extent the “Ideology of the leaders” impacts the deterrence of Iran from approaching to nuclear weapons?
11	To what extent the “International security environment” impacts the deterrence of Iran from approaching to nuclear weapons?
12	To what extent the “No need to nuclear deterrence” impacts the deterrence of Iran from approaching to nuclear weapons?
13	To what extent the “Strategic culture of Iran” impacts the deterrence of Iran from approaching to nuclear weapons?

Open Question

In your mind, what are other factors that has any impact on the deterrence of Iran from approaching to nuclear weapons?

Appendix 4.

DEMATEL questionnaire

Table

	Diplomacy and international agreements	Cost-benefit considerations	International pressures	International organizations	Strategic culture of Iran	Asymmetrical deterrence capabilities	Shia religion	Cognitive DM process	Ideology of the leaders	International security environment	Lack of financial resources	Scientific weakness	Iran’s logic to prevent formation of a nuclear competition in the region
Diplomacy and international agreements	0
Cost-benefitconsiderations		0
International pressures			0
International organizations				0
Strategic culture of Iran					0
Asymmetrical deterrence capabilities						0
Shia religion							0
Cognitive DM process								0
Ideology of the leaders									0
International security environment										0
Lack of financial resources											0
Scientific weakness												0
Iran’s logic to prevent formation of a nuclearcompetition in the region													0

The first column presents the factors preventing Iran from adopting a nuclear deterrence policy. Please demonstrate the impact of individual factors on the other factors by grading them from Zero (non-influential) to 5 (very influential). Please note that the impact of each factor on itself is considered to be Zero.