By Eric Vandenbroeck and co-workers

Will Iran and Russia’s Growing Partnership Go Nuclear?

In July 2015, General Qasem Soleimani, former commander of Iran’s elite Quds Force, secretly traveled to Moscow to discuss an emergency plan to rescue the Assad regime in Syria, which had lost control of roughly 80 percent of Syrian territory in four years of civil war. Russia had just helped broker the 2015 Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA).

Soleimani’s trip, disclosed three months later, took place in defiance of UN travel sanctions tied to Iran’s nuclear program and threatened to undermine it. Yet the meeting would initiate a decadelong evolution of the Russian-Iranian relationship, from tactical cooperation in Syria to close partnership today, culminating in the signing of a strategic partnership agreement between the two countries in January 2025.

The Russian intervention in Syria forced Moscow to engage in a delicate balancing act between Iran and Israel, with which it had a relatively constructive diplomatic relationship. While coordinating military operations with Iran, Moscow maintained diplomatic channels with Israel and even acted to constrain Iranian influence in Syria. But Russia’s invasion of Ukraine in 2022, along with its response to Hamas’s October 7 attacks in Israel, upset this balance, as Moscow’s growing dependence on Iranian military technology drove it closer to Tehran. A decade after Soleimani’s visit, Iran and Russia have forged unprecedented ties, strengthened by their shared isolation from the West and by military cooperation in Ukraine. Russia, once an architect of the deal to restrict Iran’s nuclear program, has evolved into a potential enabler of Tehran’s nuclear ambitions.

With Iran’s axis of resistance weakened by Israel’s response to October 7, the fall of the Assad regime, and fighting in Ukraine entering its third year, Moscow and Tehran have turned to each other. Iranian military support has become critical for the Russian war effort, and Russian-assisted nuclear development is fast becoming Iran’s most powerful leverage against Israel and the West. For the United States and Israel, this new relationship risks cementing the emergence of an influential anti-Western axis. But a “maximum pressure” campaign against Iran, the preference of many inside the Trump administration, may push a nuclearizing Iran closer to Russia. Instead, the United States must engage in a delicate diplomatic maneuver of its own: stopping Iran from acquiring nuclear weapons without driving Tehran into Moscow’s arms.

 

High-Wire Act

Syria served as a crucial testing ground for Iranian-Russian military collaboration. Despite lacking formal defense commitments or previous joint operational experience, Moscow and Tehran developed comprehensive frameworks for military and diplomatic coordination, beginning with Russia’s military involvement in Syria in the fall of 2015. Their integrated air and ground operations allowed Bashar al-Assad’s regime to temporarily recover key territories, effectively prolonging the Syrian dictator’s rule for another decade. These battle-tested coordination mechanisms would come in handy as Russia expanded military cooperation with Iran following its invasion of Ukraine. Existing channels of cooperation, such as integrated command structures, intelligence-sharing protocols, and procurement channels forged in Syria were put to use against Ukraine. Russia also turned to Iran for direct military support, particularly in drone technology and joint defense production.

Russia cultivated a careful diplomatic relationship with Israel in parallel to its military cooperation with Iran. What began as a deconfliction channel established to prevent inadvertent military clashes in Syria evolved into active diplomacy between Israeli Prime Minister Benjamin Netanyahu and Russian President Vladimir Putin, yielding ten high-level meetings focused on Russia’s support for Assad and Iranian involvement in Syria between 2015 and 2019. Putin agreed to limit Iran’s presence in Syria, especially in the Golan Heights, close to the Israeli border, and in return, Netanyahu agreed to allow Assad’s forces to return to the Golan Heights and limit Israel’s strikes in Syria to avoid further destabilizing the regime.

Netanyahu used his relationship with Russia to his advantage domestically, touting his close ties with Putin in his 2019 election campaign to demonstrate his credentials as a shrewd actor on the global stage. Israel, meanwhile, pursued its own agenda through its “campaign between wars,” which aimed to prevent Iran from establishing permanent military infrastructure in Syria and to disrupt Iranian supply routes to Hezbollah through covert operations and airstrikes.

Before the 2022 expanded invasion of Ukraine, Russia strained to preserve its relationships with both Israel and Iran as they pursued their own, conflicting interests, revealing the difficulty of maintaining its regional balancing act. On the one hand, Moscow turned a blind eye to Israeli operations against Iran and its non-state allies in Syria. According to WhatsApp communications recently captured by rebel group Hayat Tahrir al-Sham (HTS) in Damascus, it even tried to arrange a Kremlin meeting between Assad and then Mossad chief Yossi Cohen in late 2019, to limit Iran’s influence in Syria (Assad ultimately withdrew). But on the other, it collaborated with Iran to prop up the Assad regime and was secretly directly arming Hezbollah. According to Israeli intelligence, over 70 percent of Hezbollah armaments captured in Lebanon were Russian-made, supplied directly through Russia’s Tartus naval base in Syria. Russia may have been able to juggle its relationships with both countries if not for the 2022 invasion of Ukraine, which changed the dynamics in Syria and caused the Kremlin’s strategy to collapse under the weight of its contradictions.

As sanctions intensified, Russia, finding itself increasingly isolated from the West, saw Iran as a reliable partner in two conflicts. As it drew ground forces away from Syria and into Ukraine, Moscow maintained its air presence at the Khmeimim air base but delegated ground support for the Assad government to Iranian-backed forces. These adaptations initially proved effective in preserving Russian influence in Syria. But they further entrenched Iranian military presence in the region, worrying Israeli officials, who responded by increasing attempts to limit Iranian involvement in Syria. The new dynamic was evident in May 2022, when Russian forces based in Syria used Russian-supplied S-300 antiaircraft missiles against Israeli jets attacking targets in northwest Syria for the first time. Still, Israel remained largely quiet about the Ukraine war, to preserve Russian cooperation in Syria. In a March 2023 interview, Netanyahu stressed that Israeli pilots were operating “in very close proximity” to Russian pilots. The uneasy equilibrium Russia had achieved was growing increasingly precarious. The events following Hamas’s October 7 attack would destroy it.

Iranian President Masoud Pezeshkian and Russian President Vladimir Putin in Moscow, January 2025

 

Can’t Please ’Em All

Moscow’s already deepening reliance on Iranian support in Ukraine broke the path for deeper Russian-Iranian cooperation in the Middle East. As Iranian-backed actors, including the Houthis in Yemen and militias in Iraq and Syria, mobilized across the region to attack Israel after October 7, Russia abandoned any pretense of neutrality. In Yemen, according to the Wall Street Journal, Moscow provided satellite data through IRGC operatives to enhance Houthi targeting capabilities against shipping vessels in the Red Sea and agreed to a $10 million weapons deal with the Houthis, brokered by Tehran, under the guise of a humanitarian aid package, before it was ultimately scuttled. In Lebanon, it facilitated the transfer of sophisticated weaponry to Hezbollah, including advanced antitank guided missiles later deployed against targets inside Israel. Russia also granted Iranian-backed forces greater operational freedom in the Syrian Golan Heights. Perhaps most indicative of Russia’s shift was the refusal of Putin and Russian officials to issue any condemnation or rebuke of Hamas in the days following October 7. Rather, on October 13, Putin compared the IDF to the Nazis, telling journalists that the IDF’s plans in Gaza were “comparable to the siege of Leningrad during the Great Patriotic War.”

The Israeli response to October 7 dealt decisive blows to Iran’s network of proxies. In addition to targeting Hamas in Gaza, Israel established effective land and air blockades that severed Iranian troop movements and logistics into Syria for Hezbollah by the end of 2023. The campaign eliminated 16 senior Hezbollah commanders, including its leader, Hassan Nasrallah, and decimated the organization’s presence in southern Lebanon and its strongholds in Syria. Despite its long-standing policy of avoiding direct confrontation with Israel, in April and October 2024, Iran launched two separate missile and drone attacks against Israel. Israel’s October retaliation, which targeted missile-manufacturing sites and air defense sites across the country, had far-reaching consequences. The attack destroyed four Russian supplied S-300 systems and Iranian air defense systems, crippling Iran’s ability to defend itself from future strikes.

The immediate escalation after October 7 initially benefitted Russia by diverting Western attention and resources away from Ukraine and into the Middle East. But ultimately, Moscow came to suffer the consequences of Iran’s regional setbacks. After a decade of successful Russian military assistance, the Assad regime suddenly collapsed in December 2024. Unlike in 2016, when Iranian ground forces and Russian air support succeeded in repelling rebel forces during the siege of Aleppo, neither patron could launch a rapid counteroffensive this time. Iranian-backed forces had been severely degraded by Israeli strikes, and Israel’s air force was in position to prevent Iranian attempts to reach Damascus. Russia was too preoccupied with waging war in Ukraine to defend Assad.

Just how deeply intertwined the wars in Ukraine and the Middle East have become was highlighted when Ukraine extended its fight against Russian influence directly into Syria. Kyiv sent about 20 experienced drone operators and 150 advanced first-person-view drones to rebel headquarters in Idlib to support HTS.

Facing inevitable defeat, Moscow orchestrated a hasty but carefully planned exfiltration of Assad from Damascus. Russian state media amplified reports in the Turkish press that, in exchange for safe passage, Assad provided a comprehensive list of Syrian strategic assets, which Israel subsequently targeted. But these face-saving measures could not obscure the fundamental unraveling of Russia and Iran’s position in Syria. In response to these defeats, Iran moved to rapidly expand its nuclear program, with Russia, no longer able to balance its diplomatic commitments to two regional rivals, now its new leading partner. The two countries lost Syria, but, in the fall of Damascus, they gained each other.

 

Learning to Love the Bomb?

Its proxies and conventional capabilities weakened and its “forward defense strategy” challenged, Tehran has begun to reconsider its nuclear option. Currently, Iran is assumed to be a threshold nuclear state, possessing the essential components for nuclear weapons, including uranium enrichment technology, technical expertise, delivery systems, and facilities, but it has not yet decided to weaponize. Full weaponization would require a challenging process that risks detection either by International Atomic Energy Agency inspectors or by Western intelligence agencies, as well as preemptive strikes from Israel or the United States. Iranian officials have begun hinting at potential changes in Iran’s nuclear posture, which formally eschews nuclear weapons development, with some hawkish figures openly calling for nuclear acquisition. In April 2024, Brigadier General Ahmed Haq Talab, commander of Iran’s Nuclear Centers Protection and Security Corps, declared that if Israel raided one of Iran’s nuclear facilities, the regime could “revise” its nuclear doctrine. Kamal Kharrazi, a former official, warned that if Israel “dares to damage Iran’s nuclear facilities, our level of deterrence will be different. We have no decision to produce a nuclear bomb, but if the existence of Iran is threatened, we will have to change our nuclear doctrine.”

Russia’s embrace adds further complexity to Iran’s nuclear equation. Moscow’s position has undergone a dramatic transformation. Once a supporter of UN Security Council sanctions on Iran’s nuclear program and a key architect of the Iran nuclear deal, Russia has come to view Iran as a critical ally and partner with which to project strength in its own neighborhood and beyond it. Iranian military support in Ukraine has not only become crucial for Moscow’s war effort; it has also led Russia to link the Iranian nuclear program to broader tensions with the West. Russia is using the West’s attention to the threat of a nuclear Iran to stoke tensions and divert focus from Ukraine.

Though the exact nature of Russian aid to Iran is unknown, U.S. and Israeli officials have tracked their evolving partnership with growing alarm. In July 2023, CIA Director William Burns highlighted Russian cooperation on Iran’s space launch vehicle program, citing the presence of Russian technicians “working on the space launch vehicle program in Iran and other aspects of their missile programs.” Significantly, such assistance is directly applicable to ICBM development.

In September 2024, U.S. intelligence revealed that Russia expanded its nuclear cooperation with Iran in exchange for short-range ballistic missiles for Ukraine. Israeli officials and experts have also voiced concerns that Russia may assist Iran with weaponization technology in response to Russian Security Council Deputy Chair Dmitry Medvedev’s provocative statement “It is worth considering which of the United States’ enemies we might potentially transfer our nuclear technologies to.”

Russian assistance could range from fuel fabrication to more sensitive areas such as metallurgy and weapons design. Moscow’s space launch vehicle cooperation with Iran may have allowed the countries to share critical missile technology, including advanced liquid rocket engines, that could be repurposed for ICBMs. Most concerning is the potential for Russia to help Iran improve its nuclear weapons designs and develop miniaturized warheads suitable for missile delivery systems.

In the near term, Iran seems to be more concerned with receiving Russian support for rebuilding its air defenses to protect its nuclear facilities. But its plans go beyond the immediate restoration of capabilities. Iranian President Masoud Pezeshkian visited Moscow days before the inauguration of Donald Trump, finalizing a long-awaited strategic partnership treaty with Russia that deepens bilateral cooperation. This timing is not coincidental—Iran seeks to counter a new U.S. administration’s promises of maximum pressure by cementing ties with Russia.

 

Don’t Go for Broke

Israel and the United States face a complex calculus on how to confront a weakened but nuclearizing Iran. For Israeli officials, an operational window of opportunity to attack Iran is currently open, because of Iran’s degraded air defenses. Moscow’s potential assistance to Iran in rebuilding and modernizing its air defenses will likely close this window, assuming that Russia manages to supply Iran with the more sophisticated air defense systems and advanced fighter jets it seeks.

Although the Trump administration’s mooted maximum pressure campaign might lead to calls for military action while constraining Tehran economically, an Israeli or joint U.S.-Israeli campaign could strengthen Iran’s nuclear resolve and deepen Russian support. Given the uncertainty of military success, a diplomatic approach combining tailored pressure with engagement offers a more promising path.

U.S. policymakers must thread the needle by calibrating pressure on both Moscow and Tehran without further deepening the existing partnership. The latest strategic partnership agreement shows the limits of current collaboration; it stops short of a mutual defense arrangement. Moreover, Russia’s own military needs in Ukraine cap the military exports that Russia can afford to send to Iran. This means the United States still has room to maneuver to limit Russian nuclear-related assistance to Iran. But policies from the first Trump administration, including maximum pressure and sanctions targeting Russia’s defense sector, paradoxically accelerated their cooperation by creating shared grievances and a common enemy. This time, the administration faces a more challenging dynamic. A better deal than the JCPOA is not possible. Iran’s nuclear program is more advanced than it was in 2015, which gives it more leverage in nuclear negotiations despite its weaker geopolitical position. Its partnership with Russia will help shield it from the worst of sanctions. And the first Trump administration’s decision to withdraw from the JCPOA may reasonably lead Tehran to believe that the United States will not provide any sanctions relief.

Washington should instead adopt a gradual approach, working with its European partners, France, Germany, and the United Kingdom, to trigger, or threaten to trigger, the snapback mechanism contained in the Iran deal, which would reimpose UN Security Council sanctions predating the JCPOA on Iran. Although Trump, who withdrew the United States from the deal unilaterally in 2018, may chafe at invoking the deal’s terms, administration officials, including Secretary of State Marco Rubio, have hinted at his support for imposing snapback sanctions. They could yet be a critical component in getting Iran to the negotiating table.

The expiration of the snapback mechanism in October 2025 gives the United States a time frame in which to reinvigorate diplomatic engagement and potentially extend or revise the deal’s terms. Despite no longer being a party to the nuclear deal, Washington should coordinate a carefully sequenced multilateral pressure campaign, taking advantage of the ability of France, Germany, and the United Kingdom to trigger the automatic reimposition of the pre-2015 sanctions, a process that neither Russia nor China can veto.

The United States should also actively encourage Israel to increase its support for Ukraine now that Russia’s leverage in Syria has diminished. In the past, Israel exercised caution in assisting Ukraine, supplying Kyiv with early warning radars and humanitarian aid but eschewing deeper cooperation, fearing retaliation against Russian Jews and the dissolution of the deconfliction channels with Russia in Syria. But after Assad’s ouster and Russia’s significant withdrawal from Syria, Israel may reconsider. Specific measures could include providing key enabling technologies such as mobile radar units and ammunition from seized stocks for legacy Soviet systems that Israel seized from Lebanon and Syria.

As long as the war in Ukraine grinds on and Iran’s acrimonious relations with the West persist, driving a wedge between Russia and Iran will be a lofty challenge. Washington must remain cognizant of potential Russian and Iranian efforts to reestablish influence in Syria, where the Russian-Iranian partnership first bore fruit. A nuclear Iran, with Russia’s backing, would further destabilize the moderate Sunni regimes in the region, embolden hard-liners, and weaken the emerging Sunni-Israeli axis, in addition to catapulting the area into a regional nuclear arms race. But the marriage of Putin’s isolated autocratic state with advanced nuclear capabilities and an Islamist regime intent on ensuring its own survival is a threat that would extend far beyond the Middle East. It may motivate like-minded states around the world to unite behind their discontent with the United States’ global leadership and join their ranks.

 

 

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