By Eric Vandenbroeck and co-workers

Israel’s Latest Wars are Changing Tehran’s Strategic Calculations

The recent conflicts in the Middle East have ignited open debate among Iran’s political elite over whether the country should weaponize its vast nuclear program. The rationale for doing so, from Iranian leadership’s perspective, appears more convincing than ever.

Above all, Iran needs to reestablish deterrence equilibrium with its longtime foes Israel and the United States. Traditionally, to deter its adversaries from attacking or implementing regime change, Tehran relied on a three-pronged approach focused on missiles, militias, and a nuclear program.

To offset its weak air force, Iran invested heavily in its missiles program, making its arsenal one of the most advanced in the region. Iran also anchors its asymmetric warfare strategy through the so-called “forward defense” policy of using militarized nonstate actors to encircle Israel and the U.S. regional military presence and to mobilize these forces to attack if required. Iran has cultivated its relations with groups that are hostile to the United States and Israel, building the so-called Axis of Resistance, providing them with arms—including sophisticated missiles and drones—as well as training and financial support.

However, Iran’s missiles capabilities and the Axis of Resistance have taken a hit in recent months. The Israeli onslaught against Iran’s most trusted partner, Hezbollah in Lebanon, has delivered a blow to its arsenal, fighters, and command and control structure. Iran was left humiliated by Israel’s ability to assassinate Hamas leader Ismail Haniyeh while he was in Tehran this summer. Following the killing of Hamas leader Yahya Sinwar this month, Israel seems determined to keep upping the ante to establish a new regional order.

Although Hamas and Hezbollah will continue to undermine Israeli security, the ability of these groups to mobilize in defense of Iran seems severely diminished while they fight for their own survival. Meanwhile, the United States has doubled down on its efforts to shield Israel, moving new anti-missile systems into the country, together with American troops to operate them, in a bid to defang future attacks from Iran and its allies.

 

How a Campaign Against Hezbollah Could Lower Iran’s Inhibitions

Last April, it appeared as though escalation between Israel and Iran could plunge the entire Middle East into conflict. Israel’s strikes on the Iranian consulate in Damascus prompted Iran to retaliate by launching a barrage of missiles and rockets into Israel—the first time that Iran had openly attacked the country. But after Israel responded in a relatively muted way, both countries moved on from the confrontation. Observers, too, put aside their most acute worries, comforted by the fact that both countries had shown that they had no interest in a wider war.

This conclusion, however, was premature. In September, Israel intensified its campaign against Hezbollah, the Iranian-backed paramilitary group operating in Lebanon. This marked an important shift: it suggests that Israeli leaders decided they wanted to actively reshape the balance of power in the Middle East. Much more than its actions in Gaza, Israel’s war against Hezbollah threatens Iran’s ability to project power and profoundly diminishes its ability to deter Israeli interventions into its own domestic politics and nuclear program. The weakening of Iran’s position will benefit Israelis in the short term. But in the long term, it will significantly increase the risk of a regional war and even the likelihood that Iran will acquire nuclear weapons. To avoid being dragged into yet more conflict in the Middle East, the United States must work to restrain further Israeli action and stabilize the balance of power.

 

Phase Shift

Deterrence, at its core, is the ability of one actor to alter the cost-benefit calculus of another in order to prevent unwanted actions—usually in an effort to preserve the status quo. Yet deterrence is rarely synonymous with absolute peace; rather, it is about preventing an adversary from crossing specific redlines. During the Cold War, for example, the United States and Soviet Union were highly effective in deterring each other from launching preemptive or direct attacks but still conducted decades’ worth of proxy wars, arms sales to adversaries, and outright invasions of third countries. The United States has been effective thus far in deterring China from invading Taiwan but has not prevented China from undertaking other provocative actions in the South China Sea. The tendency in international politics whereby states are deterred from direct attacks in favor of indirect action is at the heart of the stability-instability paradox theorized in security studies—in which stable nuclear deterrence encourages more aggression using conventional military methods—and has been a central part of Iranian strategy in the Middle East.

To that end, deterrence is not only relevant to shaping decisions about whether to act. It also plays an important role in shaping military strategy once hostilities have begun. Successful deterrence may then simply be about managing escalation and preventing specific types of strikes that would damage either country’s fundamental ability to maintain its security. Which military strategy a country chooses is almost always—and should be—informed by its adversary’s expected reaction. U.S. President Joe Biden’s administration, for example, has been extraordinarily careful to define how Ukrainian forces can use American weapons in their fight against Russia, because Russia’s threat of nuclear escalation is at least partly credible. Put another way, the strategy the United States has pursued to help Ukraine has reflected Russia’s efforts to deter it.

Iranian Basij militia parade

Prior to this September, the war in the Middle East largely appeared to be contained. For the most part, Israel’s response to Hamas’s devastating October 7 attack was confined to the Gaza Strip. Although Israeli leaders have stated since October 7 that they want to eliminate Hamas, that group was less powerful and less ideologically aligned with Iran than Hezbollah is. Israel’s exchanges with Iran and Hezbollah mostly conformed to the tit-for-tat deterrence pattern that had defined its relations with its neighbors for almost two decades.

Even as recently as April and May, long-standing deterrence norms shaped the strategy that both Israel and Iran employed. Consider Iran’s response to Israel’s strike on its Damascus consulate: ahead of its retaliatory missile strike on Israel, Iran’s leaders went out of their way to ensure that both Israel and the international community knew that their reprisal was a direct response to the consulate attack, not the beginning of a larger campaign against Israel nor an indication of any desire to escalate. The missile strikes themselves—aimed outside of large population centers and easily intercepted by Israel’s missile defense—did not suggest that Iran was looking to seriously hurt Israel. Iran’s leaders did not pursue a more damaging military option because they both sought to deter and were deterred by Israel: the Iranian strategy appeared to be driven by the desire to deprive Israeli leaders of a reason to launch a further escalatory response.

But Israel’s recent escalation of hostilities into Lebanon in response to progressively more aggressive incursions by Hezbollah has decisively redefined the deterrence dynamic that previously kept conflict in the Middle East from escalating. In the status quo that previously defined the region, Iranian proxy groups’ harassment of Israel enabled Iran to avoid direct confrontation. Hamas and, in particular, Hezbollah functioned as deterrents to Israeli military action against Iranian interests by keeping Israel distracted. The threats Hamas and Hezbollah posed to Israel allowed Iran to exert power across the region while holding Israelis indirectly at risk, which—combined with Israel’s deterrence in the form of its superior military power—produced a stable equilibrium.

Over the course of the past year, however, the fallout from October 7 has changed both Israeli leaders’ and citizens’ risk calculus. Both have become much less willing to accept risk from Iranian proxies on Israel’s perimeter and more willing to accept escalation with Iran. As the military campaign in Gaza turned in Israel’s favor, returning to the pre-October 7 status quo became less acceptable to Israeli leaders. U.S. assistance in the form of munitions and an increased American presence in the region have boosted Israel’s military capabilities; Israel’s domestic mood and political situation have pushed the country’s leadership to pursue a broader regional reorientation; Israeli leaders have felt fewer constraints on their military actions as the United States’ presidential election distracted the U.S. government; and Iran’s own domestic challenges have reduced its ability to support Hezbollah.

 

Bad Wager

These factors have led Israel to reject the status quo. As of September, Israel appears to be working to eliminate Hezbollah entirely as well as Hamas, thereby permanently changing its balance of power with Iran. The removal of both Hamas and Hezbollah from the military balance in the Middle East will remove a critical piece of Tehran’s leverage, leaving Iran with fewer ways to hold Israelis at risk and deter them from taking offensive action. In the near term, given that Iran will have fewer proxies with which it can indirectly harass Israel and respond to Israeli actions, Iran will have less ability to menace the region and respond to the actions of both Israel and other regional players. That will temporarily heighten the threshold for Iranian offensive actions, resulting in a region that looks more stable—particularly to Israelis.

Yet disabling Hezbollah as well as Hamas, even temporarily, will likely have significant negative long-term effects on both Israel and the Middle East. Iran will be pressed to find other sources of leverage to deter Israel’s interference in its nuclear programs and other activities, making it much likelier to engage in horizontal escalation—when a state widens the scope of a conflict beyond its initial geography. In the weeks leading up to Israel’s October 25 strikes inside Iran, Iranian officials reportedly threatened to retaliate against the United States as well as any Arab countries that allowed Israel to use their territory or airspace to launch an attack.

It is vertical escalation, however, that poses the greatest risk to Middle East security—and Israeli leaders are taking a big gamble by increasing their tolerance for it. The destruction of their proxies raises the threshold for Iranian military action, but it also limits Iran’s ability to respond to Israeli actions asymmetrically. Should Iranian leaders’ efforts at horizontal escalation prove ineffective, they will perceive that they have little choice but to threaten serious military action against Israel using larger or more destructive weapons.

If Iran does decide to act militarily, its actions will thus likely be far more direct and escalatory. As China’s first nuclear test in 1964 prompted India to test a weapon in 1974, which in turn drove Pakistan to accelerate its nuclear program and test a weapon in 1998, in the long run, Israel’s escalating military campaign may constitute Iran’s final incentive to cross the nuclear threshold. Iran possessing nukes represents an existential threat to Israel’s security in a way that terror groups—despite their horrific actions—simply never did.

 

Unintended Consequences

The Middle East’s shifting balance of power also transfers considerable risk onto the United States and its regional partners. Should Iran accelerate its pursuit of a nuclear weapon, the United States will be forced to become further involved in Israel’s wars even as its leverage in the region is diminishing. Israel is becoming increasingly prone to rejecting U.S. advice and seeks to reduce its reliance on U.S. military aid. Moreover, the prospect of Iranian attacks against U.S. troops and partner nations will require the United States to direct more resources toward the Middle East just as it ought to be shifting its focus to deterring Chinese aggression in maritime East Asia.

 

Iran’s biggest Achilles’s heel

Perhaps Iran’s biggest Achilles’s heel is its self-restraint. Over the past year, Iran’s supreme leader, Ayatollah Ali Khamenei, has repeatedly held back from a direct war with Israel and the United States. He has also shied away from triggering a full assault by the Axis of Resistance front. Israel has interpreted this restraint as a weakness and exploited it.

This shift in regional deterrence has strengthened the argument in Tehran favoring a nuclear umbrella. Iran has already obtained nuclear threshold status, placing it at the tipping point of weaponization. Iran can develop enough material for a nuclear bomb in just over a week, with some experts assessing that it could build a nuclear warhead to carry these bombs within several months. In the same way that India and Pakistan achieved a relative cold peace, Tehran may look to check Israeli behavior through rebalancing the nuclear playing field.

Another argument for why Iran could dash for the bomb is that the country has already paid the high cost of becoming a nuclear weapons state without receiving the perceived benefits of having the bomb.

Ever since the Trump administration withdrew from the 2015 nuclear deal, which Iran was in full compliance with at the time, the United States has imposed its largest-scale sanctions to date against Iran. Western relations with Tehran further plummeted over Iran’s abysmal human rights record, its regional posture, and military assistance to Russia during its full-scale invasion of Ukraine. Given the anti-Iran sentiment across Western capitals, the Iranian leadership would be

correct to conclude that major U.S. sanctions relief of the type seen in 2015 is not on the horizon. If Iran is already being treated as a nuclear pariah state by the West, then why not secure the perceived security benefits of going nuclear?

Israel’s strategy is a familiar one. Weaker partners in an alliance will always seek to transfer the risk of escalation onto the stronger partner, a phenomenon that political scientists call “moral hazard.” It is therefore up to U.S. leaders to define the limits of the United States’ willingness to support Israel’s strategy and to communicate privately to their Israeli counterparts that they will not support further escalation. Incoming U.S. President Donald Trump’s administration must rethink its uncritical support of Israeli Prime Minister Benjamin Netanyahu’s government, clarifying and restricting how and when that government can use American weapons and munitions. And it must diplomatically reassure the region’s other actors that the United States will be a moderating influence rather than an aggravating one. Without these changes, the potential for escalation in the Middle East will only grow.

Finally, the broader geopolitical conditions today mean the costs associated with Iran becoming a nuclear state are lower than a decade ago. Tensions between world powers now make it increasingly unlikely that Russia, and possibly China, will stand in Iran’s way. Tehran can also capitalize on the Ukraine war by pushing to trade its military equipment—which Moscow desperately needs—for Russian nuclear know-how, technology, and defense at the U.N. Security Council. The United States already fears this could be happening.

Against this backdrop, those inside Iran favoring nuclear weaponization likely see two choices ahead: either Iran’s nuclear facilities are eventually destroyed by Israel and the United States first, and then Tehran stumbles toward nuclear weapons over a longer timeframe with depleted resources, or Iran starts the weaponization now while it has advanced nuclear capabilities and Israel is bogged down in Gaza and Lebanon. Iranian strategists may be swayed for the latter option when faced with a weakened Axis of Resistance, a formidable Israeli-U.S. military force and an Israel poised to strike at Iranian nuclear sites. Despite the strong likelihood that the country will be bombed throughout this process by Israel and the United States, Iran’s leadership may conclude it can bear the brunt of military action and come out of it stronger.

 

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