Strategic Assessment

Introduction

Iran is a country with a unique security concept, whose primary goals are to ensure the regime's stability, achieve regional hegemony, and export the Islamic Revolution. This concept stems from several fundamental elements: Iran's long history; its radical religious beliefs, which determine regime policy; the ambitions of the regime, which leads the Shiite Muslim camp; Iran's geographic location, which helps its effort to expand its influence in the surrounding area; and the powerful enemies that it faces. These elements require the regime to anticipate and confront many threats, while at the same time, its policy poses threats to regimes and organizations in the region (Kam, 2004).

This article analyzes Iran's deterrence concept and its singular importance to the Iranian regime. In his monumental book War and Strategy, Yehoshafat Harkabi explains that underlining the deterrence concept is an explicit or implicit threat by one of the sides to attack its adversary severely if the latter takes a hostile step against it. The deterrent threat will be effective if the adversary believes that the side threatening it has the tools, capability, and determination to carry out its threat (Harkabi, 1990). There are also states of mutual deterrence, meaning that each of the sides has the ability to hurt the other. In such a situation, it is possible that both sides will refrain from attacking one another out of concern that an attempt to attack the adversary will lead to severe reciprocal harm.

This article will assess the goals of Iran’s deterrence against the regime’s external enemies and adversaries, now headed by the United States and Israel; analyze the tools used by Iran for deterrence purposes—usually military tools, primarily the large arsenal of missiles possessed by Iran and its proxies; examine a future concept of nuclear deterrence in the event that Iran attains nuclear weapons; study the deterrence resulting from Iran's partial control of the Gulf and its ability to utilize Shiite militias and terrorism; and finally, address the strengths and weaknesses of Iran's deterrence concept. The main conclusion is that Tehran’s tools can deter Iran's adversaries, including even the United States and Israel. The Iranian deterrence concept, however, also has weak points that can deter Iran as well from acting against its adversaries. The article does not address deterrence of internal adversaries, because this is usually based on political tools, has different goals, and is not part of military deterrence. This concept, therefore, requires a different analysis.

Iran’s Threat Perception

Deterrence is the foundation of Iran's security concept, which to a large extent has been shaped by security problems of recent decades. First, Iran's main adversaries were, or are, major powers: Czarist Russia and the Soviet Union were the primary threat to Iran until the collapse of the Communist regime; the United States became the main threat to Iran after the Iranian regime severed the bilateral ties following the Islamic Revolution, and after the United States intervened with military force in the Middle East in the two Gulf Wars. The second tier of Iran's adversaries at various times in history has consisted of regional powers to the west of Iran. The most relevant of these in the preceding generation was Iraq under Saddam Hussein, which forced Iran into the Iraq-Iran War—the longest Middle East war in recent times—and greatly influenced Iran's concept of security and deterrence. Iran also regards Israel as a regional military power that in cooperation with the United States strives to undermine Iran's regional status. On another level, Iran also struggles with various terrorist organizations operating inside the country and around it, headed by ISIS. Iran's deterrence concept is first and foremost aimed against all of these adversaries.

Iran's situation has meanwhile improved in two aspects. Since the dissolution of the Soviet Union, Iran no longer regards Russia as a significant threat, and Russia is even aiding Iran. Since the Gulf Wars, Iraq has lost most of its military capabilities and is no longer able to threaten Iran. 

The United States, however, has arisen as a power posing a threat to Iran. In certain ways, the United States is more dangerous to Iran than the Soviet Union was previously: in the two Gulf Wars, the United States took control of Afghanistan and Iraq, Iran's eastern and western neighbors. The United States has allies and partners in the region, and maintains considerable military forces close to Iran. It has shown willingness to use military force against Iran when necessary, and the Iranian regime believes that the United States is planning to overthrow it. The United States likewise has the ability to exert heavy economic pressure on Iran, and is currently doing so.

Second, Iran overall has no real nation-state allies that can help it deter its adversaries. The only ally that stood at its side was Syria, under the regimes of Hafez al-Assad and his son, Bashar al-Assad. Since the beginning of the Arab Spring, however, Syria's ability to help Iran against its adversaries has declined sharply. Iranian entrenchment in Syria is very important to the Iranian regime, because the establishment of military outposts in Syria helps Iran enhance its power of deterrence, Hezbollah capabilities, and the threat to Israel. Since 2013, however, Syria has become an economic burden on Iran, and this in turn sparks opposition among various groups in Iran. Syria's military power was damaged severely in the civil war, and Syria is in need of large-scale Iranian military and economic aid. Iran receives no material external aid against the American threat: Russia cooperates with Iran in the military, economic, and nuclear spheres, but it has given Iran no help in dealing with the Israeli attacks against Iranian and Shiite targets in Syria. Russia also competes with Iran for the leading role in rebuilding Syria, and for influence in the country.

Third, Iran lags behind its main rivals in conventional weaponry, especially in airpower. The Iranian air force still comprises relatively outmoded aircraft produced by the United States, Russia, and China, or self-produced, and is incapable of countering the American and Israeli air forces in the current situation. For this reason, it has never been deployed in the Syrian theater against the attacks conducted by Israel. The Iranian air defense has also failed to show much effectiveness against the Israeli attacks in Syria.

Iran’s Deterrence Goals

The threats perceived by Iran lead it to understand that despite its assets and capabilities, it faces powerful rivals and enemies, some of which are stronger than Iran, headed by the major powers. This was not an inevitable development. During the Shah's regime, Iran was an ally of the United States and had close relations with Israel. Only under the Islamic regime did Iran sever its relations with the United States and Israel, and it is consciously paying the price of its hostility.

Coping with militarily and technologically powerful countries thus requires Iran to build capabilities that will not only provide it with sound defense, but also deter its enemies from initiating an attack against it, whether such an attack is of large or limited scope.

Iran's deterrence concept takes into account the United States’ military and technological superiority and the need for an appropriate response to this advantage. As conceived by the Iranian regime, this response rests on the concept of asymmetric warfare, adopted in face of its inferiority to its strong adversaries. On the one hand, this concept requires Iran to detect and exploit the military and technological weak points of the strong adversary, so that inferiority will not cause its defeat when put to the test. On the other hand, Iran strives to maximize its capabilities and advantages in surprising and unconventional fashion, even when it is the weaker of the two sides, by developing relatively simple but deadly weapons, attacking its enemy's weak points in unexpected ways, using unconventional tactics, and neutralizing its enemy's strong points (Pinko, 2017).

Coping with militarily and technologically powerful countries thus requires Iran to build capabilities that will not only provide it with sound defense, but also deter its enemies from initiating an attack against it, whether such an attack is of large or limited scope. Concretely, Iran's goal is to deter the United States and Israel from taking several actions:

1. Military action by the United States against Iranian targets and Shiite militia targets, mostly in Iraq and Syria, and if the situation deteriorates, perhaps against the Iranian missile system as well. These targets are also likely to include the Iranian nuclear sites. Iran is likewise trying to deter the United States from continuing, let alone escalating, the economic sanctions against it, and from aiding Iranian opposition groups.
2. Air attacks by Israel against Revolutionary Guards and al-Quds targets and Shiite militia targets outside Iran. Iran also seeks to deter Israel from attacking missile arsenals controlled by the Iranians and their proxies in Iraq, Syria, and Yemen, and in an extreme situation, in Lebanon as well, and perhaps in Iran itself. Above all, Iran will strive to deter Israel from attacking the nuclear sites in Iran, possibly with American backing, and from Israeli efforts to sabotage these sites.
3. Cooperation by the Gulf states, headed by Saudi Arabia, with the United States and possibly with Israel against Iran, from measures that will assist the presence and activity of the United States in the Gulf region.

The Iranian Deterrent Toolbox

Iran's concept of deterrence is partly based on the state’s core characteristics. In Middle East terms, Iran is a large country, both in terms of territory and population. Its mountainous terrain provides it with natural defense, and makes it difficult to invade. Iran controls the entire eastern shore of the Persian Gulf, from the Iraqi border to the Pakistani border. This control enables it to influence shipping and oil exports in the Gulf, and to find ways to deter enemies that are active there. With the second largest population in the Middle East, Iran is able to recruit enough manpower for its large military, while oil revenues help it develop diverse weapon systems and build an advanced nuclear program. It is also the world's largest Shiite country. These features enable Iran’s intervention in other countries in the region and its influence over their policies and actions.

Two developments have had a major effect on Iran's deterrence concept. One was the Islamic Revolution, which fundamentally changed the nature of the regime and led it to redefine its enemies—headed by the United States and Israel—and the ways of dealing with them. The second development was the Iraq-Iran War, which made clear to Iran the failure of its deterrence against Iraq—Iraq took Iran by surprise early in the war, and used its large arsenal of missiles and chemical weapons—and the need to build diverse deterrence tools to help it cope with its new enemies.

The Missile System

The most important deterrence tool developed by Iran is its missile system, which now includes various missiles with a range of up to 2,000 kilometers. Iran, however, is apparently seeking to extend this range. Upon the outbreak of war with Iraq in September 1980, Iran had no ballistic missiles beyond short-range rockets, while Iraq had a large arsenal of Scud missiles acquired from the Soviet Union. Furthermore, Iraq surprised Iran during the war with massive missile barrages fired at Iranian cities. Iran quickly purchased missiles from all available sources—primarily from North Korea, Syria, and Libya—and responded in 1988 with its own missile barrages against Iraqi cities as part of what became known as the "War of the Cities." Iraq, however, had a clear advantage in missiles, which made an important contribution to Iran's decision in the summer of 1988 to agree to end the war on what to it were unfavorable terms, including leaving Iraqi forces on Iranian territory even after the end of the war.

Iran learned its lesson. The Iranians were impressed by the Iraqi missile system's ability to strike at civilian targets, and the resulting dire effect on the morale of the Iranian population. At the same time, the Iranian air force and its outmoded aircraft were unable to cope with the air forces of the United States and Israel. Iran's missile system thus became its main deterrence tool against its principal adversaries—the United States, Israel, Saudi Arabia, and the terrorist organizations operating against Iran, headed by ISIS. As of now, Iran has no missiles capable of striking the Western hemisphere, and it will take years before it can manufacture long-range missiles. American sources suspect, however, that it intends to do so. Meanwhile, Iran has signaled that it is able to attack American bases in the Middle East and United States allies, even in the current situation.

The most important deterrence tool developed by Iran is its missile system, which now includes various missiles with a range of up to 2,000 kilometers. Iran, however, is apparently seeking to extend this range.

Iran is enhancing this arsenal with four important characteristics. The first is diversity: in addition to ballistic missiles, it includes other missiles of various types, among them cruise missiles, coast-to-sea missiles that enhance Iran's ability to attack ships in the Gulf and disrupt shipping there, and unmanned aerial vehicles (UAVs) of the type it used to attack Saudi oil facilities in September 2019. The second is an ongoing effort to improve the accuracy of its missiles for the purpose of conducting precision strikes against strategic and military targets. The third is the missile arsenals that Iran is building for the Shiite militias under its command. These include first and foremost Hezbollah's large arsenal of missiles, the rocket and the missile arsenals of the Iraqi Shiite militias linked to Iran, and the arsenal of the Houthi rebels in Yemen. The fourth, which Iran naturally does not mention, is Iran's nuclear program. If and when Iran obtains nuclear weapons, the deterrent ability of its missiles, which will constitute the main platform for launching nuclear weapons, will be strengthened.

Iran has an advantage in missiles over most of its rivals in the Middle East, which regard the arsenal as a key threat. The deterrence of Iran's missiles is dynamic and changes over time, and will become stronger as their precision improves. For distant countries, such as in Western Europe, the force of the deterrent will also increase when the missile range is extended. On the other hand, the force of the deterrent can also decline, for example, when the threatened country is able to develop or acquire effective anti-missile defense systems. Israel's successful development of several anti-missile defense layers—the ability to take successful action against the rockets and missiles possessed by Iran, Hezbollah, and Hamas—has reduced these enemies' deterrent power.

The Iranian missile arsenal is naturally a strong deterrent against militarily inferior adversaries, such as Saudi Arabia, but it also has a deterring effect against countries with greater military power, above all the United States: even if the United States has a clear and substantial military advantage over Iran, the US administration is liable to be deterred from a conflict, whether because it wishes to avoid involvement in a large-scale conflict in the Middle East, or because Iran can hurt US interests at sensitive points—for example, United States allies or freedom of navigation in the Gulf.

Iran has thus far used its missile system against its enemies only a few times, and even on those occasions fired few missiles. Iran first shot missiles against American targets in Iraq in January 2020, following the killing of al-Quds force commander Qasem Soleimani. In 2017 and 2018, Iran fired missiles against ISIS targets in Syria and against Kurdish rebel targets in northern Iraq. It also fired 20 rockets at IDF forces in the Golan Heights in May 2018, following IDF air strikes against Iranian and Shiite targets in Syria. The small number of cases in which Iran fired missiles against American and Israeli targets indicates that Iran plans to strengthen its deterrent against its adversaries, and signals that it will increase its missile firepower against them in the future. Meanwhile, however, Iran is acting cautiously and with restraint in order to avoid escalation into a large-scale conflict (Zeitoun et al., 2018; Kam, 2019; Rubin, 2018; Eisenstadt, 2017).

Nuclear Deterrence

Iran as yet has no nuclear weapons, and claims to have no plans to develop them. Since 1987, however, Iran has been building an advanced nuclear program, whose main purpose is presumably the development of nuclear weapons. It appears that in the initial stage, Iran sought nuclear weapons as defense against Iraq, which preceded Iran in its efforts to develop nuclear weapons; the prolonged and bloody war with Iraq accelerated Iran’s nuclear drive. After Saddam Hussein lost most of Iraq's military power in the two Gulf Wars, Iran's nuclear program was designed as a response to its two enemies that already had nuclear weapons, the United States and reportedly Israel, and deter them from attacking Iran with nuclear weapons. At the same time, Iran's development of a nuclear capability was designed to enhance its power, status, influence, and presence in the region.

Even if Iran obtains nuclear weapons, and despite the powerful threat that these weapons pose, they will not necessarily constitute Iran's main deterrent tool. Despite the severity of the nuclear threat, the risk that Iran will use these weapons against Israel or other countries does not appear high at present, for several reasons. According to foreign sources, Israel has a substantive arsenal of nuclear weapons, and there is no precedent of a country with nuclear weapons using them against another nuclear-armed country. If Iran believes that Israel has second-strike capability, it is difficult to believe that it will run the risk of Israel launching nuclear weapons against Iranian cities, which would kill hundreds of thousands of Iranians. Furthermore, it is clear to Iran that all US administrations have been committed to Israel's existence and security, and the regime must assume that a nuclear attack against Israel will result in an overwhelming American response against Iran. It is even less likely that Iran will attack the United States itself or other American allies, such as Saudi Arabia, with nuclear weapons (Kam, 2007).

Even if Iran obtains nuclear weapons, and despite the powerful threat that these weapons pose, they will not necessarily constitute Iran's main deterrent tool. Despite the severity of the nuclear threat, the risk that Iran will use these weapons against Israel or other countries does not appear high at present.

It therefore follows that even if Iran obtains nuclear weapons, it will reserve them for use in extreme situations, if at all. In most situations, Iran's main deterrent tool is likely to remain its current tool—its large missile arsenal. This is also true of Israel's ability to deter its enemies, including Iran. Egypt and Syria went to war against Israel in 1973 believing that Israel possessed nuclear weapons at the time, on the assumption that Israel would not use nuclear weapons against them. It is likely that Iran now believes that Israel's deterrent tool against the Iranian missile system includes advantages such as an excellent air force, superb intelligence, an anti-missile defense system, and the ability to strike targets accurately at long ranges. At the same time, it appears that Israel’s nuclear capability has not hitherto been regarded by Iran as relevant and threatening in the states of tension that have developed between the two countries.

Aerial Deterrence

In the current situation, the Iranian air force is apparently not an important deterrent factor in Iran's concept regarding the Syrian theater, probably because superior air forces, such as those of the US and Israel, are active in the region. At the same time, in early 2016, Iran negotiated with Russia for a major arms deal that included, inter alia, Sukhoi-30 warplanes and S-400 air defense systems (Kam, 2016). As far as is known, this deal has not yet been signed, but if and when Iran obtains these weapon systems, they will likely become an important deterrent factor in the Iranian concept.

Meanwhile, Iran is expanding the range and strike capability of its armed UAVs for conducting long range air attacks in combination with missiles. The most prominent example is the Iranian attack on the oil facilities in Saudi Arabia in September 2019, in which the US administration alleged that Iran launched a dozen cruise missiles and 20 UAVs at these facilities (Reuters, 2019). Iran therefore demonstrated that it was not deterred from attacking important oil facilities and disrupting shipping in the Gulf. The impressive use of a combination of UAVs and cruise missiles and the severe damage caused to the oil facilities—with no Saudi or American response—likely contributed to Iran's deterrent capability.

Deterrence in the Gulf

In the naval sphere, the Iranian concept of deterrence focuses primarily on the Gulf region, although the Iranian fleet sometimes operates outside this theater as well. Iran's control of the eastern shore of the Gulf affords it the ability to act, attack, and exert considerable influence throughout the entire Persian Gulf, including its bottleneck—the Strait of Hormuz. Furthermore, based on the lessons of the Iraq-Iran War, Iran built a diversified naval capability, which includes regular and midget submarines, missile boats, small high-speed boats armed with rockets or missiles, shore-to-sea missiles, shore artillery, thousands of naval mines, and commando units from the Revolutionary Guards fleet trained to take control of ships. The location of the theater close to home and the terrain also help Iran—it controls the eastern side of the Strait of Hormuz, and the Gulf shore contains many large and small bays that can conceal fleet units and be used to conduct surprise attacks.

These tools enable Iran to build a significant naval deterrent capability in the Gulf region and the surrounding area, and Iran has expanded this capability in recent years. Since it recognizes that its forces are inferior to those of the United States, however, Iran is careful not to take action that will prompt the US administration to take a severe response, in order to prevent damage and shocks in the global oil market. Iran has threatened several times to blockade the Strait of Hormuz and to use force to prevent shipping in the Gulf, but has never done so because the United States warned that in such an event, it would use force to open the Strait and allow shipping in the Gulf. No less important, closing the Persian Gulf would also detract from Iran's oil exports. As early as the Iraq-Iran War, Iran realized that closing the Strait would damage it as much as it hurts its adversaries.

Terrorist Attacks and the Shiite Militias

Since the Islamic Revolution, Iran has been linked to terrorist attacks, beginning with attacks against regime opponents in Iran and against countries that aided Iraq in the war against Iran. Every year since 1984, the administration has named Iran in an official document as the world's leading perpetrator of terrorist attacks, based on the extent of the attacks carried out by Iran and its proxies, and the fact that some of these attacks are executed on direct order from the regime's leadership and by the entities controlled by it. In addition, cooperation has sometimes been revealed between Iranian security agencies and non-Iranian terrorist organizations, such as al-Qaeda. Yet while terrorism is an important deterrence tool for Iran, it is also a double-edged sword: since the appearance of al-Qaeda and ISIS, many countries, headed by the major powers, have coordinated joint campaigns against terrorist attacks. Iran will find it difficult to conduct many such attacks without being accused of supporting terrorism.

Iran regards its network of militias as part of its military power and deterrent capability that enables it to present a Shiite bloc with unified military power; intervene militarily in other countries, as with its successful intervention in Syria; and shape the regimes in countries containing a Shiite population.

The idea of Shiite militias is not new to the Iranian leadership. It began to develop in the early 1980s, shortly after the Islamic Revolution, with Iran’s establishment of Hezbollah in Lebanon—the most important and loyal of the militias. In addition to Hezbollah, Iran's network of militias now includes Iraqi Shiite militias loyal to Iran, an Afghan militia, a Pakistani militia, and more recently, a Syrian militia. Iran regards its network of militias as part of its military power and deterrent capability that enables it to present a Shiite bloc with unified military power; intervene militarily in other countries, as with its successful intervention in Syria; and shape the regimes in countries containing a Shiite population. No less important, it enables Iran to avoid losses of its own manpower in warfare, and to maneuver against the internal and external pressures on it resulting from its intervention in Syria and Iraq by placing responsibility for activity in other countries on the militias, while claiming that Iranian army personnel only advise in Syria and do not participate in combat there (Kam, 2017; McInnis, 2017).

Iran's use of militias has at least two implications for its concept of deterrence. The first is that the most important of these militias, Hezbollah and the Iraqi militias, have acquired extensive experience in terrorist attacks and guerilla warfare in Syria, Iraq, and Lebanon. The Houthis have also acquired experience in combat and terrorist attacks in Yemen and in the Arabian Peninsula. In these countries, terrorism and guerilla warfare have been the main form of warfare in the past decade. This experience has given the militias and Iran an important deterrent capability against powerful enemies such as the United States, Israel (where terrorism is an ongoing security problem), and Saudi Arabia. Second, Iran provides large quantities of missiles and rockets to Hezbollah, the Iraqi militias, and the Houthis, as well as to the Palestinian organizations, headed by Hamas and Islamic Jihad. These missile arsenals provide these organizations with considerable power, and constitute an important element in Iran's deterrent capability.

Iran’s Goal to Deter the United States

The Iranian leadership is well aware that the United States enjoys substantial military, technological, and economic superiority over Iran, and that Iran is unable to rebuff American power. Consequently, Iran strives to build military capabilities that will deter and persuade the US administration that despite its military superiority, the United States will pay a heavy price if it attacks Iran. Iran uses several deterrence tools against the United States and its allies in the Middle East for this purpose, and they have contributed to the emergence of a kind of mutual deterrence between the two countries, although this deterrence is not equal on both sides.

The regime likely has no doubt about the ability of the United States to attack Iranian targets in response to Iranian provocations. Iran's doubts concern the administration's readiness and determination to attack Iranian targets, even as Iran threatens that the US will pay a heavy price for attacking Iran. The Iranian belief that the United States will be in no hurry to attack Iran was likely reinforced following Iran’s September 2019 attack on oil facilities in Saudi Arabia, when both the United States and Saudi Arabia refrained from any meaningful response to the attack. On the other hand, the killing of Soleimani by the United States presumably heightened Iran's fear that the Trump administration was liable to respond powerfully to Iranian provocations, reflected in Iran's low-profile response to the painful loss of Soleimani, a key figure in Iran’s upper echelons.

Although Iran fears that the US administration is exerting heavy economic pressure on it in order to create internal unrest in Iran that will lead to the overthrow of its regime, it is doubtful whether it possesses sufficient capability to deter the United States from such actions. The possible Iranian response—a threat against the allies of the United States; a threat to oil exports from the Gulf; enlistment of Russia, China, and European countries to exert their influence with the US administration to reduce its pressure on Iran—is liable to prove insufficient to halt this pressure. 

Iran's main spheres for deterring the United States are the Persian Gulf and Iraq, both on Iran's border, and both with American forces present that constitute a threat to Iran. Iran's strategic goal is therefore to reduce this presence, and to deter the United States from attacking Iranian interests. Given the American strategic advantage, however, Iran is careful to avoid crossing what it perceives as United States red lines, and refrains from actions that could lead to escalation and a large-scale conflict. Among the limited steps that Iran has taken, or is liable to take, against the United States, several are noteworthy.

First, Iran has harassed oil tankers and other vessels in the Gulf—primarily the vessels of the Western and Persian Gulf countries, including sometimes those of the United States. The harassments of recent years were perceived as a response to the renewed sanctions against Iran imposed by the Trump administration, and were designed to emphasize that if Iranian oil exports are harmed, other countries will be harmed as well. Iran, however, never closed the Persian Gulf. Furthermore, even in its harassment of American ships, Iran must avoid crossing any red lines because it fears the American response. In April 2020, then-President Trump ordered the American fleet to destroy any Iranian warship that was harassing the American naval forces, after Revolutionary Guard ships threatened ships of the American fleet in the Persian Gulf (Kube, 2020).

Second, Iran delivers rhetorical threats against its adversaries, led by the United States and Israel, for purposes of deterrence. Iran thereby emphasizes publicly that its large missile system extends to a range of 2,000 kilometers, covering the entire Middle East, including all of the American military targets in the region. Iran's aim of expelling the US forces in Iraq, accompanied by rockets fired by Shiite militias against US army units in Iraq, also contributes to the Iranian deterrent pressure on the United States. Iran likewise threatens to attack American ships that pose a threat to the security of Iranian shipping in the Gulf. Revolutionary Guards commander General Hossein Salami threatened that Iranian ships would open fire on any American ship threatening their security in the Gulf. The commander of the Revolutionary Guards fleet also warned in April 2020 that his fleet possessed sea-to-sea missiles with a range of 700 kilometers. Former Revolutionary Guards fleet commander Admiral Ali Fadavi, now the deputy commander of the Revolutionary Guards, warned in 2014 that in the event of war, Iran would sink American aircraft carriers (Shabad, 2014).

Iran’s Goal to Deter Israel

The Iranian regime regards Israel as a serious threat—second only to the American threat. It therefore believes that it is important to deter Israel from attacking its assets and influence in the Middle East. In recent years, the main conflict between Iran and Israel has taken place in and around the Syrian theater, with the Israeli air force repeatedly attacking targets of the Shiite militias and the Revolutionary Guards. These attacks are aimed at disrupting Iranian entrenchment in Syria and the Iranian effort to create another front against Israel and upgrade Hezbollah's missile arsenal in Lebanon. As of now, Iran has been unable to deter Israel from continuing these attacks, despite the many losses and heavy damage that the attacks have inflicted on the Shiite and Iranian forces.

Iran has the ability to respond by striking targets in Israel in an attempt to deter Israel from continuing these air attacks, mainly by using Hezbollah's store of missiles in Lebanon and Iran's own missiles. However, to date Iran has used missiles in Syria against Israeli targets in only a few cases, and on a limited scale. This is no accident; it reflects Iran's cautious approach aimed at avoiding escalation on a large scale that is liable to culminate in concrete American support for Israel, possibly including an attack on the nuclear sites in Iran.

Thus far, Israel has not conducted air attacks against military targets in Iran, but several explosions and fires have occurred at the Iranian nuclear sites in recent years. One of the most severe of these was the explosion in the uranium enrichment facility in Natanz in April 2021, which Iran attributed to Israel. Most likely Iran believes that in a large-scale conflict, Israel is liable to attack strategic targets in Iran, above all the nuclear targets: Israel has made it clear that it will not allow Iran to obtain nuclear weapons, and Israel has already attacked nuclear sites near Iran, in Iraq and Syria, on two occasions, in order to prevent those countries from obtaining nuclear weapons. Furthermore, in certain situations, particularly if Iran crosses the red line toward nuclear weapons, the US administration might back attacks by Israel on the nuclear sites in Iran in order to avoid a general Middle East escalation resulting from Iran’s achievement of nuclear capability.

Despite Israel's deterrent capability against Iran and Hezbollah, there is mutual deterrence between the two sides, because even before Iran obtains nuclear weapons, it has created its own deterrence against Israel.

Nonetheless, Iran may well produce a nuclear weapon one day. The Iranian nuclear program has existed since 1987, and presumably its ultimate goal is to obtain a nuclear weapon. Until now, Iran has settled for the status of a nuclear threshold state, and the nuclear agreement of 2015 requires Iran to refrain from crossing the nuclear threshold. Since the Trump administration withdrew from the nuclear agreement, however, Iran has also deviated from its obligations under the agreement, and has neared the nuclear threshold. Possession of nuclear weapons by Iran will create a new level of threat and a far graver deterrent against Israel and Saudi Arabia. Israel will regard nuclear weapons in the hands of Iran as an existential threat, because for the first time, an enemy country will have the ability to deal Israel a critical blow, while the Iranian regime's radical ideology will require Israel to take into account the possibility of a nuclear attack against it. The limitations of using these weapons against Israel, however, should be kept in mind. Israel might take action against the nuclear sites in Iran if it emerges that Iran is breaking out to nuclear weapons; Iran must take into account that Israel possesses second-strike capability if it is attacked with nuclear weapons; and the United States is liable to act with full force against Iran if it attempts to use nuclear weapons against Israel.

At the same time, despite Israel's deterrent capability against Iran and Hezbollah, there is mutual deterrence between the two sides, because even before Iran obtains nuclear weapons, it has created its own deterrence against Israel, based on the large missile arsenals of both Iran and Hezbollah. Even if Israel is superior to Iran and Hezbollah, especially in airpower, Israel must be careful to avoid measures leading to a massive barrage of rockets and missiles.

The Goal of the Adversaries to Deter Iran

Iran is not the only country in the Middle East expending resources on strengthening its deterrent power and using that power against its adversaries. They too, headed by the United States and Israel, and to a lesser extent Saudi Arabia and the other Gulf states, are also taking such actions. Iraq under Saddam Hussein was the main Arab country with the ability to deter and thwart Iran. Since the two Gulf wars, however, Iraq's military power has declined precipitously, and it is no longer able to deter Iran.

The United States possesses the most diversified deterrence tools, led by military capabilities and economic pressure. Since the 1990s, US administrations have usually employed threats of military action against Iran and its proxies, especially against Iran's use of terrorism and its efforts to develop nuclear weapons. These administrations stated that all of the options for stopping Iran, including the military option, were on the table. They preferred, however, not to exercise the military option in order to avoid becoming involved in large-scale fighting, as in Iraq and Afghanistan. The Obama administration, and especially the Trump administration, opted to level heavy economic sanctions against Iran. Iran proved to be sensitive to such pressure, because it was liable to arouse internal unrest and jeopardize the stability of the Iranian regime.

Through these pressures and threats, Iran's enemies seek first and foremost to deter it from continuing its efforts in several key areas:

1. A possible breakout to nuclear weapons
2. Improvement and use of the missile arsenals of both Iran and Hezbollah
3. Iran's consolidation in Syria and the expansion of its influence in Iraq and Lebanon, designed to pose an additional threat to Israel and create a land bridge stretching from Iran to the Mediterranean Sea
4. Iran's intensive involvement in terrorist attacks—directly through Hezbollah, and indirectly through aid to other Shiite militias

In addition, the goal is to enhance the presence and influence of the United States in the Gulf and Iraq in order to rein in Iran's influence in the region and thwart its efforts to disrupt shipping and oil exports by the Gulf states. 

Iran's resistance to its adversaries' efforts at deterrence is mixed. On the one hand, these efforts have borne fruit, and in certain areas, Iran has no suitable answer to the challenges posed by these efforts. First, while the effort to halt Iran's march to nuclear weapons has not stopped Iran's nuclear program, it cannot be ruled out that it will succeed in the future: no nuclear state took 34 years or more to develop nuclear weapons successfully. The main reason for this delay is the international effort, led by the United States, to prevent Iran from obtaining nuclear weapons. On the other hand, Iran has not given up on obtaining nuclear weapons. Its progress brings it closer to the objective, and now it can attain nuclear capability within a few months of a decision to do so.

Second, from time to time, Iran threatens to use its arsenal and that of Hezbollah against its enemies—even against the United States. The Iranian air force commander warned in September 2019 that all of the US bases and ships located up to 2,000 kilometers from Iran—in Afghanistan, Kuwait, Iraq, Qatar, and United Arab Emirates—were within the range of Iran’s missiles, and that in a war, Iran would attack these targets (Zimmt, 2019). In practice, use of the missile arsenals against American and Israeli targets has thus far been limited and cautious in order to avoid stimulating a harsh response against Iranian strategic targets. On the other hand, Iran is ready to use its missile system more extensively against Saudi Arabia, and against ISIS and other organizations in Iraq and Syria.

Third, Syria is Iran's most important regional outpost. Consolidation there is designed to give Iran control and a corridor in the region between western Iran and the Mediterranean Sea, step up the threat to Israel, and strengthen Iran's ties with the Shiite population in Iraq and Lebanon, while safeguarding the Assad regime's continued rule. Iran, however, has met with the Israeli effort to thwart its consolidation, involving hundreds of air strikes against the forces of Iran and the Shiite militias in Syria and Iraq, and against the Iranian effort to ship advanced weapons to Hezbollah in order to upgrade its missile system. Iran has thus far failed to find a solution to the Israeli attacks, despite the many casualties and great damage they have caused, and has been unable to make Israel halt these attacks. The weakness of the Iranian air force, which has refrained from activity in the Syrian theater; the ineffectiveness of the air defense system; and inexperience among the Iranian and Shiite forces in fighting at a distance of hundreds of kilometers from their homes account for this.

Finally, terrorist attacks have a deterrent effect. Major powers are hesitant to intervene in fighting in the Middle East, in part due to fear that their forces will be subject to terrorist attacks. The US army, which entered Iraq in 2003 and stayed there until 2011, lost 4,500 soldiers, with most of the fatalities resulting from terrorist attacks and guerilla warfare conducted by Iraqi militias. To a large extent, the bitter experience of the American forces in Iraq and Afghanistan deterred the administration and other governments from involvement in ground combat with Iranian and Shiite forces.

Conclusion

The Iranian regime faces powerful adversaries posing military, economic, and political challenges and threats. The Iranian response to these challenges is the construction of a set of deterrent tools, at whose base is a large arsenal of diverse missiles built in Iran and in the possession of Shiite militias, most prominently, Hezbollah. This arsenal has a growing ability to strike and damage various targets all over the Middle East, including in Israel. The use of Shiite militias in land combat gives Iran the ability to move forces and weapons over great distances, acquire influence, and act more flexibly over a larger area. Iran also has a large naval array that threatens to disrupt shipping and oil exports through the Gulf; its navy is used primarily in the Gulf, but can also act elsewhere. In addition, Iran operates a network of terrorist organizations in the Middle East, and sometimes also outside it.

There is no doubt that Iran's deterrence arsenal has a considerable effect, even though some of its adversaries are far more powerful militarily. The United States did not respond to the downing of a large spy UAV in June 2019 in the Strait of Hormuz, other than to send an additional 1,000 US soldiers to the Middle East. More importantly, the US administration made no significant response to Iran’s attack on oil facilities in Saudi Arabia out of concern that its response would lead to a large-scale conflict with Iran. Israel has attacked Iranian targets and Shiite militias in Syria and Iraq since 2014, but so far has not attacked the large missile system in Iran, Hezbollah's missile system, or the Iranian nuclear sites. While possible recourse to these arsenals is an alarming scenario for Israel, the main reason for Israel's hesitation is that such attacks will lead to major escalation and the risk of war with Iran.

Iran, however, is also taking care to avoid crossing the red line, and refrains from actions liable to culminate in a large-scale conflict, in which the United States, and even Israel, will take advantage of Iran's weak points. Indeed, Iran's deterrent does not extend to all situations. First, even if the United States is careful to avoid involvement in the conflict with Iran, the Iranian regime recognizes US military superiority, and takes care to avoid dragging the United States into a large-scale conflict. Furthermore, Iran has no solution for the economic sanctions imposed by the US administration, which also jeopardize the regime's stability. Iran is well aware of the special relationship between the United States and Israel, which is likely to contribute to American backing for an Israeli strike against Iran.

Iran also lacks a solution to the hundreds of Israeli air force attacks on Iranian and Shiite militia targets in Syria and Iraq, which hamper Iranian entrenchment in Syria. Iran has made almost no response to these attacks. The Iranian response is also hampered by the fact that Iran and the Shiite militias operate at a distance of hundreds of kilometers from Iran, while the Iranian air force is inferior to the Israeli air force, and is inactive in the Syrian theater. Iran has the option of responding to these attacks with missile barrages from Iran or from Hezbollah's arsenal, but it is probably clear to the regime that the Israeli response to such action will be harsh, and could possibly even include an attack on the Iranian nuclear sites. The same holds for major missile attacks against US targets, which Iran likely realizes will unquestionably result in a massive American response.

Iran regards the use of terrorist attacks as an important deterrence tool. It must be careful, however, to avoid carrying out too many terrorist attacks and turning their use into a system, especially against American targets, lest the American administration respond with severity, including the formation of a bloc of countries against Iran's use of terrorism. This is one of the reasons why Iran uses proxies (mainly Hezbollah) to execute terrorist attacks—in order to obscure its involvement in terrorism.

The power of deterrence is likely to vary over time, for better and for worse. These fluctuations can result from changes in military capability or leadership of one of the parties, changes in the state of allies, or a dramatic act by one of the enemies having an effect on the image it seeks to portray. The killing of Soleimani and Iranian nuclear program head Mohsen Fakhrizadeh probably enhanced the deterrent power of the US administration and Israel, because Iran has so far not responded to these unexpected killings.

How Iran will perceive the deterrent power of the Biden administration versus that of its predecessor is an open question. There is no doubt that President Trump projected a deterrent approach to Iran, with a focus on the United States withdrawal from the nuclear agreement and the stepping up of the sanctions against Iran. There were even deterrent tones in the approach of President Obama. In March 2012, Obama emphasized that both Iran and Israel should take seriously the possibility of an American strike against the nuclear sites in Iran, although the conditions for such an act were not yet fulfilled. During the Obama administration, the United States developed weapons capable of penetrating the defenses of the Iranian nuclear facilities and causing severe damage to them (Kam, 2018; Goldberg, 2012).

In contrast, the Biden administration has so far adopted a softer approach to Iran and the nuclear question. As of now, it has not mentioned the military option against the Iranian nuclear program. It promises that Iran will not obtain nuclear weapons during its term, but has yet to state how it will keep this promise. This approach is liable to be perceived by Iran as weakness, and may have a negative impact on United States deterrence. At the same time, it is possible that judging the Biden administration's deterrent power is premature; it remains to be seen how the United States will respond if Iran attempts to break out to nuclear weapons.

In the current situation, Israel has freedom of action to continue attacking Iranian and Shiite targets in Syria and Iraq, and the Israeli air force is indeed doing so. At the same time, given Iran's many losses in weapons and manpower and the resulting damage to its deterrent power, Iran is searching for a solution that will deter Israel from continuing these attacks—in offensive responses and/or air defense. Thus although Iran has hitherto not responded with real force to the air attacks, it is liable to attempt to do so with a significant action that will enhance its deterrent power, inter alia, following a painful Israeli attack in which many Iranian combatants are wounded, or a strategic Iranian facility is damaged.

In contrast to the Iranian effort to build a strategic outpost in Syria and Iraq, which has so far run into difficulty, Iran is building three larger deterrent bases: the huge missile system in Iran; Hezbollah’s large and growing missile system, over which Iran wields direct influence; and above all, the infrastructure and ability to develop nuclear weapons in the future. These three elements, along with the missile arsenal in the hands of the Iraqi Shiite militias linked to Iran and the Houthis in Yemen, constitute the main security threat to Israel. The deterrent power of these three elements is indicated by the fact that Israel has not yet attempted to attack them, despite the gravity of the threat that they pose. This threat is aimed not only against Israel; it is also aimed at the United States and its Arab allies, headed by Saudi Arabia. For this reason, it is important for Israel to discuss the Iranian nuclear threat with the current administration in Washington, as well as the threat already posed by the stores of missiles.

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