Thirteen years after the start of the Syrian uprising, the swift and dramatic fall of Bashar al-Assad shattered the perception of a stable, albeit repressive, status quo. For much of the past decade, Assad’s regime, bolstered by unwavering support from Iran and Russia, brutally suppressed dissent. What began as an uprising in 2011 evolved into a devastating civil war that eventually settled into an uneasy stalemate. Despite persistent challenges, Assad’s grip on power appeared secure. Yet his regime collapsed within days of the start of a coordinated rebel offensive.
Among other casualties was Iran’s influence in Syria, painstakingly cultivated through years of costly intervention and unwavering support. Tehran was Assad’s most steadfast ally throughout the conflict. Over the years, Iran invested immense resources and military aid to ensure his survival. Yet as the Syrian military rapidly disintegrated, Iran was notably absent. In the aftermath, Iran’s supreme leader, Ayatollah Ali Khamenei, condemned Assad’s fall as a foreign-orchestrated conspiracy, a framing that reflects Tehran’s efforts to preserve its image as a resilient regional power. Within Iran, however, officials and observers appear divided. The rapid pace of events and the depletion of Tehran’s military and political resources over the past year, amid escalating direct and indirect military confrontations with Israel, have left the leadership struggling to formulate a coherent response.
Iran’s strategic setback presents the United States with a unique opportunity to curb the potential for renewed conflict and to lay the groundwork for lasting stability in Syria. By continuing to support Syrian Kurdish forces, promoting dialogue among key Syrian stakeholders, and encouraging Israeli restraint in Syria, Washington can help shape the post-Assad reality into one of long-term peace and security. But stabilizing the region will also likely require Iran’s involvement in talks over Syria’s future. If Washington and Tehran fail to engage with each other, Syria will continue to suffer.
EXPOSED EXHAUSTION
Iran’s extensive involvement in Syria’s civil war was instrumental in sustaining the Assad regime. Since 2011, Tehran has spent somewhere between $30 billion and $50 billion on military aid, oil transfers, and logistical support to Syria. The Quds Force, the elite wing of Iran’s Islamic Revolutionary Guard Corps, coordinated operations early on by training local militias to reinforce the Syrian army and by mobilizing a wide array of foreign Shiite fighters, including members of the Lebanese organization Hezbollah, Iraqi militias, and Afghan and Pakistani groups.
After large-scale fighting subsided in 2018, Tehran began to focus on consolidating its influence in Syria’s south and southeast, securing control over territory and integrating the militias into the Syrian armed forces. But these efforts proved insufficient to prevent Assad’s rapid collapse in early December. Iran appears to have been misled by the façade of a capable and stable government in Damascus, even though Tehran itself had helped Assad craft this illusion. The Iranian government remained unprepared for the Syrian army’s swift collapse, as defensive lines crumbled and soldiers proved unready or unable to fight. In just a few days, rebels seized Syria’s second-largest city, Aleppo, and advanced southward, leaving Iran with no time to respond effectively. As IRGC Chief Commander Hossein Salami admitted, Iran “couldn’t fight on behalf of the Syrian army . . . when they were sitting idly by and watching.”
The weakening of Hezbollah further compounded Iran’s challenges. Hezbollah was central to Iran’s strategy in Syria, with thousands of its fighters deployed to support Assad’s regime over the last decade. After the death of the Quds Force commander Qasem Soleimani, in 2020, Hezbollah became the primary coordinator of Iranian-backed militias in Syria. But Israeli strikes against Hezbollah personnel and infrastructure over the last year wiped out leadership and prevented the group from offering Assad any further military or logistical support.
Israel also intensified its targeting of Iranian assets in Syria. Initially aimed at disrupting Iranian arms transfers to Hezbollah via Syria, this strategy became part of Israel’s broader confrontation with Hezbollah and the Iranian-backed “axis of resistance,” escalating into a de facto land and air blockade by late 2023 that effectively cut off Iranian troop and logistics movements into Syria, particularly through Iraq. Even Khamenei admitted in a speech in early December that Iran had been unable to provide Assad with support because every access point was effectively closed off.
Meanwhile, by the time the rebel offensive in Syria began, in late November, the Iraqi Shiite militias that had played a major role in the early stages of the Syrian civil war had become unwilling to reenter the fray, preoccupied with domestic priorities and wary of escalating costs of external intervention. This lack of reliable allied support left Iran constrained in its ability to respond effectively.
Domestic factors also influenced Tehran’s decisions not to engage. Two rounds of tit-for-tat with Israel, particularly a series of Israeli strikes on Iranian military sites and air defenses last October, had exposed the Islamic Republic’s vulnerabilities. And Iran’s economy is far less robust today than when Tehran first intervened in Syria in 2011, limiting its capacity to sustain another costly external engagement. Facing the likelihood of further escalation, Tehran prioritized fortifying its defenses over diverting resources to foreign conflicts.
A FRACTURING AXIS
The fall of Assad not only demonstrates Iran’s weaknesses but also poses significant new challenges for Tehran, threatening both its regional influence and the regime’s stability. Foremost among these is the difficulty of revitalizing Hezbollah’s operational capabilities. Syria long served as a vital logistical hub in the “land corridor” that linked Iran to the Mediterranean Sea and enabled the transfer of advanced weaponry and logistics to Hezbollah. With Assad’s collapse, this supply line has been severed, isolating Hezbollah and disrupting the axis of resistance’s geographical connectivity. Already weakened by a 14-month war with Israel, Hezbollah will now face the daunting task of recovering with far less direct logistical support from Iran.
Assad’s fall has also highlighted ideological and sectarian divisions among Iran’s allies that may further fracture the axis’s cohesion. Iran, Hezbollah, Iraqi militias, and the Houthis all viewed the event as a major setback. But Hamas and Palestinian Islamic Jihad, Sunni groups that Iran supports, congratulated the Syrian rebels of Hayat Tahrir al-Sham (HTS), a Sunni Islamist group, on their victory over Assad.
As far as the axis is concerned, losing Syria may also undermine Iran’s credibility with its regional partners in Iraq and Yemen. Iran’s failure to intervene decisively in Assad’s defense will likely raise doubts about its commitment and capacity. Former Iraqi Prime Minister Nouri al-Maliki, who maintained close ties to Iran, expressed his surprise over Tehran’s inaction in Syria during a television interview just after Assad’s fall. “I was surprised by . . . the position of those states that were on Syria’s side . . . Russia and Iran,” Maliki said. “How did they change [their position]? What are the consequences of this change?” Going forward, groups that have depended on Tehran’s support might now question its reliability
The loss of its ally in Syria will also disadvantage Iran in its rivalry with Turkey. Ankara’s strong support for Syrian rebels has disrupted the regional balance of power. Under Assad, Iran’s extensive presence in Syria allowed Tehran to counterbalance Turkey’s regional ambitions. But since Assad’s fall, Ankara—now the main patron of Syrian rebels, particularly HTS—has replaced Tehran and Moscow as the dominant external power in Syria, expanding the breadth of Turkey’s influence while limiting Iran’s. There are growing concerns in Iran that Turkey, emboldened by Tehran’s weakened position, could now seek to increase its influence, at Iran’s expense, in Iraq, Lebanon, and the South Caucasus. In Iraq and Lebanon, Turkey might bolster its support for Sunni factions against pro-Iranian Shiite groups. In the South Caucasus, Turkey’s push for the creation of the so-called Zangezur corridor—a strategic transit route linking Turkey to Azerbaijan via Armenian territory—threatens to cut Iran’s land access to Armenia, a strategic partner crucial for maintaining Tehran’s regional foothold and trade routes in the Caucasus, isolating it economically and geopolitically.
Finally, Assad’s fall has fueled domestic discontent among loyalists to the regime in Tehran, with some calling the loss a strategic blunder and openly criticizing the government on state television. For a regime heavily reliant on fervent supporters, such dissent poses a serious challenge. Moreover, there are fears that Sunni extremist groups in Iran’s restive southern regions, such as those populated by Arab and Baluchi groups, may be emboldened by the victory of like-minded groups in Syria, risking further unrest at a time when the government is increasingly vulnerable.
ONTO THE NEXT
Despite the many challenges facing Tehran, Iran is adapting its strategy to preserve influence in Syria and the Levant by making tactical adjustments. Iran has shown interest in engaging with Syrian Kurdish groups that, despite not challenging Assad directly, were among the key actors during the war, especially in the fight against Sunni extremist groups, and which retain control over large parts of northeastern Syria. In the lead-up to Assad’s ouster, Iranian-backed forces withdrew from key positions in eastern Syria, especially in the Deir ez‑Zor province near the Iraqi border, transferring control to the Syrian Democratic Forces, whose personnel and command structure are primarily Kurdish. This move signaled Iran’s effort to position itself as a potential partner to the Syrian Kurds, especially given Kurdish concerns that U.S. support for the SDF might diminish once Donald Trump returns to the White House. (Many expect Trump to reduce American involvement in Syria and to seek stronger ties with Turkey, which considers the SDF a terrorist group.)
Iran may also explore the possibility of engaging with HTS, leveraging the anti-Israeli and pro-Palestinian sentiments within the rebels’ ranks. Although the HTS leadership has expressed its unwillingness to start a conflict with Israel, ongoing Israeli strikes and territorial advances in Syria could encourage a change of heart. Tehran might offer support to HTS in exchange for strategic concessions, such as renewed access to Hezbollah forces in Lebanon.
Alternatively, Iran could pivot to forging new ties with Shiite and Alawite minorities in western Syria who fear discrimination and repression by Sunni extremists. By aligning with these groups, Iran could build a network of loyalist forces and proxies to sustain its influence in Syria even in the absence of a pliant ruling regime. Iran might even reorganize the hundreds of Assad regime soldiers that fled to Iraq into a counterrevolutionary force, potentially enabling it to regain a foothold in Syria.
FILLING THE VACUUM
The fall of Assad and the erosion of Iran’s foothold in Syria present a rare opportunity for renewal but also immense challenges, the resolution of which will require active U.S. engagement. First, sustained U.S. support for the Syrian Kurds is crucial. The Kurdish-led SDF has been a key ally in the fight against the Islamic State, the jihadi terrorist group also known as ISIS, and a stabilizing force in northeastern Syria. But recent clashes with Turkish-backed rebel groups have forced the SDF to suspend its operations against ISIS. Continued U.S. support, including financial, political, and diplomatic assistance, will strengthen the Kurds against such threats while deterring Iran from exploiting emerging power vacuums.
Washington must simultaneously encourage Israel to restrain and de-escalate its operations in southwestern Syria. Following Assad’s fall, Israel has expanded its presence beyond the Golan Heights, occupying areas deeper inside Syria and justifying the move by citing security concerns. But any prolonged Israeli occupation risks alienating Syrians and providing Iran with a pretext to reactivate its anti-Israel agenda in Syria.
The United States must also collaborate with allies in the Middle East and Europe to promote an inclusive political dialogue among all Syrian factions. The power vacuum left by Assad’s departure risks intensifying competition among various factions and among country’s many ethnic and religious minorities. Supporting comprehensive dialogue would help establish a representative government that preserves Syria’s territorial integrity and protects minority rights, while reducing the likelihood that Iran or other external actors exploit minority groups to gain influence.
Yet equally critical to ensuring security in Syria will be diplomatic efforts to prevent further destabilization in Iran. Tehran’s growing sense of insecurity following Assad’s fall may drive the country’s leadership to escalate activities that destabilize the region, such as efforts to further strengthen allied militias in Iraq and Yemen or inciting sectarian tensions in Syria. The United States should, in fact, offer Iran a seat at the table during regional talks over Syria’s future, addressing Tehran’s security concerns while calling on its leadership to de-escalate on other fronts. This strategy could curtail Iran’s disruptive influence in Syria and the greater Middle East—and possibly even open the door to more comprehensive diplomatic talks between Washington and Tehran.
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