What are Iran’s Options after Nasrallah’s Death?

The assassination of Hezbollah’s Secretary-General Hassan Nasrallah in strikes in Beirut on 27 September narrowed Iran’s already slim options. Beyond the usual regime rhetoric consisting of threats to retaliate against the ‘Zionist regime’, Iran has not yet articulated a coherent message to indicate how it will respond. There is considerable debate within the Iranian system, split between hardliner calls for direct action and others that caution against falling into an Israeli ‘trap’ that would be to Iran’s strategic detriment. The reality is that Tehran has no good options, and any potential retaliation against Israel will have limited impact given Tehran’s diminished leverage.

Vice President for Strategic Affairs Mohammad Javad Zarif has said that Iran’s response to Nasrallah’s killing ‘will be happening at the appropriate time Iran chooses’. But increasingly, as the Arab world reels from the assassination during Israel’s relentless campaign against Hezbollah and the devastating civilian casualties in Lebanon, pressure is mounting on Iran to act. What some had once seen as Tehran ‘playing the long game’ is now being criticised as little more than chronic inaction – a signal of Iranian weakness. Detractors argue that Iran’s failure to respond to the assassination in Tehran of Hamas political leader Ismail Haniyeh on 31 July was a grave miscalculation, one that paved the way for Israel to ramp up its offensive against Hezbollah.

Iran’s regional security policy is based on two fundamental pillars: a latent military nuclear capability and the deployment of a network of aligned militia, or the ‘Ring of Fire’, which includes Hezbollah in Lebanon, Hamas and Islamic Jihad in Gaza, armed groups in Syria and Iraq, and the Ansar Allah, or Houthi movement, in Yemen. The first pillar has served to constrain Iran from taking overt belligerent action against Israel out of fear that an Israeli retaliation on its territory would damage its nuclear programme, setting it back by years and at great cost. The second pillar by definition requires ongoing organisational resilience and offensive military competence of its allies.

The death of Nasrallah, who personified Iran’s ‘resistance’ movement in the region, has altered the calculus for Iran. First, Iran’s extended deterrence through its so-called ‘axis of resistance’, which allowed it to externalise armed violence to Gaza, Lebanon and other theatres while claiming plausible deniability, is now under unprecedented pressure. This is a moment of reckoning, where Hezbollah and its supporters recognise that many may have overestimated Iran’s military capability and ideological resolve. Second, the ‘unity of arenas’ doctrine, which compelled different Iran-linked militia to open a multi-front and coordinated offensive against Israel, is now also at risk of buckling. The missiles launched from Lebanon and Yemen have had limited impact on Israel. If Iran were to feel directly threatened by an Israeli attack on its nuclear programme, oil refineries, trade routes, or sensitive national infrastructure, this might force Tehran to risk direct confrontation – but this remains unlikely, at least for now.

The possibility of a limited Israeli ground incursion into Lebanon remains high. Israeli decision-makers appear to continue to debate the inherent risk of such an operation, including the likelihood of Israeli troop casualties in the event of guerilla-style fighting by Hezbollah in southern Lebanon. Part of the Israeli calculus now is that the threat of an invasion may create enough pressure to persuade Hezbollah’s diminished command structure to agree to withdraw north of the Litani River line in accordance with UN Resolution 1701. But this would only be a partial resolution to what Israeli officials define as an unsustainable threat to its northern communities. Having created conditions on the ground that are to its advantage, Israel may decide that this is an unmissable opportunity to conduct a limited ground operation to clear out parts of southern Lebanon. Without a ground operation, Israel’s main objective – allowing the more than 60,000 displaced Israelis to return to their homes in the northern kibbutzim – will not be fully achieved.

Iranian President Masoud Pezeshkian’s more conciliatory signalling at the UN General Assembly in New York about reopening dialogue with the West constitutes a form of doublespeak. Tehran needs economic sanction relief to lift its beleaguered population out of domestic instability, but sanctions are not the only culprit behind Iran’s economic hardship. Corruption, poor governance and fiscal policies, and the significant financing of proxy groups, are other signs of systemic failure by the regime.

Options in Iran’s Strategic Toolkit

First, the Islamic Revolutionary Guard Corps and senior leaders may mobilise militia in Iraq and Syria against Israeli, US and UK targets, but refrain from direct confrontation. Far short of strategic success, this option will not meet the threshold of the Iranian response expected from the country’s allies to reestablish deterrence. There are complications in both Iraq and Syria’s internal dynamics to consider. If Iran-aligned militia in Iraq target US military assets in Iraq, Syria or Jordan in an attack that leads to American casualties, this will invite a military response on Iraqi territory – an undesirable scenario ahead of the US presidential election and the planned drawdown of US forces next year. In Syria, Bashar al-Assad’s priority is regime survival, which will undoubtedly come into question if the country is drawn into a wider war by Iran. The appetite for more sustained involvement is not there.

Second, Iran may try to mobilise Houthi attacks against sensitive targets inside Israel. With Hezbollah now in crisis, the Houthis may gain more operational significance. An escalation in Houthi-led harassment and attacks on commercial shipping in the Red Sea may be expected. Additionally, other actors in the Iran-linked resistance may attempt asymmetrical attacks on Israeli and Western targets, such as diplomatic missions overseas, or suicide attacks inside Israel or the West Bank by a decentralised Hezbollah and Islamic Jihad.

Third, and the least likely option, is for Iran to launch attacks on Israel. While this may salvage Iran’s credibility with its core base inside Iran and across its axis, the risk is that, like its attack on 13 April, the barrage of missiles will be intercepted by Israel’s Iron Dome system and by the US and its Arab allies. This would further erode Iran’s projection of military strength and cause a legitimacy crisis inside Iran.

Ultimately, Iran knows how to play a calculated long game and is unlikely to act impulsively to harm its wider regional strategy. Tehran may prefer to bide its time to support Hezbollah as it reconstitutes around a new leader, purge internal defectors accused of collaborating with Israeli intelligence services, and rebuild Hezbollah’s command structure and communication systems. Such a ‘strategic patience’ approach may be reinforced by a focus on Iran’s relationship with Russia and China.

If a negotiated ceasefire in Gaza was not enough of a priority before, it is even more important now. It may now be the crucial lever needed to initiate a process of de-escalation. Such a move could constrain Hezbollah’s remaining units, the Houthis, and other militias from launching provocative attacks on Israeli and Western targets in the short term. It remains to be seen whether Israel launches a ground incursion, and if it does, will this (finally) be the red line that Iran cannot tolerate? Since the 7 October attacks, Iran has shown that the axis of resistance was created to shield it from the direct line of fire and to avoid confrontation. This fundamental ‘Iran-first’ perspective does not appear to have shifted, but if Iran cannot provide extended deterrence for its allies in the region, it may be seen to have little to offer at all.

The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.

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