Opinion | Why Israel Is Worried About Iran’s Nuclear Ambitions

Iran’s supreme leader, Ayatollah Ali Khamenei, learned the limits of his foreign policy strategy this week: Even well-armed and well-trained surrogate forces can prove unreliable if a determined modern army disables them.

After the death of Hassan Nasrallah and many of the other members of the upper echelons of the Lebanese Hezbollah, the clerical regime’s thwarted ballistic-missile attack on Israel on Tuesday was an attempt to diminish the humiliation that Tehran has felt after Israel rapidly deconstructed Iran’s most cherished protégé. With Hezbollah as a model and partner, Tehran had perfected Islamist imperialism on the cheap: Proxies spread the faith and mauled Iran’s enemies while shielding it from direct retaliation.

But as the Israeli offensives in Gaza and Lebanon have revealed, an aspiring regional hegemon with limited conventional capacity needs more firepower and deterrence than proxies alone can deliver. Israel may have already destroyed much of Hezbollah’s most dangerous missiles, launchers and missile crews. And given the two-time failure of Iran to overwhelm the Jewish state’s air defenses, the regime’s huge investment in ballistic and cruise missiles has also proved suddenly wanting.

Where, then, might Ayatollah Khamenei turn next? Despite the supreme leader’s stated religious objections to nuclear weapons, Iran has been steadily making progress on its nuclear weapons capabilities over the past year. It is now, according to the U.S. government, down to a one-to-two-week breakout time to produce enough uranium for one atomic bomb, though it could take it several months to field a nuclear weapon.

With its proxy fighters under siege and its conventional weapons proving insufficient, Tehran may be closer than ever to crossing the threshold and building a nuclear weapon. Iran’s missile barrages could provoke Prime Minister Benjamin Netanyahu of Israel to risk a strike aimed at its nuclear facilities and deny Tehran the only weapon that could guarantee its freedom to maneuver.

For decades, the Iranian leadership has wanted to project power at arm’s length, seeing that its legitimacy rested on exporting the Islamic revolution abroad. Conditions were ripe for this strategy in the post-9/11 Middle East. When the regional state system essentially collapsed, Tehran marched into the vacuum. The Islamic Republic’s proxies saw success in the civil wars in Iraq and Syria and demoralized America even after the 2007 U.S. surge in Iraq routed many of Iran’s local allies. In Yemen the Iranian-supported Houthis, whose Shiite radicalization is recent but deep, wore down the alliance of Saudi Arabia and the United Arab Emirates.

This was essentially the status quo shattered by Oct. 7 — Iranian power rising in the Levant, Iraq and the Arabian Peninsula, while America and Israel focused on expanding the Abraham Accords to Saudi Arabia.

Though Iran’s state media is filled with stories of Gazan deaths, the regime most likely wasn’t too perturbed in private by Mr. Netanyahu’s aggressive response to Hamas’s brutal attack. In fact, the strong response by Israel to the Oct. 7 attacks is a significant propaganda victory for Tehran, given how it produced a global eruption of pro-Palestinian and anti-Zionist sentiments.

Once Israel intensified its assault on Hezbollah, that calculus changed. For Iran, the battle on Israel’s northern frontier is altogether different. The Islamic Republic has backed Hezbollah since its founding in the 1980s and has used it as an instrument of its terrorism from the Levant to South America. Hezbollah and its arsenal of missiles serve as Iran’s second-strike force should Israel ever be tempted to target its nuclear installations.

Having successfully fended off Iran’s volley of ballistic missiles with America’s help, Israel is confronting a dilemma. It has vowed to retaliate, and reportedly cited Iran’s nuclear facilities as potential targets, along with Iran’s oil rigs and air defense systems. But taking out Iran’s nuclear program could lay the groundwork for a sustained direct war with Iran that Israel will struggle to maintain while it tries to contain Hamas and Hezbollah. And if it undertakes a significant counterattack against Iran but doesn’t bomb the nuclear facilities, it will leave intact the one weapon that a wounded theocracy will need to deter future Israeli actions.

While Israel’s military and civilian leadership debate the scale of the response, the United States, its most critical ally and military backer, is in crisis-management mode, continuing to seek de-escalation despite months of being unable to deliver on this goal. President Biden has said he would not support an Israeli attack on Iran’s nuclear sites. But the president and presidential candidates have also declared that Iran will never be permitted to have a bomb, which doesn’t mesh easily with bipartisan calls for the United States to stop getting dragged into “forever wars.”

While camps in Jerusalem and Washington may disagree on the best path forward, their close alliance may be the only remaining brake on Iran’s atomic ambitions. Israel’s recent string of intelligence successes, especially the bombing that killed Ismail Haniyeh, a top Hamas leader, in a compound operated by the Revolutionary Guards in Tehran, must make Ayatollah Khamenei wonder whether a secret order to assemble an A-bomb would simply leak and provoke Israeli or American pre-emption.

The post-Oct. 7 Middle East still offers the Iranian theocracy reasons to hope. Israel has badly battered its proxies, but Hamas and Hezbollah will almost certainly survive. The conflagration has derailed Saudi-Israeli normalization, and, for now, a U.S.-Saudi defense alliance that would have posed a major threat to Tehran. The Saudi and Emirati royals who once vehemently denounced Iranians’ machinations and fed Israeli hopes for a grand entente against the Shiite foe have taken a softer line, given the deaths of tens of thousands of Palestinians.

If in the not-too-distant future the clerical regime can test a nuclear weapon, then it will overnight diminish any power that Israel and America have in the region. The United States has never attacked a nuclear-armed state. It’s a good guess that Israel, which is widely believed to have nuclear weapons though it has not declared them, will not attack a nuclear-armed state. And the long-held nuclear doctrine of mutually assured destruction would almost certainly restrict Israel more than Iran. Iran has already demonstrated a willingness to attack a nuclear-armed Israel. Tehran has deadly proxies; Israel does not.

Becoming a nuclear state could offer a new way for Ayatollah Khamenei to promote Iran’s power at home and abroad, while neutralizing the possibility that his decision to attack Israel again this week would lead to a conventional escalation in which Iran can’t compete. Authoritarian states are acutely dependent on the awe they project. Foreign defeats inevitably have repercussions at home.

Mr. Gerecht is a resident scholar at the Foundation for Defense of Democracies. Mr. Takeyh is a senior fellow at the Council on Foreign Relations.

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